C Language tutorials
Preparations for C Language
C is a procedural programming language. It was initially developed by Dennis Ritchie in the year 1972. It was mainly developed as a system programming language to write an operating system. The main features of C language include low-level access to memory, a simple set of keywords, and clean style, these features make C language suitable for system programmings like an operating system or compiler development.
Next to control 40 pins of Raspberry Pi via C language
Install WiringPi GPIO Library
We will control IO ports of Raspberry Pi by WiringPi GPIO library, let’s install WiringPi GPIO library.
Click the terminal icon of Raspberry Pi and open the terminal, as shown below:
Enter the following commands in the terminal and tap“Enter” cd /tmp
wget https://project-downloads.drogon.net/wiringpi-latest.deb
sudo dpkg -i wiringpi-latest.deb
As shown below：
Check the version of WiringPi GPIO library and corresponding definition of 40-pin headers
Input the following commands and press“Enter”
gpio -v
gpio readall
The version of WiringPi GPIO library is 2.52
Pins definition of WiringPi GPIO Library
(note: the silk mark of our extension board is defined by pins of BCM GPIO as well)
Run Example Code1
Copy the C_code.zip we provide to pi folder, and extract the example code from zip file, as shown below:
Double-click C_code folder to look through example code, as shown below:
Set the default editor of file with .c
Enter lesson1_Hello_World and right-click Open with…
Click Programming to select Geany Programmer’s Editor
Then, we can directly open file by doubl-click Geany Programmer’s Editor
The Use of Geany Programmer’s Editor
Open“HelloWorld.c”via it, click 
to compile code to check grammar errors.
Run Example Code
Terminal enters the corresponding courses，for example, enter lesson1_Hello_World.
Enter the route with terminal command:
cd /home/pi/C_code/lesson1_Hello_World
Input the compilation command:
gcc HelloWorld.c -o HelloWorld -lwiringPi
Input ls to check file of the current folder:
The compilation file:HelloWorld
Run a compilation file: HelloWorld
Input command：sudo ./HelloWorld(as shown below)
Command Explanation
You could select the folder and right-click to choose Openin the terminal as shown below, if you feel it complicated to enter the route.
Projects：
Note: G, - and GND marked on sensors and modules are so-called positive, which are connected to GND of GPIO extension board or “-” of breadboard; V、+、VCC are known as positive, which are interfaced 3V3 or 5V on extension board and“+”on breadboard.
Project 1：Hello World
Compile and Run the Example Code：
Input the following commands in the terminal, and press“Enter”:
cd /home/pi/C_code/lesson1_Hello_World
gcc HelloWorld.c -o HelloWorld -lwiringPi
sudo ./HelloWorld
Test Results：
Terminal prints Hello World ! , as shown below:
Example Code：
##include <wiringPi.h> //wiringPi GPIO library
##include <stdio.h> //standard input & output library
int main() //Main function, the entry of the program
{
wiringPiSetup(); //Initializes the wiringPi GPIO library
while(1) //An infinite loop
{
printf("Hello World!\n"); //\n is a newline print
delay(1000); //delay 1000ms
}
}
Project 2：LED Blinks
Description：
Let’s start from a rather basic and simple experiment—-LED Blinks.
Components：
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|---|---|---|---|---|---|---|
RaspberryPi*1 |
GPIO Extension Board*1 |
40pin Colorful Jumper Wires*1 |
Breadboard*1 |
LEDRed *1 |
220Ω Resistor*1 |
JumperWires |
LED: A light-emitting diode, the current is connected when anode(long pin) is connected to VCC, and cathode(short pin)is connected to GND. Its brightness is 2V and current is 6mA. LED must be connected to a resistor in the circuit, otherwise, the components will be burned.
Resistor: we use a carbon film resistor, 220Ωand its accuracy is 5%, why choose 220Ω resistor?
Since the high-level output voltage of GPIO pin of the Raspberry Pi is 3.3V, and the voltage of the LED is about 2V, and the current is about 6mA, we need to use a resistor to bear the voltage (3.3V-2V) = 1.3V, according to ohm The law: U/I = R knows: (3.3-2)/6 * 1000 ≈ 217Ω.
Breadboard: Below is a short instruction of breadboard. The holes on the board are connected. The inner board is structure diagram.
Schematic Diagram
Connection Diagram：
Since the PIN numbers of GPIO Extension Board and RPi GPIO are same, the part of breadboard and GPIO Extension Board is only shown on further connection diagram.
Working Principle：
The positive pole of LED is connected to GPIO18, when the pin of GPIO18 outputs 3.3V, LED will be on; when its pin outputs 0V, LED will be off.
Run Example Code
Input the following commands in the terminal and press“Enter”:
cd /home/pi/C_code/lesson2_LED_Blinking
gcc LED_Blinking.c -o LED_Blinking -lwiringPi
sudo ./LED_Blinking
Test Results：
Terminal prints and LED flashes.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
##include <wiringPi.h>
##include <stdio.h>
##define ledPin 1 //define led pin, BCM GPIO 18
int main()
{
wiringPiSetup(); //Initialize wiringPi
pinMode(ledPin,OUTPUT); //set the ledPin OUTPUT mode
while(1)
{
digitalWrite(ledPin,HIGH); //turn on led
printf("turn on the LED\n");
delay(500); //delay 500ms
digitalWrite(ledPin,LOW); //turn off led
printf("turn off the LED\n");
delay(500);
}
}
Project 3：SOS Light
Description：
S.O.S is a Morse code distress signal , used internationally, that was originally established for maritime use. We will present it with flashing LED.
Experiment Components:
Raspberry Pi*1
GPIO Extension Board*1
40 pin Colorful Jumper Wires*1
Breadboard*1
LED - Red *1
220Ω Resistor*1
Jumper Wires
Schematic Diagram
4. Connection Diagram：
Run Example Code
Input the following commands and press “Enter”:
cd /home/pi/C_code/lesson3_SOS
gcc SOS.c -o SOS -lwiringPi
sudo ./SOS
Test Results：
LED flashes quickly for three times, three times slowly and quickly three times, the terminal prints … _ _ _ …
Note: Press Ctrl + C on keyboard and exit code running.
Example Code:
##include <wiringPi.h>
##include <stdio.h> //The stdio.h header file defines three variable types,
//some macros, and various functions to perform input and output.
##define ledPin 1 //define led pin
int i1,i2,i3;
int main()
{
wiringPiSetup(); //Initialize wiringPi
pinMode(ledPin,OUTPUT); //set the ledPin OUTPUT mode
while(1)
{
while(i1<3)
{
digitalWrite(ledPin,HIGH); //turn on led
delay(100); //delay 100ms
digitalWrite(ledPin,LOW); //turn off led
delay(100);
i1 = i1 + 1;
printf(".\n");
}
while(i2<3)
{
digitalWrite(ledPin,HIGH); //turn on led
delay(1000); //delay 1000ms
digitalWrite(ledPin,LOW); //turn off led
delay(1000);
i2 = i2 + 1;
printf("-\n");
}
while(i3<3)
{
digitalWrite(ledPin,HIGH); //turn on led
delay(100); //delay 100ms
digitalWrite(ledPin,LOW); //turn off led
delay(100);
i3 = i3 + 1;
printf(".\n");
}
//clean
i1 = 0;
i2 = 0;
i3 = 0;
printf(" \n");
delay(500);
}
}
Project 4：Breathing LED
Description：
A“breathing LED” is a phenomenon where an LED’s brightness smoothly changes from dark to bright and back to dark, continuing to do so and giving the illusion of an LED“breathing.” This phenomenon is similar to a lung breathing in and out. So how to control LED’s brightness? We need to take advantage of PWM.
Experiment Components：
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|---|---|---|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
LED - Red *1 |
220ΩResistor *1 |
Jumper Wires |
Working Principle：
We use the PWM output of GPIO, PWM outputs analog signals and output value is 0~100 which is equivalent to output voltage 0~3.3V from GPIO port.
According to Ohm’s law: U/R = I, the resistance is 220Ω, and the value of voltage U changes, so does the value of current I, which can control the brightness of the LED lamp.
PWM (Pulse Width Modulation) is the control of the analog circuit through the digital output of microcomputer and a method that making digital coding on analog signal levels.
It sends square waves with certain frequency through digital pins, that is, high level and low level are output alternately for a period of time. Total time of each group high and low level is fixed, which is called cycle.
The time of high level output is pulse width whose percentage is called Duty Cycle. The longer that high level lasts, the larger the duty cycle of analog signals is, the corresponding voltage as well
Below chart is pulse width 50%, then the output voltage is 3.3 * 50% = 1.65V，the brightness of LED is medium.
In the experiment, we produce PWM via Wiringpi.
There are two ways outputting PWM on Wiringpi, one is PWM of Raspberry Pi(we recommend you to choose it if you want to control PWM correctly), the other is analog PWM of Wiring pi.
Schematic Diagram
Connection Diagram：
Run Example Code1：
PWM Output:
Input the following commands and press “Enter”:
cd /home/pi/C_code/lesson4_Breathing_LED
gcc Breathing_LED1.c -o Breathing_LED1 -lwiringPi
sudo ./Breathing_LED1
Test Results 1：
LED gradually brightens then darkens, in loop way.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code 1：
##include <stdio.h>
##include <wiringPi.h>
##define LED 1 //define led pin
int main(void)
{
int bright;
printf("Raspberry Pi wiringPi PWM test program\n");
wiringPiSetup(); //Initialize wiringPi
pinMode(LED,PWM_OUTPUT); //set the ledPin OUTPUT mode
while(1)
{
for (bright = 0; bright < 1024; ++bright) // pwm 0~1024
{
pwmWrite(LED,bright);
printf("bright:%d\n",bright); //%d is the integer output, bright is the variable to output
delay(10);
}
for (bright = 1023; bright >= 0; --bright)
{
pwmWrite(LED,bright);
printf("bright:%d\n",bright);
delay(10);
}
}
return 0;
}
Example Code 2：
Software simulates PWM output:
Input the following commands and press “Enter”:
cd /home/pi/C_code/lesson4_Breathing_LED
gcc Breathing_LED2.c -o Breathing_LED2 -lwiringPi
sudo ./Breathing_LED2
Test Results2：
LED gradually brightens then darkens, in loop way.
Note: Press Ctrl + C on keyboard and exit code running.
** Example Code 2：**
##include <stdio.h>
##include <wiringPi.h>
##include <softPwm.h> //Software PWM library
##define LED 1
int main(void)
{
int i = 0;
wiringPiSetup(); //Initialize wiringPi
softPwmCreate(LED, 0, 100); //Create pin LED as the PWM output(0~100)
while (1)
{
for(i=0; i<100; i++)
{
softPwmWrite(LED, i); //pwm write
delay(20);
printf("PWM = %d\n",i);
}
for(i=99; i>0; i--)
{
softPwmWrite(LED, i);
delay(20);
printf("PWM = %d\n",i);
}
}
return 0;
}
Project 5：Traffic Lights
Description：
In this lesson, we will learn how to control multiple LED lights and simulate the operation of traffic lights.
