[SOLVED] Using PWM in 16f877A with adc

[arnab913]

Hello,
I am working with the 16f877A,using PWM with ADC. I've writtten a code,but it is not working.....I am cheaking it again & again..but nothing. :-(
The motor works without the ADC value...wheather it is 5 or 0V.
I don't understand why???
Here is the code....

double pwm;
void main() {
   PWM1_Init(1000);              // PWM of 1kHz
  ADCON1=101000010;
  TRISA=0b00000001;
  PORTA=0;
   TRISB=0b00000010;             // portb as output
   PORTB=0;
   PWM1_Start();         // starting PWM
   if (PORTB.f1==1)
    {
 while(1)
  {

    pwm=ADC_Read(0);
   PWM1_Set_Duty(pwm);

            }
   delay_ms(100);
     }
}

Oscilloscope is not also showing PWM! Pls help.....
Here the image

 

[internetuser2k12]

Try this code and see if it works.

double pwm;

void main() {
   PWM1_Init(2000);                     // PWM of 1kHz
   TRISA = 0x01;
   PORTA = 0x00;
   TRISB = 0x02;                  // portb as output
   PORTB = 0x00;
   ADCON1 = 0b101001110;
   CMCON = 0x07;

   PWM1_Start();                        // starting PWM

   while(1) {
      if(PORTB.f1 == 1)
      {
         pwm =  ADC_Read(0);
         PWM1_Set_Duty(pwm);
         delay_ms(100);
      }
   }
}

You are not assigning any value to RB0. How can it control anything?

Check this. http://www.robotroom.com/PWM5.html

 

[arnab913]

Thanx for reply,but it is still not working......not understanding why,is there any problem in the schematic??? :-(

 

[internetuser2k12]

zip and post your shcematic. It is working. Check this code.

double pwm;

void main() {
   PWM1_Init(1000);              // PWM of 1kHz
   TRISA = 0b00000001;
   PORTA = 0x00;
   TRISB = 0b00000010;             // portb as output
   PORTB = 0x00;
   ADCON1 = 0b101001110;
   CMCON = 0x07;

   PWM1_Start();                  // starting PWM
   
   while(1) {
      if(PORTB.F1 == 1)
      {
         pwm =  ADC_Read(0);
         PWM1_Set_Duty(pwm);
         delay_ms(100);
      }
   }
}

Just Connect RC2/CCP1 pin to the transistor.

 

[arnab913]

Thanx to internetuser2k12
Yes!! it worked!!
I made mistake connecting the transistor pin....
But I couldn't understand ---"CMCON = 0x07;"
what it means? and what is the use of the diode across the motor?
Thanx in advance...

 

[internetuser2k12]

CMCON = 0x07 means the Comparator is disabled. Diode accross the motor is to bypass back emf induced while switching on and off the motor.

 

[arnab913]

But,where i've declared RC2/CCP1 pin as output pin in the code???

 

[internetuser2k12]

RC2/CCP1 pin is internal to PWM. It works internally with the PWM library.