Posted on May 07, 2014 at 23:04I am trying to build a scheduler on top of a 1MHz tim5 32 bit timer operating in one pulse mode:
void initMicrosecondTimer(void) {
RCC ->APB1ENR |= RCC_APB1ENR_TIM5EN; // Enable TIM5 clock
nvicEnableVector(HW_TIMER_IRQ, CORTEX_PRIORITY_MASK(HW_TIMER_PRIORITY));
TIM->DIER |= TIM_DIER_UIE; // Enable interrupt on update event
TIM->CR1 |= TIM_CR1_OPM; // one pulse mode: count down ARR and stop
TIM->CR1 &= ~TIM_CR1_ARPE; /* ARR register is NOT buffered, allows to update timer's period on-fly. */
TIM->PSC = 84 - 1; // 168MHz / 2 / 84 = 1MHz, each tick is a microsecond
}
/**
* sets the alarm to the specified number of microseconds from now.
* This function should be invoked under kernel lock which would disable interrupts.
*/
void setHardwareUsTimer(int timeUs) {
TIM->ARR = timeUs - 1;
TIM->EGR |= TIM_EGR_UG; // generate an update event to reload timer's counter value
TIM->CR1 |= TIM_CR1_CEN; // restart timer
lastSetTimerTime = getTimeNowUs();
isTimerPending = TRUE;
timerRestartCounter++;
}
Full file:
https://sourceforge.net/p/rusefi/code/HEAD/tree/trunk/firmware/hw_layer/microsecond_timer.c Problem: while everything works as expected in case of timeUs parameter above 300, I am not getting the expected callback for smaller timeUs parameter values like 5 or 11. Just for clarity: I am not even trying to constantly invoke 5us, 5us, 5us, 5us - even a single 5us between 300us invocations fails.
Currently I am trying relatively low #define HW_TIMER_PRIORITY 12 but I was still expecting the callback to happen eventually?
Please advice how can I get the callback to happen, even if it would be a bit late.
