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stm32/timer: Enable ARPE so that timer freq can be changed smoothly.

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The timer prescaler is buffered by default, and this patch enables ARPE
which buffers the auto-reload register.  With both of these registers
buffered it's now possible to smoothly change the timer's frequency and
have a smoothly varying PWM output.
This commit is contained in:
Damien George 2017-09-25 15:25:08 +10:00
parent 4a314a6f63
commit d29b709642
1 changed files with 6 additions and 8 deletions
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14
ports/stm32/timer.c
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@ -620,6 +620,12 @@ STATIC mp_obj_t pyb_timer_init_helper(pyb_timer_obj_t *self, size_t n_args, cons
#endif
config_deadtime(self, args[6].u_int);
}
// Enable ARPE so that the auto-reload register is buffered.
// This allows to smoothly change the frequency of the timer.
self->tim.Instance->CR1 |= TIM_CR1_ARPE;
// Start the timer running
if (args[5].u_obj == mp_const_none) {
HAL_TIM_Base_Start(&self->tim);
} else {
@ -1121,10 +1127,6 @@ STATIC mp_obj_t pyb_timer_freq(size_t n_args, const mp_obj_t *args) {
uint32_t prescaler = compute_prescaler_period_from_freq(self, args[1], &period);
self->tim.Instance->PSC = prescaler;
__HAL_TIM_SetAutoreload(&self->tim, period);
// Reset the counter to zero. Otherwise, if counter >= period it will
// continue counting until it wraps (at either 16 or 32 bits depending
// on the timer).
__HAL_TIM_SetCounter(&self->tim, 0);
return mp_const_none;
}
}
@ -1155,10 +1157,6 @@ STATIC mp_obj_t pyb_timer_period(size_t n_args, const mp_obj_t *args) {
} else {
// set
__HAL_TIM_SetAutoreload(&self->tim, mp_obj_get_int(args[1]) & TIMER_CNT_MASK(self));
// Reset the counter to zero. Otherwise, if counter >= period it will
// continue counting until it wraps (at either 16 or 32 bits depending
// on the timer).
__HAL_TIM_SetCounter(&self->tim, 0);
return mp_const_none;
}
}