outcompare_squarewave.c - generates a square wave using output compare (PIC24F/H/E families)

Generates a square wave using output compare (OC1). The example uses the Timer2 clock2 and is compatible with the PIC24F/H/E families

 
#include "pic24_all.h"


#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 = usToU16Ticks(SQWAVE_PERIOD/2,getTimerPrescale(T2CONbits)) -1;
  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
  //initialize the compare register to 1/4 the squarewave period
  //assumes TIMER2 initialized before OC1 so PRE bits are set
  OC1R = usToU16Ticks(SQWAVE_PERIOD/4, getTimerPrescale(T2CONbits));
#ifdef OC1CON1
  OC1CON1 = OC_TIMER2_SRC |      //Timer2 source
            OC_TOGGLE_PULSE;     //single compare toggle
  OC1CON2 = OC_SYNCSEL_TIMER2;   //synchronize to timer2
#else
  OC1CON = OC_TIMER2_SRC |      //Timer2 source
           OC_TOGGLE_PULSE;     //single compare toggle
#endif
}

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
}