Pregunta

I've been trying to use the PWM module on a PIC16F877 MCU but all I get is a flat low level on both CCP1/CCP2 pins.

The code configuring and starting the PWM module is the following.

// Configure PWM
// Timer 2 (PWM timebase)
TMR2 = 0;    //Clear timer
TOUTPS0 = 0;
TOUTPS1 = 0;
TOUTPS2 = 0;
TOUTPS3 = 1; //Postscaler -> 8 (previously set to 0)
T2CKPS0 = 0;
T2CKPS1 = 1; //Prescaler -> 16
TMR2IF  = 0;
TMR2IE  = 1; //Interrupt
PR2 = 233;   //~2.5ms

//PWM1 config
CCPR1L = 0x0F;
CCP1X = 0;
CCP1Y = 0; //PWM1 duty cycle 
TRISB2 = 0;  //CCP1 pin is output (Error is here, see below)
TMR2ON = 1;  //Enable timer 
CCP1CON = 0x0c; //CPP1 is a PWM

Any code (PICC) which can successfully start the PWM on pic16 devices whould be useful.

¿Fue útil?

Solución

CCP1 Pin was not being correctly set. 'TRISB2 = 0' should be 'TRISC2 = 0'

// Timer 2 (PWM timebase)
TMR2 = 0;    //Clear timer
TOUTPS0 = 0;
TOUTPS1 = 0;
TOUTPS2 = 0;
TOUTPS3 = 1; //Postscaler -> 8
T2CKPS0 = 0;
T2CKPS1 = 1; //Prescaler -> 16
TMR2IF  = 0;
TMR2IE  = 1; //Interrupt
PR2 = 233;   //~2.5ms

//PWM1 config
CCPR1L = 0xFF;
CCP1X = 1;
CCP1Y = 1; //PWM1 duty cycle 
TRISC2 = 0; //Previously was TRISB2
TMR2ON = 1;
CCP1CON = 0x0c; //CPP1 is a PWM
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