Traffic lights are signalling devices positioned at road intersections, pedestrian crossings, and other locations to control flows of traffic.
Green light on: Allows traffic to proceed in the direction denoted, if it is safe to do so and there is room on the other side of the intersection.
Red light: Prohibits any traffic from proceeding. A flashing red indication requires traffic to stop and then proceed when safe (equivalent to a stop sign).
Amber light (also known as ‘orange light’ or ‘yellow light’):
Warns that the signal is about to change to red, with some jurisdictions requiring drivers to stop if it is safe to do so, and others allowing drivers to go through the intersection if safe to do so.
Experiment Components：
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|---|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
LED - Red *1 |
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LED - Green*1 |
LED - Yellow*1 |
220Ω Resistor*3 |
Jumper Wires |
Schematic Diagram
Run Example Code
Input the following commands and press “Enter”:
cd /home/pi/C_code/lesson5_Traffic_Light
gcc Traffic_Light.c -o Traffic_Light -lwiringPi
sudo ./Traffic_Light
Test Results：
Note: Press Ctrl + C on keyboard and exit code running.
Red light is on 5s and off, yellow light flashes 3s and turn off, green light is lit for 5s and off, in a loop.
Example Code
##include <wiringPi.h>
##define R_pin 1 //BCM GPIO 18
##define G_pin 4 //BCM GPIO 24
##define Y_pin 5 //BCM GPIO 23
int main()
{
wiringPiSetup();
char j;
pinMode(R_pin,OUTPUT);
pinMode(G_pin,OUTPUT);
pinMode(Y_pin,OUTPUT);
digitalWrite(R_pin, LOW);
digitalWrite(G_pin, LOW);
digitalWrite(Y_pin, LOW);
while(1)
{
digitalWrite(R_pin, HIGH);//// turn on red LED
delay(5000);// wait 5 seconds
digitalWrite(R_pin, LOW); // turn off red LED
for(j=0;j<3;j++) // blinks for 3 times
{
digitalWrite(G_pin, HIGH);// turn on yellow LED
delay(500);// wait 0.5 second
digitalWrite(G_pin, LOW);// turn off yellow LED
delay(500);// wait 0.5 second
}
digitalWrite(Y_pin, HIGH);// turn on green LED
delay(5000);// wait 5 second
digitalWrite(Y_pin, LOW);// turn off green LED
}
}
Project 6：RGB Light
Description：
In this chapter, we will demonstrate how RGB lights show different colors via programming.
Experiment Components：
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|---|---|---|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin ColorfulJumper Wires*1 |
Breadboard*1 |
RGB - LED *1 |
100Ω Resistor*3 |
Jumper Wires |
Component Knowledge：
We use common cathode RGB lights.
Working Principle：
RGB LED integrated three LEDs emitting red,green and blue light. It has 4 pins，long pin (-) is a shared pin, that is, the negative port of 3LED, as shown below, we control three LEDs to emit light with different brightness to make RGB show different colors.
Red, green and blue are three primary colors. They could produce all kinds of visible lights when mixing them up. Computer screen, single pixel mobile phone screen, neon light work under this principle.
Next, we will make a RGB LED displaying all kinds of colors.
Schematic Diagram
Example Code
Input the following commands and press “Enter”:
cd /home/pi/C_code/lesson6_RGB_LED
gcc RGB_LED.c -o RGB_LED -lwiringPi
sudo ./RGB_LED
Test Results：
RGB lights show colors randomly.
Note: Press Ctrl + C on keyboard and exit code running.
RGB light shows the all kinds of colors randomly.
Example Code
##include <stdio.h>
##include <stdlib.h>
##include <stdint.h>
##include <wiringPi.h>
##include <softPwm.h>
##include <time.h>
##define pin_R 5 //BCM GPIO 24
##define pin_G 4 //BCM GPIO 23
##define pin_B 1 //BCM GPIO 18
int main(void){
int red,green,blue;
if (wiringPiSetup() == -1){
printf("Setup GPIO error!\n");
return -1;
}
softPwmCreate(pin_R, 0, 100);
softPwmCreate(pin_G, 0, 100);
softPwmCreate(pin_B, 0, 100);
while (1){
srand((unsigned)time(NULL));
red = rand()%101 + 0;
green = rand()%101 + 0;
blue = rand()%101 + 0;
softPwmWrite(pin_R, red);
softPwmWrite(pin_G, green);
softPwmWrite(pin_B, blue);
delay(100);
}
return 0;
}
Project 7：Flow Light
1Description：
What is flow light? Maybe you see it on the wall of buildings and billboards. It is a scene that LED gradually brightens then darkens one by one.
Experiment Components：
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|---|---|---|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
LED - Red *8 |
220Ω Resistor*8 |
Jumper Wires |
Schematic Diagram
Example Code
Input the following commands and press “Enter”:
cd /home/pi/C_code/lesson7_LED_Chasing_Effect
gcc LED_Chasing_Effect.c -o LED_Chasing_Effect -lwiringPi
sudo ./LED_Chasing_Effect
Test Results：
Eight LED lights change from light to dark then back to dark, one by one.
Note: Press Ctrl + C on keyboard and exit code runningNote: press Ctrl + C to exit the code.
6.Example Code:
##include <wiringPi.h>
##define led1 1 //BCM GPIO 18
##define led2 4 //BCM GPIO 23
##define led3 5 //BCM GPIO 24
##define led4 6 //BCM GPIO 25
##define led5 26 //BCM GPIO 12
##define led6 27 //BCM GPIO 16
##define led7 28 //BCM GPIO 20
##define led8 29 //BCM GPIO 21
int main()
{
wiringPiSetup();
pinMode(led1,OUTPUT); //set pin OUTPUT mode
pinMode(led2,OUTPUT);
pinMode(led3,OUTPUT);
pinMode(led4,OUTPUT);
pinMode(led5,OUTPUT);
pinMode(led6,OUTPUT);
pinMode(led7,OUTPUT);
pinMode(led8,OUTPUT);
digitalWrite(led1, LOW); //set pin LOW
digitalWrite(led2, LOW);
digitalWrite(led3, LOW);
digitalWrite(led4, LOW);
digitalWrite(led5, LOW);
digitalWrite(led6, LOW);
digitalWrite(led7, LOW);
digitalWrite(led8, LOW);
while(1)
{
//Light up one by one
digitalWrite(led1, HIGH);
delay(200);
digitalWrite(led2, HIGH);
delay(200);
digitalWrite(led3, HIGH);
delay(200);
digitalWrite(led4, HIGH);
delay(200);
digitalWrite(led5, HIGH);
delay(200);
digitalWrite(led6, HIGH);
delay(200);
digitalWrite(led7, HIGH);
delay(200);
digitalWrite(led8, HIGH);
delay(200);
//Turn off one by one
digitalWrite(led1, LOW);
delay(200);
digitalWrite(led2, LOW);
delay(200);
digitalWrite(led3, LOW);
delay(200);
digitalWrite(led4, LOW);
delay(200);
digitalWrite(led5, LOW);
delay(200);
digitalWrite(led6, LOW);
delay(200);
digitalWrite(led7, LOW);
delay(200);
digitalWrite(led8, LOW);
delay(200);
}
}
Project 8：Doorbell
Description：
In this project, we will demonstrate how doorbell works.
Experiment Components:
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|---|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
Active Buzzer *1 |
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||
Jumper Wires |
10KΩ Resistor*1 |
Button Switch *1 |
Components Knowledge:
Active buzzer：
An active buzzer will generate a tone using an internal oscillator, so all that is needed is a DC voltage. A passive buzzer requires an AC signal to make a sound. It is like an electromagnetic speaker, where a changing input signal produces the sound, rather than producing a tone automatically.
As a type of electronic buzzer with integrated structure, buzzers, which are supplied by DC power, are widely used in computers, printers, photocopiers, alarms, electronic toys, automotive electronic devices, telephones, timers and other electronic products for voice devices. Buzzers can be categorized as active and passive ones (see the following picture). Turn the pins of two buzzers face up, and the one with a green circuit board is a passive buzzer, while the other enclosed with a black tape is an active one.
Button switch: it can control circuit. Before pressed, the current can’t pass from one end to the other end. Both ends are like two mountains. There is a river in between. We can’t cross this mountain to another mountain. When pressed, my internal metal piece is
connecting the two sides to let the current pass, just like building a bridge to connect the two mountains.
Inner structure:
, 1 and 1 , 2 and 2 are connected , however, 1 and 2 are disconnected when the button is not pressed; 1 and 2 are connected when pressing the button.
10KΩ resistor：
It is pull-up resistor. The high and low levels of Raspberry Pi will be unstable if connecting only GPIO pins instead of resistors.
Resistor could stabilize the electronic signal and protect circuit.
The circuit will be shorten and components will be burnt if without wiring 10kΩ resistor, as shown below;
Schematic Diagram：
Run Example Code：
Input the following commands and press “Enter”:
cd /home/pi/C_code/lesson8_Active_Buzzer
gcc Active_Buzzer.c -o Active_Buzzer -lwiringPi
sudo ./Active_Buzzer
Test Results：
Press button, the buzzer emits sound, otherwise, it doesn’t.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
##include <wiringPi.h>
##include <stdio.h>
##define button 1 //button pin BCM GPIO 18
##define buzzer 2 //buzzer pin BCM GPIO 27
int main()
{
wiringPiSetup();
char val;
{
pinMode(button,INPUT); //set the button pin INPUT mode
pinMode(buzzer,OUTPUT);
}
while(1)
{
val=digitalRead(button); // digital read
printf("val = %d\n", val);
if(val==0)//check if the button is pressed, if yes, turn on the Buzzer
digitalWrite(buzzer,HIGH); //The buzzer made a sound
else
digitalWrite(buzzer,LOW);
}
}
Project 9：Passive Buzzer
Description：
We will conduct an interesting experiment—–control passive buzzer to compose a song.
Experiment Components：
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|---|---|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
Passive Buzzer *1 |
Jumper Wires |
Component Knowledge：
Passive buzzer：
Passive buzzer is a type of electronic buzzer with integrated structure.
Buzzers can be categorized as active and passive ones (see the following picture).
An active buzzer has a built-in oscillating source, so it will make sounds when electrified. But a passive buzzer does not have such source, so it will not tweet if DC signals are used; instead, you need to use square waves whose frequency is between 2K and 5K to drive it. The active buzzer is often more expensive than the passive one because of multiple built-in oscillating circuits.
