PWM output problem

[pool2883]

Hallo,

Habe ursprünglich die frage auf englisch verfasst, auf Deutsch zu anzworten ist kein Problem. Benütze den C18 compiler von Microchip.

I have a problem generating consistent PWM outputs.
Specifically, the output duty cycle varies every time I call the SetDCPWM1() function in my code below. Upon checking the RC2/CCP1 pin with the Oscilloscope, the PWM period stays constant, but the duty cycle is different in the while()-loop every time called, although the argument is the same

More strangely, my RB4 output pin (which I use to Enable a H-Bridge Driver) after some seconds drops low - although its state shouldnt change in the while loop.

Anyone have any idea? I´m using an external 6MHz Quarz, each pin connected also in parallell with two 27pF connected to GND. The PIC is a PIC18F248.


#include <p18f248.h>
#include <stdlib.h>
#include <string.h>
#include <pwm.h>
#include <timers.h>
#include <delays.h>

#pragma config OSC = HS
#pragma config PWRT = ON
#pragma config BOR = OFF
#pragma config WDT = OFF
#pragma config LVP = OFF

#pragma code

void main(void)
{
OpenPWM1(0xf0);
OpenTimer2(T2_PS_1_1 & T2_POST_1_10 & TIMER_INT_OFF);

PORTC = 0; // Clear PORTC
TRISC = 0xdb; // Make RC2/CCP1 and RC5(remove later) outputs

LATB = 0x10; //0x10 = 00010000b = bit4 (RB4) of PORTB Register ON
TRISB = 0xef; //0xEF = 11101111h = bit4 (RB4) of TRISB sets Output

while (1)
{
Delay10KTCYx(255);
SetDCPWM1(600);
}
}

//END OF PROGRAM

[Jaipur]

More strangely, my RB4 output pin (which I use to Enable a H-Bridge Driver) after some seconds drops low - although its state shouldnt change in the while loop.

ich habe gerade im datenblatt vom PIC18F248 gelesen das der RA4 ein open-drain IO ist, wurde in der hardwareschaltung daran gedacht einen pull-up an den RA4 zu legen?