diff options
Diffstat (limited to 'stmhal/timer.c')
| -rw-r--r-- | stmhal/timer.c | 105 |
1 files changed, 69 insertions, 36 deletions
diff --git a/stmhal/timer.c b/stmhal/timer.c index 93f66c6314..026d11c815 100644 --- a/stmhal/timer.c +++ b/stmhal/timer.c @@ -268,37 +268,84 @@ void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim) { STATIC const mp_obj_type_t pyb_timer_channel_type; +// This is the largest value that we can multiply by 100 and have the result +// fit in a uint32_t. +#define MAX_PERIOD_DIV_100 42949672 + +// Helper function for determining the period used for calculating percent +STATIC uint32_t compute_period(pyb_timer_obj_t *self) { + // In center mode, compare == period corresponds to 100% + // In edge mode, compare == (period + 1) corresponds to 100% + uint32_t period = (__HAL_TIM_GetAutoreload(&self->tim) & TIMER_CNT_MASK(self)); + if (period != 0xffffffff) { + if (self->tim.Init.CounterMode == TIM_COUNTERMODE_UP || + self->tim.Init.CounterMode == TIM_COUNTERMODE_DOWN) { + // Edge mode + period++; + } + } + return period; +} + // Helper function to compute PWM value from timer period and percent value. -// 'val' can be an int or a float between 0 and 100 (out of range values are -// clamped). -STATIC uint32_t compute_pwm_value_from_percent(uint32_t period, mp_obj_t val) { +// 'percent_in' can be an int or a float between 0 and 100 (out of range +// values are clamped). +STATIC uint32_t compute_pwm_value_from_percent(uint32_t period, mp_obj_t percent_in) { uint32_t cmp; if (0) { #if MICROPY_PY_BUILTINS_FLOAT - } else if (MP_OBJ_IS_TYPE(val, &mp_type_float)) { - cmp = mp_obj_get_float(val) / 100.0 * period; + } else if (MP_OBJ_IS_TYPE(percent_in, &mp_type_float)) { + float percent = mp_obj_get_float(percent_in); + if (percent <= 0.0) { + cmp = 0; + } else if (percent >= 100.0) { + cmp = period; + } else { + cmp = percent / 100.0 * ((float)period); + } #endif } else { // For integer arithmetic, if period is large and 100*period will // overflow, then divide period before multiplying by cmp. Otherwise // do it the other way round to retain precision. - // TODO we really need an mp_obj_get_uint_clamped function here so - // that we can get long-int values as large as 0xffffffff. - cmp = mp_obj_get_int(val); - if (period > (1 << 31) / 100) { - cmp = cmp * (period / 100); + mp_int_t percent = mp_obj_get_int(percent_in); + if (percent <= 0) { + cmp = 0; + } else if (percent >= 100) { + cmp = period; + } else if (period > MAX_PERIOD_DIV_100) { + cmp = (uint32_t)percent * (period / 100); } else { - cmp = (cmp * period) / 100; + cmp = ((uint32_t)percent * period) / 100; } } - if (cmp < 0) { - cmp = 0; - } else if (cmp > period) { - cmp = period; - } return cmp; } +// Helper function to compute percentage from timer perion and PWM value. +STATIC mp_obj_t compute_percent_from_pwm_value(uint32_t period, uint32_t cmp) { + #if MICROPY_PY_BUILTINS_FLOAT + float percent; + if (cmp > period) { + percent = 100.0; + } else { + percent = (float)cmp * 100.0 / ((float)period); + } + return mp_obj_new_float(percent); + #else + mp_int_t percent; + if (cmp > period) { + percent = 100; + } else if (period > MAX_PERIOD_DIV_100) { + // We divide the top and bottom by 128, and then do the math. + percent = (cmp / 128) * 100 / (period / 128); + } else { + percent = cmp * 100 / period; + } + return mp_obj_new_int(percent); + #endif +} + STATIC void pyb_timer_print(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t self_in, mp_print_kind_t kind) { pyb_timer_obj_t *self = self_in; @@ -696,13 +743,7 @@ STATIC mp_obj_t pyb_timer_channel(mp_uint_t n_args, const mp_obj_t *args, mp_map oc_config.OCMode = channel_mode_info[chan->mode].oc_mode; if (vals[3].u_obj != mp_const_none) { // pulse width percent given - uint32_t period = (__HAL_TIM_GetAutoreload(&self->tim) & TIMER_CNT_MASK(self)) + 1; - // For 32-bit timer, maximum period + 1 will overflow. In that - // case we set the period back to 0xffffffff which will give very - // close to the correct result for the percentage calculation. - if (period == 0) { - period = 0xffffffff; - } + uint32_t period = compute_period(self); oc_config.Pulse = compute_pwm_value_from_percent(period, vals[3].u_obj); } else { // use absolute pulse width value (defaults to 0 if nothing given) @@ -917,6 +958,9 @@ STATIC void pyb_timer_channel_print(void (*print)(void *env, const char *fmt, .. /// Get or set the pulse width value associated with a channel. /// capture, compare, and pulse_width are all aliases for the same function. /// pulse_width is the logical name to use when the channel is in PWM mode. +/// +/// In edge aligned mode, a pulse_width of `period + 1` corresponds to a duty cycle of 100% +/// In center aligned mode, a pulse width of `period` corresponds to a duty cycle of 100% STATIC mp_obj_t pyb_timer_channel_capture_compare(mp_uint_t n_args, const mp_obj_t *args) { pyb_timer_channel_obj_t *self = args[0]; if (n_args == 1) { @@ -938,22 +982,11 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(pyb_timer_channel_capture_compare_obj /// a duty cycle of 25%. STATIC mp_obj_t pyb_timer_channel_pulse_width_percent(mp_uint_t n_args, const mp_obj_t *args) { pyb_timer_channel_obj_t *self = args[0]; - uint32_t period = (__HAL_TIM_GetAutoreload(&self->timer->tim) & TIMER_CNT_MASK(self->timer)) + 1; - // For 32-bit timer, maximum period + 1 will overflow. In that case we set - // the period back to 0xffffffff which will give very close to the correct - // result for the percentage calculation. - if (period == 0) { - period = 0xffffffff; - } + uint32_t period = compute_period(self->timer); if (n_args == 1) { // get uint32_t cmp = __HAL_TIM_GetCompare(&self->timer->tim, TIMER_CHANNEL(self)) & TIMER_CNT_MASK(self->timer); - #if MICROPY_PY_BUILTINS_FLOAT - return mp_obj_new_float((float)cmp / (float)period * 100.0); - #else - // TODO handle overflow of multiplication for 32-bit timer - return mp_obj_new_int(cmp * 100 / period); - #endif + return compute_percent_from_pwm_value(period, cmp); } else { // set uint32_t cmp = compute_pwm_value_from_percent(period, args[1]); |