Turn the pins of two buzzers face up, and the one with a green circuit board is a passive buzzer, while the other enclosed with a black tape is an active one, as shown：
Passive buzzer provides alternating current to sound coils to make electronic magnet and permanent magnet attraction or repulsion so as to push vibration film to emit sound, according to electromagnetic induction.
Only certain frequency with high and low levels can make passive buzzer emit sound, since DC current only makes vibration film vibrated continuously rather than producing sound.
Schematic and Connection Diagram
Run Example Code1：
Input the following commands and press “Enter”:
cd /home/pi/C_code/lesson9_Passive_Buzzer
gcc Passive_Buzzer1.c -o Passive_Buzzer1 -lwiringPi
sudo ./Passive_Buzzer1
Test Results1：
Passive buzzer emits“do、re、mi、fa、sol、la、si”.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code1：
##include <stdio.h>
##include <stdlib.h>
##include <stdint.h>
##include <wiringPi.h>
##define buzPin 1 //BCM GPIO 18
void init()
{
if (wiringPiSetup () == -1)
exit (1) ;
pinMode(buzPin, PWM_OUTPUT); //Set the pin to PWM output mode
pwmSetMode(PWM_MODE_MS); // Set PWM signal mode to MS mode
pwmSetClock(32); // Set the clock base frequency to 19.2m /32=600KHZ
}
void beep(int freq,int t_ms)
{
int range;
if(freq<100||freq>1000)
{
printf("invalid freq");
return;
}
// Set the range to 600KHZ/ Freq. That is,
//the freQ frequency period is composed of the range of 1/600khz.
range=600000/freq;
pwmSetRange(range);
pwmWrite(buzPin,range/2); // Set the duty cycle to 50%.
if(t_ms>0)
{
delay(t_ms);
}
}
int main()
{
wiringPiSetup();
init();
while(1)
{
beep(262,300); //Frequency and time
printf("do\n");
beep(294,300);
printf("re\n");
beep(330,300);
printf("mi\n");
beep(349,300);
printf("fa\n");
beep(392,300);
printf("so\n");
beep(440,300);
printf("la\n");
beep(494,300);
printf("si\n");
beep(523,300);
printf("Do\n");
pwmWrite(buzPin,0); //turn off the buzzer
delay(2000);
}
}
Run Example Code2：
Input the following commands and press “Enter”:
cd /home/pi/C_code/lesson9_Passive_Buzzer
gcc Passive_Buzzer2.c -o Passive_Buzzer2 -lwiringPi
sudo ./Passive_Buzzer2
Test Results2：
Passive buzzer plays a “Happy Birthday”song.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code2：
##include <stdio.h>
##include <stdlib.h>
##include <stdint.h>
##include <wiringPi.h>
##define Do 262
##define Re 294
##define Mi 330
##define Fa 349
##define Sol 392
##define La 440
##define Si 494
##define Do_h 532
##define Re_h 587
##define Mi_h 659
##define Fa_h 698
##define Sol_h 784
##define La_h 880
##define Si_h 988
##define buzPin 1 //buzzer pin BCM GPIO 18
//The tones
int song_1[]=
{
Sol,Sol,La,Sol,Do_h,Si,
Sol,Sol,La,Sol,Re_h,Do_h,
Sol,Sol,Sol_h,Mi_h,Do_h,Si,La,
Fa_h,Fa_h,Mi_h,Do_h,Re_h,Do_h
};
//To the beat
float beat_1[]=
{
0.5,0.5,1,1,1,1+1,
0.5,0.5,1,1,1,1+1,
0.5,0.5,1,1,1,1,1,
0.5,0.5,1,1,1,1+1
};
int length;
int x;
void init()
{
if (wiringPiSetup () == -1)
exit (1) ;
pinMode(buzPin, PWM_OUTPUT); //Set the pin to PWM output mode
pwmSetMode(PWM_MODE_MS); // Set PWM signal mode to MS mode
pwmSetClock(32); // Set the clock base frequency to 19.2m /32=600KHZ
}
void beep(int freq,int t_ms)
{
int range;
if(freq<100||freq>1000)
{
printf("invalid freq");
return;
}
// Set the range to 600KHZ/ Freq. That is,
//the freQ frequency period is composed of the range of 1/600khz.
range=600000/freq;
pwmSetRange(range);
pwmWrite(buzPin,range/2); // Set the duty cycle to 50%.
if(t_ms>0)
{
delay(t_ms);
}
}
int main()
{
wiringPiSetup();
init();
length=sizeof(song_1)/sizeof(song_1[0]); //Number of tones
while(1)
{
for(x=0;x<length;x++) //play
{
beep(song_1[x],500*beat_1[x]);
}
pwmWrite(buzPin,0); //turn off buzzer
delay(2000);
}
}
Project 10：1-Digit 7 Segment LED Display
Description：
In this lesson, let’s learn how to control LED display.
Experiment Components：
|
|
|
|
|
|
|
|---|---|---|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
1-digit 7-seg LED*1 |
220ΩResistor*8 |
Jumper Wires |
Component Knowledge：
LED display：
LED segment display is a semiconductor light-emitting device. Its basic unit is a light-emitting diode (LED).
For the common anode display, connect the common anode (COM) to +5V. When the cathode level of a certain segment is low, the segment is on; when the cathode level of a certain segment is high, the segment is off.
For the common cathode display, connect the common cathode (COM) to GND. When the anode level of a certain segment is high, the segment is on; when the anode level of a certain segment is low, the segment is off.
Each segment of the display consists of an LED. So when you use it, you also need to use a current-limiting resistor. Otherwise, LED will be burnt out.
When using 1-digit 7-segment display please notice that if it is common anode, the common anode pin connects to the power source; if it is common cathode, the common cathode pin connects to the GND.
Each of the LEDs in the display is given a positional segment with one of its connection pins led out from the rectangular plastic package. These LED pins are labeled from “a” through to “g” representing each individual LED.
Below is the seven-segment pin diagram.
Schematic Diagram：
Run Example Code：
Input the following commands and press “Enter”:
cd /home/pi/C_code/lesson10_1_digit_LED_Segment_Display
gcc 1_digit_LED_Segment_Display.c -o 1_digit_LED_Segment_Display -lwiringPi
sudo ./1_digit_LED_Segment_Display
Test Results：
LED display shows0~9，in loop way.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
##include <wiringPi.h>
//led pin
int a=4; //GPIO23
int b=1; //GPIO18
int c=22; //GPIO6
int d=23; //GPIO13
int e=24; //GPIO19
int f=5; // GPIO24
int g=6; //GPIO25
int dp=21; //GPIO5
int i;
void digital_0()//0
{
digitalWrite(a,HIGH);
digitalWrite(b,HIGH);
digitalWrite(c,HIGH);
digitalWrite(d,HIGH);
digitalWrite(e,HIGH);
digitalWrite(f,HIGH);
digitalWrite(g,LOW);
digitalWrite(dp,LOW);
}
void digital_1()//1
{
digitalWrite(a,LOW);
digitalWrite(b,HIGH);
digitalWrite(c,HIGH);
digitalWrite(d,LOW);
digitalWrite(e,LOW);
digitalWrite(f,LOW);
digitalWrite(g,LOW);
digitalWrite(dp,LOW);
}
void digital_2()//2
{
digitalWrite(a,HIGH);
digitalWrite(b,HIGH);
digitalWrite(c,LOW);
digitalWrite(d,HIGH);
digitalWrite(e,HIGH);
digitalWrite(f,LOW);
digitalWrite(g,HIGH);
digitalWrite(dp,LOW);
}
void digital_3()//3
{
digitalWrite(a,HIGH);
digitalWrite(b,HIGH);
digitalWrite(c,HIGH);
digitalWrite(d,HIGH);
digitalWrite(e,LOW);
digitalWrite(f,LOW);
digitalWrite(g,HIGH);
digitalWrite(dp,LOW);
}
void digital_4()//4
{
digitalWrite(a,LOW);
digitalWrite(b,HIGH);
digitalWrite(c,HIGH);
digitalWrite(d,LOW);
digitalWrite(e,LOW);
digitalWrite(f,HIGH);
digitalWrite(g,HIGH);
digitalWrite(dp,LOW);
}
void digital_5()//5
{
digitalWrite(a,HIGH);
digitalWrite(b,LOW);
digitalWrite(c,HIGH);
digitalWrite(d,HIGH);
digitalWrite(e,LOW);
digitalWrite(f,HIGH);
digitalWrite(g,HIGH);
digitalWrite(dp,LOW);
digitalWrite(e,LOW);
}
void digital_6()//6
{
digitalWrite(a,HIGH);
digitalWrite(b,LOW);
digitalWrite(c,HIGH);
digitalWrite(d,HIGH);
digitalWrite(e,HIGH);
digitalWrite(f,HIGH);
digitalWrite(g,HIGH);
digitalWrite(dp,LOW);
}
void digital_7()//7
{
digitalWrite(a,HIGH);
digitalWrite(b,HIGH);
digitalWrite(c,HIGH);
digitalWrite(d,LOW);
digitalWrite(e,LOW);
digitalWrite(f,LOW);
digitalWrite(g,LOW);
digitalWrite(dp,LOW);
}
void digital_8()//8
{
digitalWrite(a,HIGH);
digitalWrite(b,HIGH);
digitalWrite(c,HIGH);
digitalWrite(d,HIGH);
digitalWrite(e,HIGH);
digitalWrite(f,HIGH);
digitalWrite(g,HIGH);
digitalWrite(dp,LOW);
}
void digital_9()//9
{
digitalWrite(a,HIGH);
digitalWrite(b,HIGH);
digitalWrite(c,HIGH);
digitalWrite(d,HIGH);
digitalWrite(e,LOW);
digitalWrite(f,HIGH);
digitalWrite(g,HIGH);
digitalWrite(dp,LOW);
}
int main()
{
wiringPiSetup();
for(i=22;i<=29;i++)
{
pinMode(i,OUTPUT);
}
while(1)
{
digital_0();//0
delay(1000);
digital_1();//1
delay(1000);
digital_2();//2
delay(1000);
digital_3();//3
delay(1000);
digital_4();//4
delay(1000);
digital_5();//5
delay(1000);
digital_6();//6
delay(1000);
digital_7();//7
delay(1000);
digital_8();//8
delay(1000);
digital_9();//9
delay(1000);
}
}
Project 11：4-Digit LED Display
Description：
In previous lesson, the LED display only shows 1 digit number, whereas, we could try to operate 4 digit LED display.
Experiment Components：
|
|
|
|
|
|
|
|---|---|---|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
4-digit 7-seg LED*1 |
220Ω Resistor*8 |
Jumper Wires |
Component Knowledge：
4-digit LED display:
The 4-digit LED display is divided into common anode and common cathode. Similar to 1-digit segment LED display, it is controlled display segment by 8 GPIO ports(8 LED lights). However, this is 4 digit display, 4 GPIO ports are required to control the bit selection terminal.
