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| author | Damien George <damien.p.george@gmail.com> | 2014-08-14 00:30:14 +0100 |
|---|---|---|
| committer | Damien George <damien.p.george@gmail.com> | 2014-08-14 00:30:14 +0100 |
| commit | bf133f7737c99d5359a52abd49e465af863fa734 (patch) | |
| tree | db0e5a2d2856c4b2b5c9287755d8aa4321282560 | |
| parent | 2c781eabbd42b65e6453bad7dcf07344a285f99f (diff) | |
| download | micropython-bf133f7737c99d5359a52abd49e465af863fa734.tar.gz micropython-bf133f7737c99d5359a52abd49e465af863fa734.zip | |
stmhal: Resolve question in comment about timer clock.
| -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) { |