main.cpp

00001 #include "mbed.h"
00002 
00003 volatile unsigned int ticks = 0;
00004 
00005 DigitalOut led(LED_BLUE);
00006 
00007 extern "C" void lptmr_isr(void) {
00008     // write 1 to TCF to clear the LPT timer compare flag
00009     LPTMR0->CSR |= LPTMR_CSR_TCF_MASK;
00010 
00011     ticks++;
00012 }
00013 
00014 int main() {
00015     /* Clock the timer */
00016     SIM->SCGC5 |= SIM_SCGC5_LPTMR_MASK;
00017 
00018     /* Reset */
00019     LPTMR0->CSR = 0;
00020 
00021     /* Compare value */
00022     LPTMR0->CMR = 1000;
00023 
00024     /* Enable interrupt */
00025     LPTMR0->CSR |= LPTMR_CSR_TIE_MASK;
00026 
00027     /* Set interrupt handler */
00028     NVIC_SetVector(LPTimer_IRQn, (uint32_t)lptmr_isr);
00029     NVIC_EnableIRQ(LPTimer_IRQn);
00030 
00031     /* select LPO for RTC and LPTMR */
00032     LPTMR0->PSR = LPTMR_PSR_PCS(3);       // ERCLK32K -> 8MHz
00033     LPTMR0->PSR |= LPTMR_PSR_PRESCALE(2); // divide by 8
00034 
00035     /* Start the timer */
00036     LPTMR0->CSR |= LPTMR_CSR_TEN_MASK;
00037 
00038     led = 0;
00039     while (true) {
00040         wait(1);
00041         led = 1;
00042         printf("%d\n", ticks);
00043 
00044         wait(1);
00045         led = 0;
00046         printf("%d\n", ticks);
00047     }
00048 }