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HardwareTimer: Fix ARR and CCRx computation #902

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merged 1 commit into from
Jan 30, 2020
+26 −10
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HardwareTimer: Fix ARR and CCRx computation #902

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36 changes: 26 additions & 10 deletions cores/arduino/HardwareTimer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -87,7 +87,7 @@ HardwareTimer::HardwareTimer(TIM_TypeDef *instance)

/* Configure timer with some default values */
_timerObj.handle.Init.Prescaler = 0;
_timerObj.handle.Init.Period = 0xFFFF; // 16bit max value
_timerObj.handle.Init.Period = MAX_RELOAD;
_timerObj.handle.Init.CounterMode = TIM_COUNTERMODE_UP;
_timerObj.handle.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
#if defined(TIM_RCR_REP)
Expand Down Expand Up @@ -452,6 +452,7 @@ uint32_t HardwareTimer::getOverflow(TimerFormat_t format)
void HardwareTimer::setOverflow(uint32_t overflow, TimerFormat_t format)
{
uint32_t ARR_RegisterValue;
uint32_t PeriodTicks;
uint32_t Prescalerfactor;
uint32_t period_cyc;
// Remark: Hardware register correspond to period count-1. Example ARR register value 9 means period of 10 timer cycle
Expand All @@ -460,20 +461,27 @@ void HardwareTimer::setOverflow(uint32_t overflow, TimerFormat_t format)
period_cyc = overflow * (getTimerClkFreq() / 1000000);
Prescalerfactor = (period_cyc / 0x10000) + 1;
LL_TIM_SetPrescaler(_timerObj.handle.Instance, Prescalerfactor - 1);
ARR_RegisterValue = (period_cyc / Prescalerfactor) - 1;
PeriodTicks = period_cyc / Prescalerfactor;
break;
case HERTZ_FORMAT:
period_cyc = getTimerClkFreq() / overflow;
Prescalerfactor = (period_cyc / 0x10000) + 1;
LL_TIM_SetPrescaler(_timerObj.handle.Instance, Prescalerfactor - 1);
ARR_RegisterValue = (period_cyc / Prescalerfactor) - 1;
PeriodTicks = period_cyc / Prescalerfactor;
break;
case TICK_FORMAT:
default :
ARR_RegisterValue = overflow - 1;
PeriodTicks = overflow;
break;
}

if (PeriodTicks > 0) {
// The register specifies the maximum value, so the period is really one tick longer
ARR_RegisterValue = PeriodTicks - 1;
} else {
// But do not underflow in case a zero period was given somehow.
ARR_RegisterValue = 0;
}
__HAL_TIM_SET_AUTORELOAD(&_timerObj.handle, ARR_RegisterValue);
}

Expand Down Expand Up @@ -520,14 +528,14 @@ void HardwareTimer::setCount(uint32_t counter, TimerFormat_t format)
uint32_t Prescalerfactor = LL_TIM_GetPrescaler(_timerObj.handle.Instance) + 1;
switch (format) {
case MICROSEC_FORMAT:
CNT_RegisterValue = ((counter * (getTimerClkFreq() / 1000000)) / Prescalerfactor) - 1 ;
CNT_RegisterValue = ((counter * (getTimerClkFreq() / 1000000)) / Prescalerfactor);
break;
case HERTZ_FORMAT:
CNT_RegisterValue = (uint32_t)((getTimerClkFreq() / (counter * Prescalerfactor)) - 1);
CNT_RegisterValue = (uint32_t)(getTimerClkFreq() / (counter * Prescalerfactor));
break;
case TICK_FORMAT:
default :
CNT_RegisterValue = counter - 1;
CNT_RegisterValue = counter;
break;
}
__HAL_TIM_SET_COUNTER(&(_timerObj.handle), CNT_RegisterValue);
Expand Down Expand Up @@ -699,11 +707,12 @@ void HardwareTimer::setCaptureCompare(uint32_t channel, uint32_t compare, TimerC

switch (format) {
case MICROSEC_COMPARE_FORMAT:
CCR_RegisterValue = ((compare * (getTimerClkFreq() / 1000000)) / Prescalerfactor) - 1 ;
CCR_RegisterValue = ((compare * (getTimerClkFreq() / 1000000)) / Prescalerfactor);
break;
case HERTZ_COMPARE_FORMAT:
CCR_RegisterValue = (getTimerClkFreq() / (compare * Prescalerfactor)) - 1;
CCR_RegisterValue = getTimerClkFreq() / (compare * Prescalerfactor);
break;
// As per Reference Manual PWM reach 100% with CCRx value strictly greater than ARR (So ARR+1 in our case)
case PERCENT_COMPARE_FORMAT:
CCR_RegisterValue = ((__HAL_TIM_GET_AUTORELOAD(&(_timerObj.handle)) + 1) * compare) / 100;
break;
Expand All @@ -727,10 +736,17 @@ void HardwareTimer::setCaptureCompare(uint32_t channel, uint32_t compare, TimerC
break;
case TICK_COMPARE_FORMAT:
default :
CCR_RegisterValue = compare - 1;
CCR_RegisterValue = compare;
break;
}

// Special case when ARR is set to the max value, it is not possible to set CCRx to ARR+1 to reach 100%
// Then set CCRx to max value. PWM is then 1/0xFFFF = 99.998..%
if ((__HAL_TIM_GET_AUTORELOAD(&(_timerObj.handle)) == MAX_RELOAD)
&& (CCR_RegisterValue == MAX_RELOAD + 1)) {
CCR_RegisterValue = MAX_RELOAD;
}

__HAL_TIM_SET_COMPARE(&(_timerObj.handle), timChannel, CCR_RegisterValue);
}

Expand Down