Ours is common cathode
4-digit LED Display Pinout
Pin 1, 2, 3 and 4 are control pin of control bit
Schematic Diagram
Run Example Code：
Input the following commands and press “Enter”:
cd /home/pi/C_code/lesson11_4_digit_LED_Segment_Display
gcc 4_digit_LED_Segment_Display.c -o 4_digit_LED_Segment_Display -lwiringPi
sudo ./4_digit_LED_Segment_Display
Test Results：
4-digit LED display firstly shows“0000”, then plus 1 every time until it reaches“9999”, however, when “9999” adds 1, the value changes into“0000”.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
##include <wiringPi.h>
int a = 5;// GPIO24
int b = 1; // GPIO18
int c = 22;// GPIO6
int d = 24;// GPIO19
int e = 25;// GPIO26
int f = 4;// GPIO23
int g = 21;// GPIO5
int dp = 23;// GPIO13
int d4 = 3;// GPIO22
int d3 = 2;// GPIO27
int d2 = 0;// GPIO17
int d1 = 7;// GPIO4
// set variable
long n = 1230;
int x = 100;
int del = 55; // fine adjustment for clock
void WeiXuan(unsigned char n)//
{
switch (n)
{
case 1:
digitalWrite(d1, LOW);
digitalWrite(d2, HIGH);
digitalWrite(d3, HIGH);
digitalWrite(d4, HIGH);
break;
case 2:
digitalWrite(d1, HIGH);
digitalWrite(d2, LOW);
digitalWrite(d3, HIGH);
digitalWrite(d4, HIGH);
break;
case 3:
digitalWrite(d1, HIGH);
digitalWrite(d2, HIGH);
digitalWrite(d3, LOW);
digitalWrite(d4, HIGH);
break;
case 4:
digitalWrite(d1, HIGH);
digitalWrite(d2, HIGH);
digitalWrite(d3, HIGH);
digitalWrite(d4, LOW);
break;
default :
digitalWrite(d1, HIGH);
digitalWrite(d2, HIGH);
digitalWrite(d3, HIGH);
digitalWrite(d4, HIGH);
break;
}
}
void Num_0()
{
digitalWrite(a, HIGH);
digitalWrite(b, HIGH);
digitalWrite(c, HIGH);
digitalWrite(d, HIGH);
digitalWrite(e, HIGH);
digitalWrite(f, HIGH);
digitalWrite(g, LOW);
digitalWrite(dp, LOW);
}
void Num_1()
{
digitalWrite(a, LOW);
digitalWrite(b, HIGH);
digitalWrite(c, HIGH);
digitalWrite(d, LOW);
digitalWrite(e, LOW);
digitalWrite(f, LOW);
digitalWrite(g, LOW);
digitalWrite(dp, LOW);
}
void Num_2()
{
digitalWrite(a, HIGH);
digitalWrite(b, HIGH);
digitalWrite(c, LOW);
digitalWrite(d, HIGH);
digitalWrite(e, HIGH);
digitalWrite(f, LOW);
digitalWrite(g, HIGH);
digitalWrite(dp, LOW);
}
void Num_3()
{
digitalWrite(a, HIGH);
digitalWrite(b, HIGH);
digitalWrite(c, HIGH);
digitalWrite(d, HIGH);
digitalWrite(e, LOW);
digitalWrite(f, LOW);
digitalWrite(g, HIGH);
digitalWrite(dp, LOW);
}
void Num_4()
{
digitalWrite(a, LOW);
digitalWrite(b, HIGH);
digitalWrite(c, HIGH);
digitalWrite(d, LOW);
digitalWrite(e, LOW);
digitalWrite(f, HIGH);
digitalWrite(g, HIGH);
digitalWrite(dp, LOW);
}
void Num_5()
{
digitalWrite(a, HIGH);
digitalWrite(b, LOW);
digitalWrite(c, HIGH);
digitalWrite(d, HIGH);
digitalWrite(e, LOW);
digitalWrite(f, HIGH);
digitalWrite(g, HIGH);
digitalWrite(dp, LOW);
}
void Num_6()
{
digitalWrite(a, HIGH);
digitalWrite(b, LOW);
digitalWrite(c, HIGH);
digitalWrite(d, HIGH);
digitalWrite(e, HIGH);
digitalWrite(f, HIGH);
digitalWrite(g, HIGH);
digitalWrite(dp, LOW);
}
void Num_7()
{
digitalWrite(a, HIGH);
digitalWrite(b, HIGH);
digitalWrite(c, HIGH);
digitalWrite(d, LOW);
digitalWrite(e, LOW);
digitalWrite(f, LOW);
digitalWrite(g, LOW);
digitalWrite(dp, LOW);
}
void Num_8()
{
digitalWrite(a, HIGH);
digitalWrite(b, HIGH);
digitalWrite(c, HIGH);
digitalWrite(d, HIGH);
digitalWrite(e, HIGH);
digitalWrite(f, HIGH);
digitalWrite(g, HIGH);
digitalWrite(dp, LOW);
}
void Num_9()
{
digitalWrite(a, HIGH);
digitalWrite(b, HIGH);
digitalWrite(c, HIGH);
digitalWrite(d, HIGH);
digitalWrite(e, LOW);
digitalWrite(f, HIGH);
digitalWrite(g, HIGH);
digitalWrite(dp, LOW);
}
void Clear() // clear the screen
{
digitalWrite(a, LOW);
digitalWrite(b, LOW);
digitalWrite(c, LOW);
digitalWrite(d, LOW);
digitalWrite(e, LOW);
digitalWrite(f, LOW);
digitalWrite(g, LOW);
digitalWrite(dp, LOW);
}
void pickNumber(unsigned char n)// select number
{
switch (n)
{
case 0: Num_0();
break;
case 1: Num_1();
break;
case 2: Num_2();
break;
case 3: Num_3();
break;
case 4: Num_4();
break;
case 5: Num_5();
break;
case 6: Num_6();
break;
case 7: Num_7();
break;
case 8: Num_8();
break;
case 9: Num_9();
break;
default: Clear();
break;
}
}
void Display(unsigned char x, unsigned char Number)// take x as coordinate and display number
{
WeiXuan(x);
pickNumber(Number);
delay(1);
Clear() ; // clear the screen
}
int i;
int main()
{
wiringPiSetup();
for(i=0;i<=7;i++) //set pin OUTPUT mode
{
pinMode(i,OUTPUT);
}
for(i=21;i<=29;i++)
{
pinMode(i,OUTPUT);
}
while(1)
{
int w=0;
int s=0;
int y=0;
int z=0;
unsigned long currentMillis = millis(); //The time it takes the program to run here
while(z>=0)
{
while(millis()-currentMillis<1000) //Refresh once a second
{
Display(1,w);
Display(2,s);
Display(3,y);
Display(4,z);
}
currentMillis = millis();
z++; // The units digit automatically adds 1
if (z>9) //If the units digit is greater than 9
{
y++; //Ten digit plus 1
z=0; //Let's clear the units digit 0
}
if (y>9)
{
s++;
y=0;
}
if (s>9)
{
w++;
s=0;
}
if (w>9)
{
w=0;
s=0;
y=0;
z=0;
}
}
}
}
Knowledge：
Project 12：8*8 Dot Matrix
Description：
In this chapter, let’s get down with a 8x8 LED dot matrix.
Experiment Components：
|
|
|
|
|
|
|
|---|---|---|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
88 LED Matrix1 |
220ΩResistor*8 |
Jumper Wires |
Component Knowledge：
8*8 LED Matrix：
8×8 matrix consists of 64 dots or pixels. There is a LED for each pixel and these LEDs are connected to total of 16 pins.
Generally, there are two types of dot matrix – common cathode and common anode.
Pic 1
Pic 2
Schematic Diagram：
Working Principle：
8*8 is composed of LEDs. It will turn on if the positive is high level and negative is low level.
For the above figure, the first LED will be on if setting Y0(0) to HIGH and the rest of pins to LOW, X0(A) to LOW and the rest one to HIGH.
Run Example Code：
Input the following commands and press “Enter”:
cd /home/pi/C_code/lesson12_LED_Matrix
gcc LED_Matrix.c -o LED_Matrix -lwiringPi
sudo ./LED_Matrix
Test Results：
The dot on 8*8 dot matrix module gradually turns on until to full screen and then off.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
##include <wiringPi.h>
int y[8]={2,7,21,0,25,22,24,23}; //Y direction pin
int x[8]={5,27,28,1,29,4,6,26}; //X direction pin
int main()
{
wiringPiSetup();
char i;
char j;
for(i=0;i<8;i++) //Set both XY pins to output mode
{
pinMode(y[i],OUTPUT);
pinMode(x[i],OUTPUT);
}
while(1)
{
for(j=0;j<8;j++)
{
digitalWrite(x[j], LOW);// set I/O pins as low
}
for(i=0;i<8;i++)
{
digitalWrite(y[i], HIGH);// set I/O pins as high
delay(200); // delay
}
for(i=0;i<8;i++)
{
digitalWrite(y[i], LOW);// set I/O pins as low
delay(200); // delay
}
}
}
Project 13：74HC595
Description：
In previous lesson, we control a 1-digit LED display with eight, which is wasteful. We need to figure out a method to save the use of GPIO ports. In fact, we need a 74HC595 CHIP.
Experiment Components：
|
|
|
|
|
|---|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
1-digit 7- seg LED*1 |
|
|
|
||
220Ω Resistor*8 |
74HC595N*1 |
Jumper Wires |
Component Knowledge：
74HC595：
The 74HC595 consists of an 8−bit shift register and an 8−bit D−typelatch with three−state parallel outputs. The shift register accepts serial data and provides a serial output. The shift register also provides parallel data to the 8−bit latch. The shift register and latch have independent clock inputs. This device also has an asynchronous reset for the shift register.
74HC595 Pinout：
74HC595 Control Protocol
13 PIN OE |
Enable pin, not controlled by program when high level; make it connect to GND when low level |
|---|---|
14 PIN SI |
This is pin receiving data, enter a bit each time and compose a byte if inputting eight times |
10 PIN SCLK |
Shift register clear pin, used to clear out all data in shift register, when low level, data will be cleared out. |
11 PIN SCK |
Clock pin of shift register, the data inside will move backward and receive the data input when it is on rising edge. |
12 PIN RCK |
Clock input pin of latch register, data from shift register will saved in latch register when it is on rising edge. The data will be output from QA~QH |
9 Pin SQH |
Cascade pin，connected to multiple 74HC595 chips |
More details about 74HC595 chip, you could look through chip specification folder
Schematic Diagram：
The output end QA~QH of 74HC595 respond to the pin DP, and g~a.
