main.cpp

00001 #include "mbed.h"
00002 
00003 extern "C" {
00004 volatile uint32_t msTicks;
00005 
00006 void SysTick_Handler(void) {
00007     msTicks++;
00008 }
00009 
00010 void Delay(uint32_t dlyTicks) {
00011     uint32_t curTicks;
00012 
00013     curTicks = msTicks;
00014     while ((msTicks - curTicks) < dlyTicks);
00015 }
00016 }
00017 
00018 int main() {
00019     SysTick_Config(SystemCoreClock / 1000);
00020 
00021     SIM->SCGC6 |= SIM_SCGC6_PIT_MASK;   // Clock PIT
00022     PIT->MCR = 0;                       // Enable PIT
00023 
00024     // Timer 1
00025     PIT->CHANNEL[1].LDVAL = 0xFFFFFFFF;
00026     PIT->CHANNEL[1].TCTRL = 0x0;                 // Disable Interrupts
00027     PIT->CHANNEL[1].TCTRL |= PIT_TCTRL_CHN_MASK; // Chain to timer 0
00028     PIT->CHANNEL[1].TCTRL |= PIT_TCTRL_TEN_MASK; // Start timer 1
00029 
00030     // Timer 2
00031     PIT->CHANNEL[0].LDVAL = 0xFFFFFFFF;
00032     PIT->CHANNEL[0].TCTRL = PIT_TCTRL_TEN_MASK;  // Start timer 0, disable interrupts
00033 
00034     DigitalOut led(LED_BLUE);
00035     while (true) {
00036         Delay(1000);
00037         led = !led;
00038 
00039         uint64_t ticks = (uint64_t)PIT->LTMR64H << 32;
00040         ticks         |= (uint64_t)PIT->LTMR64L;
00041         printf("ticks: 0x%x%x\n", (uint32_t)(ticks>>32), (uint32_t)(ticks & 0xFFFFFFFF));
00042 
00043         ticks = (~ticks) / 24;
00044         uint32_t us = (uint32_t)(0xFFFFFFFF & ticks);
00045 
00046         printf("us   : 0x%x\n", us);
00047     }
00048 }