outcompare_contpulse.c - Generate an asymmetric square wave using output compare (OC1), continuous pulse mode

Generate an asymmetric square wave using output compare (OC1), continuous pulse mode. If you wish greater accuracy, then use a clock choice with an external crystal, such as: CLOCK_CONFIG=PRIPLL_8MHzCrystal_40MHzFCY Remove this macro if you wish to use the internal oscillator.

 
#include "pic24_all.h"

#ifndef SQWAVE_PWHIGH
#define SQWAVE_PWHIGH 2000   // desired PW High, in us
#endif
#ifndef SQWAVE_PERIOD
#define SQWAVE_PERIOD 20000  // desired period, in us
#endif


void  configTimer2(void) {
  T2CON = T2_OFF | T2_IDLE_CON | T2_GATE_OFF
          | T2_32BIT_MODE_OFF
          | T2_SOURCE_INT
          | T2_PS_1_64 ;  //1 tick = 1.6 us at FCY=40 MHz
  PR2 = usToU16Ticks(SQWAVE_PERIOD, getTimerPrescale(T2CONbits));
  TMR2  = 0;       //clear timer2 value
}

void configOutputCompare1(void) {
  T2CONbits.TON = 0;       //disable Timer when configuring Output compare
  CONFIG_RB8_AS_DIG_OUTPUT();
#if (defined(__dsPIC33E__) || defined(__PIC24E__))
  CONFIG_OC1_TO_RP(40);        //map OC1 to RB8/RP40
#else
  CONFIG_OC1_TO_RP(8);        //map OC1 to RB8/RP13
#endif
//initialized the primary,secondary compare registers
//assumes TIMER2 initialized before OC1 so PRE bits are set
  OC1R = 0;   //go high when Timer2 == 0
  OC1RS = usToU16Ticks(SQWAVE_PWHIGH, getTimerPrescale(T2CONbits)); //go low when Timer2 == u16_sqwavePWHighTicks
//turn on the compare toggle mode using Timer2
#if (defined(__dsPIC33E__) || defined(__PIC24E__))
  OC1CON1 = OC_TIMER2_SRC |     //Timer2 source
            OC_CONTINUE_PULSE;  //Continuous pulse mode
  OC1CON2 = 0x000C;           //sync source is Timer2.
#else
  OC1CON = OC_TIMER2_SRC |     //Timer2 source
           OC_CONTINUE_PULSE;  //Continuous pulse mode
#endif
  _OC1IF = 0;
}

int main (void) {
  configBasic(HELLO_MSG);
  configTimer2();
  configOutputCompare1();
  T2CONbits.TON = 1;       //turn on Timer2 to start sqwave
  while (1) doHeartbeat(); //nothing to do, squarewave generated in hardware
}