diff options
| -rw-r--r-- | stmhal/timer.c | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/stmhal/timer.c b/stmhal/timer.c index 30bcf2c079..b0b35740f5 100644 --- a/stmhal/timer.c +++ b/stmhal/timer.c @@ -274,8 +274,11 @@ STATIC mp_obj_t pyb_timer_init_helper(pyb_timer_obj_t *self, uint n_args, const tim_clock = HAL_RCC_GetPCLK1Freq(); } - // compute the prescaler value so TIM triggers at freq-Hz - // dpgeorge: I don't understand why we need to multiply tim_clock by 2 + // Compute the prescaler value so TIM triggers at freq-Hz + // On STM32F405/407/415/417 there are 2 cases for how the clock freq is set. + // If the APB prescaler is 1, then the timer clock is equal to its respective + // APB clock. Otherwise (APB prescaler > 1) the timer clock is twice its + // respective APB clock. See DM00031020 Rev 4, page 115. uint32_t period = MAX(1, 2 * tim_clock / vals[0].u_int); uint32_t prescaler = 1; while (period > 0xffff) { |