Why? Since the binary is counted from the right, programming will be convenient. For example, 1-digit display shows 0011 1111 , the first bit is 1 which equals to QA saved in 74HC595, then when the rest numbers are sent to 74HC595, 1 will be pushed to QH, and last bit 0 is placed on QA. However, the wiring is so inverse that the first bit of binary corresponds to a and last one to DIP controlling 1-digit display.
74HC595 |
|||||||||
|---|---|---|---|---|---|---|---|---|---|
QH |
QG |
QF |
QE |
QD |
QC |
QB |
QA |
||
a |
b |
c |
d |
e |
f |
g |
dp |
||
0 |
1 |
1 |
1 |
1 |
1 |
1 |
0 |
0 |
252 |
1 |
0 |
1 |
1 |
0 |
0 |
0 |
0 |
0 |
96 |
2 |
1 |
1 |
0 |
1 |
1 |
0 |
1 |
0 |
218 |
3 |
1 |
1 |
1 |
1 |
0 |
0 |
1 |
0 |
242 |
4 |
0 |
1 |
1 |
0 |
0 |
1 |
1 |
0 |
102 |
5 |
1 |
0 |
1 |
1 |
0 |
1 |
1 |
0 |
182 |
6 |
1 |
0 |
1 |
1 |
1 |
1 |
1 |
0 |
190 |
7 |
1 |
1 |
1 |
0 |
0 |
0 |
0 |
0 |
224 |
8 |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
0 |
254 |
9 |
1 |
1 |
1 |
1 |
0 |
1 |
1 |
0 |
246 |
Run Example Code：
Input the following commands and press “Enter”:
cd /home/pi/C_code/lesson13_74HC595
gcc 74HC595.c -o 74HC595 -lwiringPi
sudo ./74HC595
Test Results：
LED display shows 0~9.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
##include <wiringPi.h>
##include <wiringShift.h>
int dataPin = 0; //define three pins BCM GPIO 17
int latchPin = 2; //BCM GPIO 22
int clockPin = 3; //BCM GPIO 27
int a[10]={252,96,218,242,102,182,190,224,254,246};
int x;
int main()
{
wiringPiSetup();
{
pinMode(latchPin,OUTPUT);
pinMode(clockPin,OUTPUT);
pinMode(dataPin,OUTPUT); //three pins as output
}
while(1)
{
for(x=0; x<10 ;x++ ) //calculate counting function
{
digitalWrite(latchPin,LOW);
shiftOut(dataPin,clockPin,MSBFIRST,a[x]); //display array a[x]
digitalWrite(latchPin,HIGH);
delay(1000);
}
}
}
Project 14：Button-controlled LED
Description：
Usually, a complete open loop control is made of external information input，controller and actuator.
The external information is input into controller which can analyze the input data and send to control signals to make actuator to react.
A button-controlled LED is decided by an open loop control. Next, we will make a desk lamp with a button, an LED and RPi. LED is on when button is pressed, on the contrary, it will be off.
Experiment Components：
|
|
|
|
|
|---|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
LED - Red *1 |
|
|
|
|
|
220Ω Resistor*1 |
Jumper Wires |
10KΩ Resistor*1 |
Button Switch *1 |
Schematic Diagram：
Eliminate Button Shaking
The LED status won’t jump into new state immediately when button is pressed. There will be a short continuous shaking before into new status, which is similar with release status.
Therefore, there will be many a presses and release actions. The shaking will misleads the high speed movement of MCU, causing wrong judgement. That requires that we need to judge the button’ status frequently.
The button means being pressed when its status is stable.
Run Example Code：
Input the following commands and press “Enter”:
cd /home/pi/C_code/lesson14_Button_controlled_LED
gcc Button_controlled_LED.c -o Button_controlled_LED -lwiringPi
sudo ./Button_controlled_LED
Test Results：
Press button, LED turns on, press again, LED is off.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
##include <wiringPi.h>
##include <stdio.h>
##define btnPin 1 // button Pin BCM GPIO 18
##define ledPin 2 // LED pin BCM GPIO 27
int main()
{
wiringPiSetup();
int val; //Button variables
int count = 0; //Record the number of button presses
int flag = 0; //Odd even variable
pinMode(btnPin,INPUT);
pinMode(ledPin,OUTPUT);
digitalWrite(ledPin,LOW); //turn off led
while(1)
{
val=digitalRead(btnPin); //Receive button value
if(val == 0)
{
delay(10);
val=digitalRead(btnPin); //Receive button value
if(val == 1)
{
count = count + 1;
printf("count = %d",count);
}
}
flag = count % 2; //Remainder 2 ,Even is 0, odd is 1
if(flag == 1)
digitalWrite(ledPin,HIGH); //turn on led
else
digitalWrite(ledPin,LOW); //turn off led
}
}
Project 15：Responder
Description：
A responder is someone who answers a question or who acts quickly in response to some event. In this lesson, we will show you how to make a responder and introduce its working principle.
Experiment Components：
|
|
|
|
|
|
|---|---|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
LED - Red *1 |
LED - Green*1 |
|
|
|
|
|
|
LED - Yellow*1 |
220Ω Resistor*3 |
Jumper Wires |
10KΩ Resistor*4 |
Button Switch *4 |
Schematic Diagram：
Design Description：
You could assume a scene that three competitors in knowledge quiz.
Everyone has a responder and an LED. Corresponding LED will turn on if one presses his own responder, however, others’ won’t be on. What’s more, a questioner has a button to control their LEDs. After a round of game, LEDs are off, the quiz restarts.
Run Example Code：
Input the following commands and press “Enter”:
cd /home/pi/C_code/lesson15_Responder
gcc Responder.c -o Responder -lwiringPi
sudo ./Responder
Test Results：
The corresponding LED will turn on if a competitor press his own responder, but others’ are off. The questioner press a button to turn off their LEDs and restart a new round quiz.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
##include <wiringPi.h>
//define the pin
##define redled 25 //BCM GPIO 26
##define yellowled 24 //BCM GPIO 19
##define blueled 23 //BCM GPIO 13
##define redpin 4 //BCM GPIO 23
##define yellowpin 5 //BCM GPIO 24
##define bluepin 6 //BCM GPIO 25
##define restpin 1 //BCM GPIO 18
int red;
int yellow;
int blue;
void clear_led()// all LED off
{
digitalWrite(redled,LOW);
digitalWrite(blueled,LOW);
digitalWrite(yellowled,LOW);
}
void RED_YES()// execute the code until red light is on; end cycle when reset button is pressed
{
while(digitalRead(restpin)==1)
{
digitalWrite(redled,HIGH);
digitalWrite(blueled,LOW);
digitalWrite(yellowled,LOW);
}
clear_led();
}
void YELLOW_YES()// execute the code until yellow light is on; end cycle when reset button is pressed
{
while(digitalRead(restpin)==1)
{
digitalWrite(redled,LOW);
digitalWrite(blueled,LOW);
digitalWrite(yellowled,HIGH);
}
clear_led();
}
void BLUE_YES()// execute the code until green light is on; end cycle when reset button is pressed
{
while(digitalRead(restpin)==1)
{
digitalWrite(redled,LOW);
digitalWrite(blueled,HIGH);
digitalWrite(yellowled,LOW);
}
clear_led();
}
int main()
{
wiringPiSetup();
pinMode(redled,OUTPUT);
pinMode(yellowled,OUTPUT);
pinMode(blueled,OUTPUT);
pinMode(redpin,INPUT);
pinMode(yellowpin,INPUT);
pinMode(bluepin,INPUT);
while(1)
{
//digital read button
red=digitalRead(redpin);
yellow=digitalRead(yellowpin);
blue=digitalRead(bluepin);
if(red==LOW) //red is pressed
{
RED_YES();
}
if(yellow==LOW) //yellow is pressed
{
YELLOW_YES();
}
if(blue==LOW) //blue is pressed
{
BLUE_YES();
}
}
}
Project 16：PIR Motion Sensor
Description：
In this lesson, we will learn about PIR motion sensor.
Experiment Components：
|
|
|
|
|
|---|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
LED - Red *1 |
|
|
|
||
220Ω Resistor*1 |
PIR Motion Sensor*1 |
Jumper Wires |
Component Knowledge：
PIR Motion Sensor：
The principle of human infrared sensor is that when certain crystals, such as lithium tantalate and triglyceride sulfate, are heated, the two ends of the crystal will generate an equal number of charges, with opposite signs, which can be converted into voltage output by an amplifier.
Human body will emit IR ray, although weak but can be detected. Sensor will output high level(1) when human being is detected by sensor, otherwise, it will output low level o.
Note: Nothing but moving person can be detected, with the detection distance is up to 3m.
Schematic Diagram：
Run Example Code：
Input the following commands and press “Enter”:
cd /home/pi/C_code/lesson16_PIR_led
gcc PIR_led.c -o PIR_led -lwiringPi
sudo ./PIR_led
Test Results：
LED will turn on and terminal prints somebody if PIR motion sensor detects people; if not, LED will be off and terminal will print nobody.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
##include <wiringPi.h>
##include <pcf8591.h>
##include <stdio.h>
##define PIR_pin 1 //PIR pin BCM GPIO 18
##define led_pin 21 //LED pin BCM GPIO 5
int main(void)
{
int val = 0;
wiringPiSetup();
pinMode(PIR_pin,INPUT);
pinMode(led_pin,OUTPUT);
while(1)
{
val=digitalRead(PIR_pin);
if(val==1)
{
printf("somebody\n");
digitalWrite(led_pin,HIGH);
}
else
{
printf("nobody\n");
digitalWrite(led_pin,LOW);
}
}
}
Project 17：Fire Alarm
Description：
A flame detector is a sensor designed to detect and respond to the presence of a flame or fire, allowing flame detection.
Experiment Components：
|
|
|
|
|
|---|---|---|---|---|
Raspberry Mainboard*1 |
GPIO Extension Board*1 |
40 pin Colcorful Jumper Wires*1 |
Breadboard*1 |
Active Buzzer *1 |
|
|
|
||
Flame Sensor *1 |
10KΩ Resistor*1 |
Jumper Wires |
Component Knowledge：
Flame Sensor：
Flame sensor is made based on the principle that infrared ray is highly sensitive to flame. It has an infrared receiving tube specially designed to detect fire, and then convert the flame brightness to fluctuating level signal. The signals are then input into the central processor and be dealt with accordingly.
Flame sensor is used to detect fire source with wavelength in 760nm～1100nm, detection angle is 60°. When its IR waves length is close to 940nm, and its sensitivity is highest.
