main.cpp

00001 // k64f rtcisr
00002 // seconds interrupt from RTC compare micros() to check RTC frequency
00003 #include "mbed.h"
00004 
00005 #define micros tmr.read_us
00006 
00007 DigitalOut led(LED_RED);
00008 Timer tmr;
00009 
00010 volatile static unsigned long ticks,us;
00011 static unsigned long us0=0;
00012 
00013 extern "C" void RTC_Seconds_IRQHandler() {
00014     if (us0 == 0) us0 = micros();
00015       else {
00016         ticks++;
00017         us = micros() - us0;
00018     }
00019     led = !led; // toggle led
00020 }
00021 
00022 int main(){
00023     int ppm, tprev=0;
00024 
00025     tmr.start();   // for micros
00026     time(NULL);  // start RTC
00027     RTC_IER = 0x10 ;    //TSIE enable seconds interrupt
00028     NVIC_EnableIRQ(RTC_Seconds_IRQn);
00029     while (true) {
00030         ppm = 1000000*ticks - us;
00031         ppm = 1.e6 * ppm/ (float)us;
00032         printf("%d %d %f %d\n",ticks,ticks-tprev,us*1.e-6,ppm);
00033         wait(2.0);
00034     }
00035 }