/** Initialize the high frequency ticker
*
*/
void us_ticker_init(void)
{
/* Common for ticker/timer. */
uint32_t busClock;
/* Structure to initialize PIT. */
pit_config_t pitConfig;
PIT_GetDefaultConfig(&pitConfig);
PIT_Init(PIT, &pitConfig);
busClock = CLOCK_GetFreq(kCLOCK_BusClk);
/* Let the timer to count if re-init. */
if (!us_ticker_inited) {
PIT_SetTimerPeriod(PIT, kPIT_Chnl_0, busClock / 1000000 - 1);
PIT_SetTimerPeriod(PIT, kPIT_Chnl_1, 0xFFFFFFFF);
PIT_SetTimerChainMode(PIT, kPIT_Chnl_1, true);
PIT_StartTimer(PIT, kPIT_Chnl_0);
PIT_StartTimer(PIT, kPIT_Chnl_1);
}
/* Configure interrupt generation counters and disable ticker interrupts. */
PIT_StopTimer(PIT, kPIT_Chnl_3);
PIT_StopTimer(PIT, kPIT_Chnl_2);
PIT_SetTimerPeriod(PIT, kPIT_Chnl_2, busClock / 1000000 - 1);
PIT_SetTimerChainMode(PIT, kPIT_Chnl_3, true);
NVIC_SetVector(PIT3_IRQn, (uint32_t) pit_isr);
NVIC_EnableIRQ(PIT3_IRQn);
PIT_DisableInterrupts(PIT, kPIT_Chnl_3, kPIT_TimerInterruptEnable);
us_ticker_inited = true;
}
static void pit_isr(void)
{
PIT_ClearStatusFlags(PIT, kPIT_Chnl_3, PIT_TFLG_TIF_MASK);
PIT_ClearStatusFlags(PIT, kPIT_Chnl_2, PIT_TFLG_TIF_MASK);
PIT_StopTimer(PIT, kPIT_Chnl_2);
PIT_StopTimer(PIT, kPIT_Chnl_3);
us_ticker_irq_handler();
}
void us_ticker_free(void)
{
PIT_StopTimer(PIT, kPIT_Chnl_1);
PIT_StopTimer(PIT, kPIT_Chnl_0);
TPM_DisableInterrupts(TPM2, kTPM_TimeOverflowInterruptEnable);
NVIC_DisableIRQ(TPM2_IRQn);
us_ticker_inited = false;
}
void us_ticker_set_interrupt(timestamp_t timestamp)
{
uint32_t now_us, delta_us;
now_us = us_ticker_read();
delta_us = timestamp >= now_us ? timestamp - now_us : (uint32_t)((uint64_t)timestamp + 0xFFFFFFFF - now_us);
PIT_StopTimer(PIT, kPIT_Chnl_3);
PIT_StopTimer(PIT, kPIT_Chnl_2);
PIT_SetTimerPeriod(PIT, kPIT_Chnl_3, (uint32_t)delta_us);
PIT_EnableInterrupts(PIT, kPIT_Chnl_3, kPIT_TimerInterruptEnable);
PIT_StartTimer(PIT, kPIT_Chnl_3);
PIT_StartTimer(PIT, kPIT_Chnl_2);
}
/** Set interrupt for specified timestamp
*
* @param timestamp The time in ticks when interrupt should be generated
*/
void us_ticker_set_interrupt(timestamp_t timestamp)
{
/* We get here absolute interrupt time which takes into account counter overflow.
* Since we use additional count-down timer to generate interrupt we need to calculate
* load value based on time-stamp.
*/
const uint32_t now_ticks = us_ticker_read();
uint32_t delta_ticks =
timestamp >= now_ticks ? timestamp - now_ticks : (uint32_t)((uint64_t) timestamp + 0xFFFFFFFF - now_ticks);
if (delta_ticks == 0) {
/* The requested delay is less than the minimum resolution of this counter. */
delta_ticks = 1;
}
PIT_StopTimer(PIT, kPIT_Chnl_3);
PIT_StopTimer(PIT, kPIT_Chnl_2);
PIT_SetTimerPeriod(PIT, kPIT_Chnl_3, delta_ticks);
PIT_EnableInterrupts(PIT, kPIT_Chnl_3, kPIT_TimerInterruptEnable);
PIT_StartTimer(PIT, kPIT_Chnl_3);
PIT_StartTimer(PIT, kPIT_Chnl_2);
}
