Freenove Ultimate Starter Kit

163
Chapter 15 Servo
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Code
In this project, we make the servo rotate from 0 degrees to 180 degrees, and then from 180 degrees to 0
degrees.
C Code 15.1.1 Sweep
First observe the project result, and then analyze the code.
1. Use cd command to enter 15.1.1_Sweep directory of C code.
cd ~/Freenove_Ultimate_Starter_Kit_for_Raspberry_Pi/Code/C_Code/15.1.1_Sweep
2. Use following command to compile "Sweep.c" and generate executable file "Sweep".
gcc Sweep.c -o Sweep -lwiringPi
3. Run the generated file "Sweep".
sudo ./Sweep
After the program is executed, the servo will rotate from 0 degrees to 180 degrees, and then from 180 degrees
to 0 degrees, circularly.
The following is the program code:
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#include <wiringPi.h>
#include <softPwm.h>
#include <stdio.h>
#define OFFSET_MS 3 //Define the unit of servo pulse offset: 0.1ms
#define SERVO_MIN_MS 5+OFFSET_MS //define the pulse duration for minimum angle of
servo
#define SERVO_MAX_MS 25+OFFSET_MS //define the pulse duration for maximum angle of
servo
#define servoPin 1 //define the GPIO number connected to servo
long map(long value,long fromLow,long fromHigh,long toLow,long toHigh){
return (toHigh-toLow)*(value-fromLow) / (fromHigh-fromLow) + toLow;
}
void servoInit(int pin){ //initialization function for servo PWM pin
softPwmCreate(pin, 0, 200);
}
void servoWrite(int pin, int angle){ //Specif a certain rotation angle (0-180) for the
servo
if(angle > 180)
angle = 180;
if(angle < 0)
angle = 0;
softPwmWrite(pin,map(angle,0,180,SERVO_MIN_MS,SERVO_MAX_MS));
}
void servoWriteMS(int pin, int ms){ //specific the unit for pulse(5-25ms) with
specific duration output by servo pin: 0.1ms
if(ms > SERVO_MAX_MS)
ms = SERVO_MAX_MS;