Notice that keep flame sensor away from fire source to defend its damage for its working temperature is between -25°-85°
Schematic Diagram：
Run Example Code：
Input the following commands and press “Enter”:
cd /home/pi/C_code/lesson17_Flame_Sensor
gcc Flame_Sensor.c -o Flame_Sensor -lwiringPi
sudo ./Flame_Sensor
Test Results：
Buzzer will alarm when detecting fire, otherwise, it will stop emitting sound.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
##include <wiringPi.h>
##include <stdio.h>
##define flamePin 1 //BCM GPIO 18
##define buzPin 2 //define buzzer pin BCM GPIO 27
int main()
{
wiringPiSetup();
char val;
{
pinMode(flamePin,INPUT);
pinMode(buzPin,OUTPUT);
}
while(1)
{
val=digitalRead(flamePin);
printf("val = %d\n",val);
if(val==1) //When flame is detected
digitalWrite(buzPin,HIGH); //Buzzer turn on
else
digitalWrite(buzPin,LOW); //Buzzer turn off
}
}
Project 18：Electronic Hourglass
Description：
An hourglass (or sandglass, sand timer, sand clock or egg timer) is a device used to measure the passage of time. It comprises two glass bulbs connected vertically by a narrow neck that allows a regulated flow of a substance (historically sand) from the upper bulb to the lower one. Typically the upper and lower bulbs are symmetric so that the hourglass will measure the same duration regardless of orientation. The specific duration of time a given hourglass measures is determined by factors including the quantity and coarseness of the particulate matter, the bulb size, and the neck width.
Experiment Components：
|
|
|
|
|
|---|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
LED - Red *2 |
|
|
|
|
|
220Ω Resistor*2 |
Ball Tilt Sensor*1 |
10KΩ Resistor*1 |
Jumper Wires |
Component Knowledge：
Ball Tilt Sensor：
Tilt sensors (tilt ball switch) allow you to detect orientation or inclination. They are small, inexpensive, low-power and easy-to-use. If used properly, they will not wear out.
The tilt-switch twig is the equivalent of a button, and is used as a digital input. Inside the tilt switch is a ball that make contact with the pins when the case is upright. Tilt the case over and the balls don’t touch, thus not making a connection. When the switch is level it is open, and when tilted, the switch closes.
It can be used for orientation detection, alarm device or others.
Here is the principle of tilt sensor to illustrate how it works:
Schematic Diagram：
Run Example Code：
Input the following commands and press “Enter”:
cd /home/pi/C_code/lesson18_Ball_Tilt_Sensor
gcc Ball_Tilt_Sensor.c -o Ball_Tilt_Sensor -lwiringPi
sudo ./Ball_Tilt_Sensor
Test Results：
Led1 gradually brightens and led2 gradually darkens when place electronic hourglass, however, as you make it upside down, led1 gradually darkens, led2 gets bright.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
##include <stdio.h>
##include <stdlib.h>
##include <stdint.h>
##include <wiringPi.h>
##include <softPwm.h>
//define led pin
##define LED1 0 //BCM GPIO 17
##define LED2 2 //BCM GPIO 27
//define Ball Tilt Sensor Pin
##define tiltPin 1 //BCM GPIO 18
int main(void){
int val;
int val1 = 50; //Initial value of LED brightness
int val2 = 50;
if (wiringPiSetup() == -1)
{
printf("Setup GPIO error!\n");
return -1;
}
softPwmCreate(LED1, 0, 100); //Define the pin as PWM output
softPwmCreate(LED2, 0, 100);
while (1)
{
val=digitalRead(tiltPin); //Read the value of the tilt sensor
if(val==0) //upright
{
val1++; //The value of LED1 increases
val2--; //Led2 value reduced
if(val1>=100) //The size of the limit
{
val1 = 100;
}
if(val2<=0) //The size of the limit
{
val2 = 0;
}
softPwmWrite(LED1, val1); //The value after PWM output changes
softPwmWrite(LED2, val2);
delay(50); //Delay, adjust the speed
}
else
{
val1--;
val2++;
if(val1<=0)
{
val1 = 0;
}
if(val2>=100)
{
val2 = 100;
}
softPwmWrite(LED1, val1);
softPwmWrite(LED2, val2);
delay(50);
}
}
return 0;
}
Project 19：Stepless Dimming
Description：
A stepless dimming control method of a lighting system is applicable to the situations where a light source for a lighting terminal is a fluorescent lamp and/or an LED lamp.
Experiment Components：
|
|
|
|
|
|---|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
Potentiometer*1 |
|
|
|||
Keyestudio PCF8591 A/D Converter Module*1 |
Jumper Wires |
Component Knowledge：
Keyestudio PCF8591 A/D Converter Module：
Raspberry Pi doesn’t come with AD/DA function. It has to be connected AD/DA shield if it is connected to analog sensor. We use pcf8591 AD/DA converter which adopts iic communication. Therefore, the operation steps are shown below:
a. Enter sudo raspi-config and press “Enter” to navigate the configuration page.
b. Enable the I2C function according to the following pictures( press（↑）,（↓）,（←）,（→）on the keyboard and “Enter”k）
You could check more detail about I2C communication agreement in the following link:
https://www.nxp.com/docs/en/user-guide/UM10204.pdf
PCF8591 Pins:
More details about PCF8591 chip, you could look through chip specification folder
From the below figure, PCF8591 has an analog output pin Aout and four analog input pin A0-A3.
Check the address of iic module（PCF8591）of Raspberry Pi, enter command i2cdetect -y 1 and press Enter.
The iic address of PCF8591 is 0x48.
Used to read the address of pin A0~A3.
The address of analog output pin AOUT: 0x40, that is, 64 converting from hexadecimal to decimal.
A0 = 0x40 ####A0 —-> port address
A1 = 0x41
A2 = 0x42
A3 = 0x43
Adjustable Potentiometer
The rotary potentiometer means the change of resistance.
We could convert the resistance’s change into the voltage’s when setting circuit. Then, voltage changes will be output to GPIO port through module signals.
Wiring according to the below figure and rotate clockwise, resistance value reduces.
Schematic Diagram：
Note: PCF8591 module comes with an LED connected to Aout pint .
Run Example Code：
Input the following commands and press “Enter”:
cd /home/pi/C_code/lesson19_PWM_control_LED
gcc PWM_control_LED.c -o PWM_control_LED -lwiringPi
sudo ./PWM_control_LED
Test Results：
Terminal prints the analog value read by adjustable potentiometer. The LED brightness will vary with the the rotary of potentiometer.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
##include <wiringPi.h>
##include <pcf8591.h> //pcf8591 library
##include <stdio.h>
##define Address 0x48 //iic address
##define BASE 64 //DAC write address
##define A0 BASE+0 //A0 analogRead address
##define A1 BASE+1 //A1 analogRead address
##define A2 BASE+2
##define A3 BASE+3
int main(void)
{
unsigned char value;
wiringPiSetup();
pcf8591Setup(BASE,Address); //Initialize the pcf8591
while(1)
{
value=analogRead(A0); //read the ADC value of channel 0
printf("A0:%d\n",value);
analogWrite(BASE,value); //write the DAC value
printf("AOUT:%d\n",value);
delay(100);
}
}
Knowledge：
##define Address 0x48 pcf8591Setup(BASE,Address); |
Icc address of PCF8591 is set to 0x48 |
|---|---|
##define BASE 64 ##define A0 BASE+0 ##define A1 BASE+1 ##define A2 BASE+2 ##define A3 BASE+3 |
pcf8591 analog port Set the address of A0 to 0x40 Set the address of A1 to 0x41 Set the address of A2 to 0x42 Set the address of A3 to 0x43 |
Project 20：Photoresistor
Description：
Photo resistor (Photovaristor) is a resistor whose resistance varies according to different incident light strength. It’s made based on the photoelectric effect of semiconductor. In this lesson, let’s explain how it works.
Experiment Components：
|
|
|
|
|
|---|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
LED - Red *1 |
|
|
|
|
|
220Ω Resistor*1 |
Photo Resistor*1 |
10KΩ Resistor*1 |
Keyestudio PCF8591 A/D Converter Module*1 |
Jumper Wires |
Component Knowledge：
Photoresistor：
Photo resistor (Photovaristor) is a resistor whose resistance varies according to different incident light strength. It’s made based on the photoelectric effect of semiconductor. If the incident light is intense, its resistance reduces; if the incident light is weak, the resistance increases.
If incident light on a photoresistor exceeds a certain frequency, photons absorbed by the semiconductor give bound electrons enough energy to jump into the conduction band. The resulting free electrons (and their hole partners) conduct electricity, thereby lowering resistance.
Schematic Diagram：
Run Example Code：
Note: in the experiment, I2C communication is used. We need to check the iic address first( enter command：i2cdetect -y 1 and press “Enter”. If failed, check the wiring is correct or not. If correct, you need to enable I2C communication function of Raspberry Pi, project 19 is for your reference.
After enabling I2C communication, input the following commands and press “Enter”:
cd /home/pi/C_code/lesson20_Photo_resistor
gcc Photo_resistor.c -o Photo_resistor -lwiringPi
sudo ./Photo_resistor
Test Results：
Terminal prints the value tested by photoresistor. LED will turn on if the ambient environment is dim, otherwise, LED will be off.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
##include <wiringPi.h>
##include <pcf8591.h>
##include <stdio.h>
##define Address 0x48
##define BASE 64
##define A0 BASE+0
##define A1 BASE+1
##define A2 BASE+2
##define A3 BASE+3
##define ledPin 21 //led pin BCM GPIO 5
int main(void)
{
unsigned char value;
wiringPiSetup();
pcf8591Setup(BASE,Address);
pinMode(ledPin,OUTPUT);
while(1)
{
value=analogRead(A0);
printf("A0:%d\n",value);
delay(100);
if(value>100)
digitalWrite(ledPin,HIGH);
else
digitalWrite(ledPin,LOW);
}
}
Project 21：Sound-activated Light
Description：
You might find the lights automatically on when you pass them, nevertheless, they will be off if the surrounding is quiet. Do you know why?
Actually, it is sound sensor that controls them on and off.
Experiment Components:
|
|
|
|
|
|---|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
LED - Red *1 |
|
|
|
|
|
220Ω Resistor*1 |
Sound Sensor*1 |
Jumper Wires |
Keyestudio PCF8591 A/D Converter Module*1 |
Component Knowledge：
Sound Sensor：
A sound sensor is defined as a module that detects sound waves through its intensity and converting it to electrical signals.
The sound sensor has a built-in capacitive electret microphone which is highly sensitive to sound. Sound waves cause the thin film of the electret to vibrate and then the capacitance changes, thus producing the corresponding changed voltage. Since the voltage change is extremely weak, it needs to be amplified.
So it is converted into a voltage ranging from 0 to 5V, which is received by data acquisition unit after A/D adapter conversion and then sent to an MCU.
The module can be applied to noise monitoring in traffic artery, and detection of noises within the boundary of industrial enterprises, factories, and construction sites, detection of noises in urban regions, and noise detection and assessment of living surroundings.
