ledflash_timer.c - uses a periodic timer interrupt to flash an LED.ΒΆ

Demonstrates use of a periodic interrupt to flash an LED. Timer3 is configured for a 150 ms interrupt to flash an LED on RB14.

 
#include "pic24_all.h"

LED1

#define CONFIG_LED1() CONFIG_RB14_AS_DIG_OUTPUT()
#define LED1  (_LATB14)     //led1 state

Interrupt Service Routine for Timer3

void _ISR _T3Interrupt(void) {
  LED1 = !LED1; //toggle the LED
  _T3IF = 0;    //clear the timer interrupt bit
}

in ms

#define ISR_PERIOD (150)

void  configTimer3(void) {

Ensure that Timer2,3 configured as separate timers.

  T2CONbits.T32 = 0;     // 32-bit mode off

T3CON set like this for documentation purposes. Could be replaced by T3CON = 0x0030

  T3CON = T3_OFF | T3_IDLE_CON | T3_GATE_OFF
          | T3_SOURCE_INT
          | T3_PS_1_256 ;  //results in T3CON= 0x0030
  PR3 = msToU16Ticks (ISR_PERIOD, getTimerPrescale(T3CONbits)) - 1;
  TMR3  = 0;                       //clear timer3 value
  _T3IF = 0;                       //clear interrupt flag
  _T3IP = 1;                       //choose a priority
  _T3IE = 1;                       //enable the interrupt
  T3CONbits.TON = 1;               //turn on the timer
}

int main(void) {
  configBasic(HELLO_MSG);
  /** GPIO config ***************************/
  CONFIG_LED1();       //config the LED
  LED1 = 1;
  /** Config the Timer, use Timer3***********/
  configTimer3();
  while (1) {

Enter idle mode while waiting for timer to go off Timer interrupt will wake us from idle mode

    IDLE();  //macro for  __asm__ volatile ("pwrsav #1")
  }

End program

  return 0;
}