outcompare_squarewave_24e.c - generates a square wave using output compare (dsPIC33E/PIC24E only)

Generates a square wave using output compare (OC1). The internal timer uses the Timer2 clock2 and is synchrononized to the OCxRS match event, which means that the internal timer resets to zero on OCxRS match. This example only works on the PIC24E/dsPIC33E

 
#include "pic24_all.h"
#if (! (defined(__dsPIC33E__) || defined(__PIC24E__)))
int main(void) {
  return 0;
}
#else

#define SQWAVE_PERIOD 5000   // desired period, in us
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 = 0xFFFF;    //maximum period
  TMR2  = 0;       //clear timer2 value
}


void configOutputCompare1(void) {
  T2CONbits.TON = 0;       //disable Timer when configuring Output compare
  CONFIG_OC1_TO_RP(RB5_RP);     //map OC1 to RB5
//use OC1R to set pulse high, OC1RS to set pulse low, timer reset on OC1RS match.
//assumes TIMER2 initialized before OC1 so PRE bits are set
  OC1RS = usToU16Ticks(SQWAVE_PERIOD/2, getTimerPrescale(T2CONbits));   //used to reset timer
  OC1R = OC1RS/2;    //1/4 period
  OC1CON1 = OC_TIMER2_SRC |         //Timer2 source
            OC_TOGGLE_PULSE;        //single compare toggle
  OC1CON2 = OC_SYNCSEL_OCxRS;       //reset internal timer when OCxRS match occurs
}

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
}
#endif