Schematic and Connection Diagram：
Run Example Code：
Note: in the experiment, I2C communication is used. We need to check the iic address first( enter command：i2cdetect -y 1 and press“Enter”. If failed, check the wiring is correct or not. If correct, you need to enable I2C communication function of Raspberry Pi, project 19 is for your reference.
After enabling the I2C communication，input the following commands and press “Enter”:
cd /home/pi/C_code/lesson21_sound
gcc Sound_led.c -o Sound_led -lwiringPi
sudo ./Sound_led
Test Results：
When you clap your hands suddenly, LED lights up and clap again, LED is off.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
##include <wiringPi.h>
##include <pcf8591.h>
##include <stdio.h>
##define Address 0x48
##define BASE 64
##define A0 BASE+0
##define A1 BASE+1
##define A2 BASE+2
##define A3 BASE+3
##define ledPin 21 //led pin //BCM GPIO 5
int count = 0;
int flag = 0;
int main(void)
{
unsigned char value;
wiringPiSetup();
pcf8591Setup(BASE,Address);
pinMode(ledPin,OUTPUT);
while(1)
{
value=analogRead(A0); //Read the value of the sound sensor
printf("A0:%d\n",value);
delay(100);
if(value>80)
{
count = count + 1;
flag = count % 2;
}
if(flag == 1)
{
digitalWrite(ledPin,HIGH);
}
else
{
digitalWrite(ledPin,LOW);
}
}
}
Project 22：LCD1602 & MQ-2 Gas Leakage Alarm
Description：
Some households have access to gas, which is composed of CO, CO2, N2, H2 and CH4. CO is one of toxic gases. People will be in danger if absorbing too much CO. However, we could tackle with this problem over a gas leakage alarm.
Gas MQ-2 leakage alarm detects the presence of a combustible or toxic gas and react by displaying a reading, setting off an audible or visual alarm.
Experiment Components：
|
|
|
|
|
|
|---|---|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Jumper Wires*1 |
Breadboard*1 |
Potentiometer*1 |
Active Buzzer *1 |
|
|
|
|
|
|
LCD1602 display*1 |
Gas MQ-2 Sensor * 1 |
PCF8591 A/D Module*1 |
Jumper Wires |
M-F Dupont Line |
Component Knowledge：
MQ-2 gas sensor adopts the material sensitive to gas——SnO2 with low electricity conductivity. When beset with combustible gas, its electricity conductivity varies with the of the concentration of flammable gas, however, the simple circuit could convert the change of electricity conductivity into the output signals of the concentration of gas sensor.
MQ-2 gas sensor is a multi-purpose and cost-effective. It can detect the concentration of flammable gas and smoke in the range of 300~10000ppm.Meanwhile, it has high sensitivity to natural gas, liquefied petroleum gas and other smoke, especially to alkanes smoke.
LCD1602 LED Display：
It could show the characters or numbers in 16 rows and 2 columns
1602 LCD Pins:
Pin 1 |
GND |
|---|---|
Pin 2 |
VCC is connected to positive of 5V |
Pin 3 |
V0 is the contrast adjustment terminal of LCD. The contrast is the weakest when the positive power is connected, and the contrast is the highest when the power is grounded (for high contrast causing double image a 10K potentiometer can help adjust contrast during use) |
Pin 4 |
RS is register selection, select data register when high level 1 and choose command register when low level 0 |
Pin 5 |
RW is reading and writing signal line. Reading operation actives if high level(1)，writing operation actives ig low level(0) |
Pin 6 |
E(EN) is enable end, read information when high level(1), execute the command when low level(0) |
Pin 7~14 |
D0～D7 are 8-bit two-way data ends |
Pin 15 |
Positive of backlight |
Pin 16 |
Negative of backlight |
LCD1602 usually uses eight data cable to provide the data of Data0~Data7, however, it supports“4Bits”mode which is so called four data cables so as to save GPIO ports
Schematic Diagram：
Run Example Code：
Note: in the experiment, I2C communication is used. We need to check the iic address first( enter command：i2cdetect -y 1 and press“Enter”. If failed, check the wiring is correct or not. If correct, you need to enable I2C communication function of Raspberry Pi, project 19 is for your reference.
After enabling the I2C communication，Input the following commands and press “Enter”:
cd /home/pi/C_code/lesson22_LCD1602_MQ2
gcc 1602_MQ2.c -o 1602_MQ2 -lwiringPiDev -lwiringPi
sudo ./1602_MQ2
Test Results：
Buzzer alarms when detecting the poisonous gas.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
##include <stdio.h>
##include <stdlib.h>
##include <string.h>
##include <wiringPi.h>
##include <pcf8591.h>
##include <lcd.h>
##define Address 0x48
##define BASE 64
##define A0 BASE+0
##define A1 BASE+1
##define A2 BASE+2
##define A3 BASE+3
##define buzPin 28 //buzzer pin BCM GPIO 20
void change(int num,char *src) //This function changes 1234 to 4321 of the string
{
char temp = '\0';
int m = 0;
int i = 0;
while(num != 0)
{
m = num%10;
temp = m+'0';
src[i] = temp;
i++;
num = num/10;
}
src[i] = '\0';
}
int main(void)
{
unsigned char dat;
wiringPiSetup();
pcf8591Setup(BASE,Address);
int fd;
int i;
if (wiringPiSetup() == -1){
exit(1);
}
fd = lcdInit(2,16,4, 24,23, 3,2,0,7,0,0,0,0); //set LCD pin
printf("%d", fd);
if (fd == -1){
printf("lcdInit 1 failed\n") ;
return 1;
}
lcdClear(fd);
{
pinMode(buzPin,OUTPUT);
}
while(1){
dat=analogRead(A0);
if(dat>60)
digitalWrite(buzPin,HIGH);
else
digitalWrite(buzPin,LOW);
int i = 0;
int len = 0;
char temp; //Define an intermediate variable
char *src = (char*)malloc(sizeof(char)*100);
change(dat,src);
len = strlen(src);
for(i = 0;i < len/2;i++) //Output the string in reverse order
{
temp = src[i];
src[i] = src[len-i-1];
src[len-i-1] = temp;
}
printf("MQ2:%d\n",dat);
lcdPosition(fd, 0, 0);
lcdPuts(fd, "MQ2");
lcdPosition(fd, 0, 1);
lcdPuts(fd, src);
delay(100);
lcdClear(fd);
}
return 0;
}
Project 23：Water Level Monitor
Description：
If you have ever had a water heater explode or ever tried to make submersible electronics, then you know how important it is to detect when water is around. Let’s know more about water level sensor.
Experiment Components:
|
|
|
|
|
|---|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
Active Buzzer *1 |
|
|
|
|
|
Water Level Sensor * 1 |
PCF8591 A/D Converter Module*1 |
Jumper Wires |
M-F Dupont Line |
Component Knowledge：
Water Level Sensor：
Our water sensor is easy- to-use, portable and cost-effective, designed to identify and detect water level and water drop.
This sensor measures the volume of water drop and water quantity through an array of traces of exposed parallel wires.
It could convert water content to analog signals, and output analog value could be used by function of application. It has the features of low consumption as well.
Schematic and Connection Diagram：
Run Example Code：
Note: in the experiment, I2C communication is used. We need to check the iic address first( enter command：i2cdetect -y 1 and press“Enter”. If failed, check the wiring is correct or not. If correct, you need to enable I2C communication function of Raspberry Pi, project 19 is for your reference.
After enabling the I2C communication，input the following commands and press “Enter”:
cd /home/pi/C_code/lesson23_water
gcc water.c -o water -lwiringPi
sudo ./water
Test Results：
Buzzer makes a sound when water covering the exposed detection part.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
##include <wiringPi.h>
##include <pcf8591.h>
##include <stdio.h>
##define Address 0x48
##define BASE 64
##define A0 BASE+0
##define A1 BASE+1
##define A2 BASE+2
##define A3 BASE+3
##define buzPin 1 //buzzer pin BCM GPIO 18
int main(void)
{
unsigned char value;
wiringPiSetup();
pcf8591Setup(BASE,Address);
pinMode(buzPin,OUTPUT);
while(1)
{
value=analogRead(A0); //Read the value of the water sensor
printf("A0:%d\n",value);
delay(100);
if(value>30)
{
digitalWrite(buzPin,HIGH);
}
else
{
digitalWrite(buzPin,LOW);
}
}
}
Project 24：5V Relay + Water Pump
Description：
From a safety perspective, we specially designed this relay module with NO (normally open) and NC (normally closed) terminals. In this lesson, we will learn a special and easy-to-use switch, which is the relay module. Use the relay to start the motor.
In daily life, the electronic device is driven by 220V AC and controlled by switch. People will be in danger once the electricity leakage happens, connecting switch to 220V AC directly.
Therefore, we design a relay module with NO and NC ends. Let’s get started.
Experiment Components：
|
|
|
|
|
|
|---|---|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40pin Colorful Jumper Wires*1 |
Breadboard*1 |
Relay Module*1 |
Water Pipe*1 |
|
|
|
|
|
|
M-F Dupont Line |
220Ω Resistor*1 |
Screwdriver*1 |
Jumper Wires |
Water Pump*1 |
Component Knowledge：
Relay: It is an “automatic switch” that uses a small current to control the operation of a large current.
Control input voltage: 5V
Rated load: 5A 250VAC (NO/NC) 5A 24VDC (NO/NC)
Rated load: You can use the 5V voltage of the Raspberry Pi to control a device with a DC voltage of 24V or an AC voltage of 250V.
Water Pump
Working voltage: DC3-5V,
Working current: 100-200mA,
Head: 0.3-0.8 meters,
Flow rate: 1.2-1.6L/min,
Weight: 28 grams
Schematic Diagram：
Run Example Code：
Input the following commands and press “Enter”:
cd /home/pi/C_code/lesson24_relay
gcc relay.c -o relay -lwiringPi
sudo ./relay
Test Results：
Water pump activates when the indication on relay module turns on.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
##include <wiringPi.h>
##include <stdio.h>
##define relayPin 1 //BCM GPIO 18
int main()
{
wiringPiSetup();
pinMode(relayPin,OUTPUT);
while(1)
{
digitalWrite(relayPin,HIGH);
printf("turn on\n");
delay(5000);
digitalWrite(relayPin,LOW);
printf("turn off\n");
delay(1000);
}
}
Project 25：Flower-watering Device
Description：
The household plants are popular in many a communities. They will die if you forget to water them, how about making an automatic watering device?
