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[stm32f0xx] Fix prescaler value.

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As specified in ST reference manual RM0091, the prescaling factor
applied by timers is 1 plus the value in the corresponding prescaler
register. (See section 17.4.11 for TIM1, and analogous sections for
other timers.)

This change causes stm32_timer_capture_setup to take the prescaling
factor as input rather than the register value.
This commit is contained in:
Onath Claridge
2020-07-17 16:02:32 -07:00
committed by Travis Geiselbrecht
parent 9d07949891
commit c629d762a3
2 changed files with 8 additions and 1 deletions
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3
platform/stm32f0xx/include/platform/timer_capture.h
View File

@@ -33,6 +33,9 @@ typedef struct {
} stm32_timer_capture_t;
// Set tc->chan[] cb and flags before calling.
//
// `prescaler` is the desired prescaling factor and must be positive. The value stored in the
// prescaler register will be `prescaler - 1` (see ST reference manual RM0091, section 18.4.11).
status_t stm32_timer_capture_setup(stm32_timer_capture_t *tc, int timer, uint16_t prescaler);
uint64_t stm32_timer_capture_get_counter(stm32_timer_capture_t *tc);

6
platform/stm32f0xx/timer_capture.c
View File

@@ -316,6 +316,8 @@ void stm32_TIM17_IRQ(void) {
}
status_t stm32_timer_capture_setup(stm32_timer_capture_t *tc, int timer, uint16_t prescaler) {
assert(prescaler > 0);
tc->config = stm32_timer_get_config(timer);
if (tc->config == NULL) {
return ERR_NOT_FOUND;
@@ -329,7 +331,9 @@ status_t stm32_timer_capture_setup(stm32_timer_capture_t *tc, int timer, uint16_
spin_lock_init(&tc->overflow_lock);
tc->config->regs->CR1 = 0;
tc->config->regs->PSC = prescaler;
// The prescaler value applied by hardware is PSC + 1.
tc->config->regs->PSC = prescaler > 0 ? prescaler - 1 : 0;
uint32_t dier = TIM_DIER_UIE;