輸出頻率和分辨率要符合一定的規則:一定要注意!
舊算法:
esp_err_t ledc_set_freq(ledc_mode_t speed_mode, ledc_timer_t timer_num, uint32_t freq_hz)
{
LEDC_ARG_CHECK(speed_mode < LEDC_SPEED_MODE_MAX, "speed_mode");
portENTER_CRITICAL(&ledc_spinlock);
esp_err_t ret = ESP_OK;
uint32_t clock_divider = 0;
uint32_t duty_resolution = LEDC.timer_group[speed_mode].timer[timer_num].conf.duty_resolution;
uint32_t timer_source_clk = LEDC.timer_group[speed_mode].timer[timer_num].conf.tick_sel;
uint32_t precision = (0x1 << duty_resolution);
if (timer_source_clk == LEDC_APB_CLK) {
clock_divider = ((uint64_t) LEDC_APB_CLK_HZ << 8) / freq_hz / precision;
} else {
clock_divider = ((uint64_t) LEDC_REF_CLK_HZ << 8) / freq_hz / precision;
}
if (clock_divider <= 256 || clock_divider > LEDC_DIV_NUM_HSTIMER0) {
ESP_LOGE(LEDC_TAG, "div param err,div_param=%u", clock_divider);
ret = ESP_FAIL;
}
LEDC.timer_group[speed_mode].timer[timer_num].conf.clock_divider = clock_divider;
ledc_ls_timer_update(speed_mode, timer_num);
portEXIT_CRITICAL(&ledc_spinlock);
return ret;
}
新算法:
static esp_err_t ledc_set_timer_div(ledc_mode_t speed_mode, ledc_timer_t timer_num, ledc_clk_cfg_t clk_cfg, int freq_hz, int duty_resolution)
{
uint32_t div_param = 0;
uint32_t precision = ( 0x1 << duty_resolution );
ledc_clk_src_t timer_clk_src = LEDC_APB_CLK;
// Calculate the divisor
// User specified source clock(RTC8M_CLK) for low speed channel
if ((speed_mode == LEDC_LOW_SPEED_MODE) && (clk_cfg == LEDC_USE_RTC8M_CLK)) {
if(s_ledc_slow_clk_8M == 0) {
if (ledc_slow_clk_calibrate() == false) {
goto error;
}
}
div_param = ( (uint64_t) s_ledc_slow_clk_8M << 8 ) / freq_hz / precision;
} else {
// Automatically select APB or REF_TICK as the source clock.
if (clk_cfg == LEDC_AUTO_CLK) {
// Try calculating divisor based on LEDC_APB_CLK
div_param = ( (uint64_t) LEDC_APB_CLK_HZ << 8 ) / freq_hz / precision;
if (div_param > LEDC_DIV_NUM_HSTIMER0_V) {
// APB_CLK results in divisor which too high. Try using REF_TICK as clock source.
timer_clk_src = LEDC_REF_TICK;
div_param = ((uint64_t) LEDC_REF_CLK_HZ << 8) / freq_hz / precision;
} else if (div_param < 256) {
// divisor is too low
goto error;
}
// User specified source clock(LEDC_APB_CLK_HZ or LEDC_REF_TICK)
} else {
timer_clk_src = (clk_cfg == LEDC_USE_APB_CLK) ? LEDC_APB_CLK : LEDC_REF_TICK;
uint32_t sclk_freq = (clk_cfg == LEDC_USE_APB_CLK) ? LEDC_APB_CLK_HZ : LEDC_REF_CLK_HZ;
div_param = ( (uint64_t) sclk_freq << 8 ) / freq_hz / precision;
}
}
if (div_param < 256 || div_param > LEDC_DIV_NUM_LSTIMER0_V) {
goto error;
}
// For low speed channels, if RTC_8MCLK is used as the source clock, the `slow_clk_sel` register should be cleared, otherwise it should be set.
if (speed_mode == LEDC_LOW_SPEED_MODE) {
LEDC.conf.slow_clk_sel = (clk_cfg == LEDC_USE_RTC8M_CLK) ? 0 : 1;
}
//Set the divisor
ledc_timer_set(speed_mode, timer_num, div_param, duty_resolution, timer_clk_src);
// reset the timer
ledc_timer_rst(speed_mode, timer_num);
return ESP_OK;
error:
ESP_LOGE(LEDC_TAG, "requested frequency and duty resolution can not be achieved, try reducing freq_hz or duty_resolution. div_param=%d",
(uint32_t ) div_param);
return ESP_FAIL;
}
esp_err_t ledc_timer_config(const ledc_timer_config_t* timer_conf)
{
LEDC_ARG_CHECK(timer_conf != NULL, "timer_conf");
uint32_t freq_hz = timer_conf->freq_hz;
uint32_t duty_resolution = timer_conf->duty_resolution;
uint32_t timer_num = timer_conf->timer_num;
uint32_t speed_mode = timer_conf->speed_mode;
LEDC_ARG_CHECK(speed_mode < LEDC_SPEED_MODE_MAX, "speed_mode");
LEDC_ARG_CHECK(!((timer_conf->clk_cfg == LEDC_USE_RTC8M_CLK) && (speed_mode != LEDC_LOW_SPEED_MODE)), "Only low speed channel support RTC8M_CLK");
periph_module_enable(PERIPH_LEDC_MODULE);
if (freq_hz == 0 || duty_resolution == 0 || duty_resolution >= LEDC_TIMER_BIT_MAX) {
ESP_LOGE(LEDC_TAG, "freq_hz=%u duty_resolution=%u", freq_hz, duty_resolution);
return ESP_ERR_INVALID_ARG;
}
if (timer_num > LEDC_TIMER_3) {
ESP_LOGE(LEDC_TAG, "invalid timer #%u", timer_num);
return ESP_ERR_INVALID_ARG;
}
return ledc_set_timer_div(speed_mode, timer_num, timer_conf->clk_cfg, freq_hz, duty_resolution);
}
注意:LEDC_LOW_SPEED_MODE模式只支持8M時鐘。