Experiment Components：
|
|
|
|
|
|---|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
Relay Module*1 |
|
|
|
|
|
Water Pump*1 |
Soil Humidity Sensor*1 |
Keyestudio PCF8591 A/D Converter Module*1 |
220Ω Resistor*1 |
Water Pipe*1 |
|
|
|
||
M-F Dupont Line |
Jumper Wires |
Screwdriver*1 |
Component Knowledge：
Soil Humidity Sensor：
This is a simple soil humidity sensor aims to detect the soil humidity. If the soil is in lack of water, the analog value output by the sensor will decrease; otherwise, it will increase. If you use this sensor to make an automatic watering device, it can detect whether your botany is thirsty to prevent it from withering when you go out.
Using the sensor with controller makes your plant more comfortable and your garden smarter. The soil humidity sensor module is not as complicated as you might think, and if you need to detect the soil in your project, it will be your best choice.
Schematic Diagram：
Run Example Code：
Note: in the experiment, I2C communication is used. We need to check the iic address first( enter command：i2cdetect -y 1 and press“Enter”. If failed, check the wiring is correct or not. If correct, you need to enable I2C communication function of Raspberry Pi, project 19 is for your reference.
After enabling the I2C communication，input the following commands and press “Enter”:
cd /home/pi/C_code/lesson25_soil
gcc soil.c -o soil -lwiringPi
sudo ./soil
Test Results：
Water pump starts running when soil humidity sensor detects the drought of soil.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
##include <wiringPi.h>
##include <pcf8591.h>
##include <stdio.h>
##define Address 0x48 //address ---> device address
##define BASE 64 //DA converter command
##define A0 BASE+0 //A0 ----> port address
##define A1 BASE+1
##define A2 BASE+2
##define A3 BASE+3
##define relayPin 1 //BCM GPIO 18
int main(void)
{
unsigned char value;
wiringPiSetup();
pcf8591Setup(BASE,Address); //which port of the device you want to access
pinMode(relayPin,OUTPUT);
while(1)
{
value=analogRead(A0);
printf("A0:%d\n",value);
delay(100);
if(value<30)
digitalWrite(relayPin,HIGH);
else
digitalWrite(relayPin,LOW);
}
}
Project 26：Servo
Description：
Servo is applied widely, especially for robot like human robots and moving robots. In this lesson, we will learn how it works.
Experiment Components：
|
|
|
|
|
|
|---|---|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
Servo Motor*1 |
Jumper Wires |
Component Knowledge：
Servo:
A location(angle) driver which can rotate a certain angle with high accuracy. It has three external wires which are brown, red and orange,. Brown one is grounded, red one is positive pole of power and orange one is signal wire.
The rotation angle of servo motor is controlled by regulating the duty cycle of PWM (Pulse-Width Modulation) signal. The standard cycle of PWM signal is 20ms(50Hz). Theoretically, the width is distributed between 1ms-2ms, but in fact, it’s between 0.5ms-2.5ms. The width corresponds the rotation angle from 0° to 180°. But note that for different brand motor, the same signal may have different rotation angle.
Schematic Diagram：
Run Example Code：
Input the following commands and press “Enter”:
cd /home/pi/C_code/lesson26_Servo
gcc Servo.c -o Servo -lwiringPi
sudo ./Servo
Test Results：
Servo rotates in the range of 0°-180°.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
##include <wiringPi.h>
##define serPin 1 //servo pin BCM GPIO 18
int main()
{
wiringPiSetup();
pinMode(serPin,OUTPUT);
int i;
for(;;)
{
for(i=0;i<50;i++)
{
digitalWrite(serPin,HIGH);
delayMicroseconds(500); //Pulse width 0.5ms, Angle 0
digitalWrite(serPin,LOW);
delay(20-0.5); //Cycle 20 ms
}
delay(1000);
for(i=0;i<50;i++)
{
digitalWrite(serPin,HIGH);
delayMicroseconds(2500);
digitalWrite(serPin,LOW);
delay(20-2.5);
}
delay(1000);
}
return 0;
}
Project 27：L293D Driver Motor
Description：
In generally, we use a DC motor to make smart car. What should we do if we want to control the rotation speed and direction? Here, we need an L293D driver motor.
Experiment Components:
|
|
|
|
|
|---|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful jumper Wires*1 |
Breadboard*1 |
Jumper Wires |
|
|
|
||
L293D Chip*1 |
Fan |
Motor*1 |
Component Knowledge:
L293D Chip:
It is a DC current DC IC which is applied to drive DC motor and stepper motor. In addition, it has 16 pins driving two-way DC motor at same time.
Input voltage range: 4.5 V ~ 36 V
Output current: MAX 600mA, can drive inductive loaded, especially its input end can be connected to MCU directly, controlled by MCU easily.
The two-channel motor can be driven and rotate clockwise and anticlockwise when changing the high and low level on input port.
## |
Pin Name |
Description |
|---|---|---|
1 |
Enable1 |
Enable pin input 1(2) and Input 2(7) |
2 |
In1 |
Control output1 and controlled by digital circuit |
3 |
Out1 |
Connect one end of motor1 |
4 |
0V |
Connected to 0V of circuit. |
5 |
0V |
Connected to 0V of circuit. |
6 |
Out2 |
Connect the other end of motor1 |
7 |
In2 |
Control output2 and controlled by digital circuit |
8 |
+V motor |
Connect to 4.5V-36V) of motor |
9 |
Enable2 |
Enable pin input 3(10) and 4(15) |
10 |
In3 |
Control output pin 3 |
11 |
Out3 |
Connect one end of motor 2 |
12 |
0V |
Connected to 0V of circuit. |
13 |
0V |
Connected to 0V of circuit. |
14 |
Out4 |
Connect the other end of motor 2 |
15 |
In4 |
Control output 4 and controlled by digital circuit |
16 |
+V |
Connect to + 5V to enable IC function |
Schematic Diagram：
Run Example Code：
Input the following commands and press “Enter”:
cd /home/pi/C_code/lesson27_L293D
gcc L293D.c -o L293D -lwiringPi
sudo ./L293D
Test Results：
Motor rotates clockwise for 3s, stops for 2s, anticlockwise for 3s and stops for 2 s.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
##include <stdio.h>
##include <stdlib.h>
##include <stdint.h>
##include <wiringPi.h>
##include <softPwm.h>
//define L293D pin
##define INA1 0 //BCM GPIO 17
##define INA2 2 //BCM GPIO 27
##define ENA 3 //BCM GPIO 22
void forward()
{
digitalWrite(INA1,HIGH);
digitalWrite(INA2,LOW);
softPwmWrite(ENA, 80); //pwm : 0~100
}
void reverse()
{
digitalWrite(INA1,LOW);
digitalWrite(INA2,HIGH);
softPwmWrite(ENA, 80); //pwm : 0~100
}
void stop()
{
digitalWrite(INA1,LOW);
digitalWrite(INA2,LOW);
softPwmWrite(ENA, 0);
}
int main(void)
{
wiringPiSetup();
pinMode(INA1,OUTPUT);
pinMode(INA2,OUTPUT);
softPwmCreate(ENA, 0, 100);
while(1)
{
forward();
delay(3000);
stop();
delay(2000);
reverse();
delay(3000);
stop();
delay(2000);
}
return 0;
}
Project 28：Ultrasonic Sensor
Description：
An ultrasonic sensor is an electronic device that measures the distance of a target object by emitting ultrasonic sound waves, and converts the reflected sound into an electrical signal.
Experiment Components：
|
|
|
|
|
|
|---|---|---|---|---|---|
Raspberry Pi*1 |
GPIO Extension Board*1 |
40 pin Colorful Jumper Wires*1 |
Breadboard*1 |
HC-SR04 Ultrasonic Sensor*1 |
Jumper Wires |
Component Knowledge：
The ultrasonic module will emit the ultrasonic waves after trigger signal. When the ultrasonic waves encounter the object and are reflected back, the module outputs an echo signal, so it can determine the distance of object from the time difference between trigger signal and echo signal.
The t is the time that emitting signal meets obstacle and returns and the propagation speed of sound in the air is about 343m/s, therefore, distance = speed * time, because the ultrasonic wave emits and comes back, which is 2 times of distance, so it needs to be divided by 2, the distance measured by ultrasonic wave = (speed * time)/2
Use method and timing chart of ultrasonic module: Setting the delay time of Trig pin of SR04 to 10μs at least, which can trigger it to detect distance.
2. After triggering, the module will automatically send eight 40KHz ultrasonic pulses and detect whether there is a signal return. This step will be completed automatically by the module.
3. If the signal returns, the Echo pin will output a high level, and the duration of the high level is the time from the transmission of the ultrasonic wave to the return.
Schematic Diagram：
Run Example Code：
Input the following commands and press “Enter”:
cd /home/pi/C_code/lesson28_Ultrasonic
gcc Ultrasonic.c -o Ultrasonic -lwiringPi
sudo ./Ultrasonic
Test Results：
Terminal prints the detected distance, unit is cm.
Note: Press Ctrl + C on keyboard and exit code running.
Example Code：
##include <wiringPi.h>
##include <stdio.h>
##include <sys/time.h> //Import the time system header file
//define the pin
##define Trig 4 //BCM GPIO 23
##define Echo 5 //BCM GPIO 24
//set pin mode
void ultraInit(void)
{
pinMode(Echo, INPUT);
pinMode(Trig, OUTPUT);
}
//Write programs based on sequence diagrams
float disMeasure(void)
{
struct timeval tv1; //Create the Timeval structure tv1
struct timeval tv2; //Create the Timeval structure tv2
long start, stop;
float dis;
digitalWrite(Trig, LOW);
delayMicroseconds(2);
digitalWrite(Trig, HIGH);
delayMicroseconds(10);
digitalWrite(Trig, LOW);
while(!(digitalRead(Echo) == 1)); //Wait for the low level received by the Echo pin to pass
gettimeofday(&tv1, NULL); //function gettimeofday, The time it took the system to get here
while(!(digitalRead(Echo) == 0)); //Wait for the high level received by the Echo pin to pass
gettimeofday(&tv2, NULL); //function gettimeofday, The time it took the system to get here
//Tv1.tv_sec is the seconds obtained, tv1.TV_USec is the subtlety obtained
//Calculate the first time
start = tv1.tv_sec * 1000000 + tv1.tv_usec;
//Calculate the second time
stop = tv2.tv_sec * 1000000 + tv2.tv_usec;
//stop - start , the time difference is the high level time acquired by the echo pin
//34000cm/s, speed of sound
//Calculate the distance measured(cm)
dis = (float)(stop - start) / 1000000 * 34000 / 2;
return dis;
}
int main(void)
{
float dis;
if(wiringPiSetup() == -1){ //when initialize wiring failed,print messageto screen
printf("setup wiringPi failed !");
return 1;
}
ultraInit();
while(1){
dis = disMeasure();
printf("distance = %0.2f cm\n",dis);
delay(100);
}
return 0;
}
<sys/time.h> link：
https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/sys_time.h.html