Raspberry pi Software Driven PWM using C++

Question

I am using software driven PWM which is capable of outputting a PWM signal on any GPIO pins. Following Gordon's page.

I am trying to run 2 DC motors

I am using GPIO pin 18 also knowing that it is used for Hardware Driven PWM.I am able to compile program with no errors but after executing the program i dint recieve any output(Motors are not working)

pi@raspberrypi:~ $ g++ wipi.cpp -lwiringPi -lpthread -o wipi pi@raspberrypi:~ $ sudo ./wipi

Apologies My understanding in implementing PWM (using C++) is limited. Any hints and suggestion would be great help. Thank you !

#include<iostream>
#include<wiringPi.h>
#include <softPwm.h>

using namespace std;

#define  MotorPin1 17
#define  MotorPin2 18
#define  MotorEnableDC1 4

#define MotorPin3 27
#define MotorPin4 22
#define MotorEnableDC2 23


 int main(void)
 {

 if(wiringPiSetupGpio()==-1)
{
    cout<<"Setup wiring pi failed";
    return 1;
}


pinMode(MotorPin1,OUTPUT);
pinMode(MotorPin2,OUTPUT);
pinMode(MotorEnableDC1,OUTPUT);

pinMode(MotorPin3,OUTPUT);
pinMode(MotorPin4,OUTPUT);
pinMode(MotorEnableDC2,OUTPUT);

softPwmCreate(MotorEnableDC1,0,50);
softPwmCreate(MotorEnableDC2,0,50);

while(1)
{

    softPwmWrite(MotorEnableDC1,HIGH);
    digitalWrite(MotorPin1,HIGH);
    digitalWrite(MotorPin2,LOW);
    delay(5000);
    softPwmWrite(MotorEnableDC1,LOW);

    softPwmWrite(MotorEnableDC2,HIGH);
    digitalWrite(MotorPin3,LOW);
    digitalWrite(MotorPin4,HIGH);
    delay(5000);
    softPwmWrite(MotorEnableDC2,LOW);
}
return 0;
}

Answer 1

Assuming that you have wired up correctly the most obvious error is the softPwmWrite() parameter of HIGH which I assume will be 1.

You need to give a larger value, try something like 100000 (I don't know what the legal range is but I believe it is clipped to the maximum value).

Given that you use softPwmCreate(MotorEnableDC1,0,50) I would try softPwmWrite(MotorEnableDC1, 50).

The relevant prototypes are

extern int  softPwmCreate (int pin, int value, int range) ;
extern void softPwmWrite  (int pin, int value) ;
extern void softPwmStop   (int pin) ;

Answer 2

Try this for a half-duty cycle (half speed)

softPwmWrite(MotorEnableDC1,25);
softPwmWrite(MotorEnableDC2,25);

Answer 3

You have to use the wiring pi / gpio pin numbers not the physical ones it should be 0 1 2 for dc1 and 3 4 5 but use the wiring pi pins (look at the pic you will understand)