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YanKE01YanKE01
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Merge pull request #25 from YanKE01/feat/add_clac_pwm_freq_duty
feat: add mcpwm capture pwm info example
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‎examples/peripherals/pwm/pwm_info_clac/CMakeLists.txt‎

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# The following five lines of boilerplate have to be in your project's
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# CMakeLists in this exact order for cmake to work correctly
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cmake_minimum_required(VERSION 3.16)
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include($ENV{IDF_PATH}/tools/cmake/project.cmake)
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project(pwm_info_clac)

‎examples/peripherals/pwm/pwm_info_clac/README.md‎

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‎examples/peripherals/pwm/pwm_info_clac/main/CMakeLists.txt‎

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idf_component_register(SRCS "pwm_info_clac.c"
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INCLUDE_DIRS ".")

‎examples/peripherals/pwm/pwm_info_clac/main/Kconfig.projbuild‎

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menu "Example Configuration"
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config PWM_CAPTURE_IO
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int "Pwm Capture Io"
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default 2
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help
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Example used gpio for capture pwm.
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endmenu

‎examples/peripherals/pwm/pwm_info_clac/main/pwm_info_clac.c‎

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/*
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* SPDX-FileCopyrightText: 2021-2022 Espressif Systems (Shanghai) CO LTD
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*
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* SPDX-License-Identifier: Unlicense OR CC0-1.0
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*/
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#include "freertos/FreeRTOS.h"
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#include "freertos/task.h"
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#include "esp_log.h"
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#include "esp_private/esp_clk.h"
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#include "driver/mcpwm_cap.h"
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#include "driver/gpio.h"
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const static char *TAG = "pwm_measure";
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// PWM measurement data structure - only raw tick values in ISR
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typedef struct {
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uint32_t period_ticks;
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uint32_t high_time_ticks;
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} pwm_raw_data_t;
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static bool pwm_measure_callback(mcpwm_cap_channel_handle_t cap_chan, const mcpwm_capture_event_data_t *edata, void *user_data)
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{
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static uint32_t last_pos_edge = 0;
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static uint32_t last_neg_edge = 0;
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static uint32_t period_start = 0;
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static bool first_pos_edge = true;
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TaskHandle_t task_to_notify = (TaskHandle_t)user_data;
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BaseType_t high_task_wakeup = pdFALSE;
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static pwm_raw_data_t raw_data = {0};
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if (edata->cap_edge == MCPWM_CAP_EDGE_POS) {
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if (first_pos_edge) {
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// First positive edge - just record the timestamp
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period_start = edata->cap_value;
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last_pos_edge = edata->cap_value;
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first_pos_edge = false;
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} else {
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// Calculate period (time between two positive edges) - only integer arithmetic in ISR
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raw_data.period_ticks = edata->cap_value - period_start;
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raw_data.high_time_ticks = last_neg_edge - last_pos_edge;
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// Update for next cycle
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period_start = edata->cap_value;
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last_pos_edge = edata->cap_value;
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// Notify the task with raw tick data - no floating point in ISR
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xTaskNotifyFromISR(task_to_notify, (uint32_t)&raw_data, eSetValueWithOverwrite, &high_task_wakeup);
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}
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} else {
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// Negative edge - record the timestamp
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last_neg_edge = edata->cap_value;
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}
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return high_task_wakeup == pdTRUE;
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}
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void app_main(void)
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{
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ESP_LOGI(TAG, "PWM Frequency and Duty Cycle Measurement Example");
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ESP_LOGI(TAG, "Connect PWM signal to GPIO %d", CONFIG_PWM_CAPTURE_IO);
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ESP_LOGI(TAG, "Install capture timer");
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mcpwm_cap_timer_handle_t cap_timer = NULL;
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mcpwm_capture_timer_config_t cap_conf = {
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.clk_src = MCPWM_CAPTURE_CLK_SRC_DEFAULT,
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.group_id = 0,
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};
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ESP_ERROR_CHECK(mcpwm_new_capture_timer(&cap_conf, &cap_timer));
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ESP_LOGI(TAG, "Install capture channel");
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mcpwm_cap_channel_handle_t cap_chan = NULL;
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mcpwm_capture_channel_config_t cap_ch_conf = {
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.gpio_num = CONFIG_PWM_CAPTURE_IO,
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.prescale = 1,
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// capture on both edges to measure period and duty cycle
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.flags.neg_edge = true,
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.flags.pos_edge = true,
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};
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ESP_ERROR_CHECK(mcpwm_new_capture_channel(cap_timer, &cap_ch_conf, &cap_chan));
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// pull up the GPIO internally
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ESP_ERROR_CHECK(gpio_set_pull_mode(CONFIG_PWM_CAPTURE_IO, GPIO_PULLUP_ONLY));
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ESP_LOGI(TAG, "Register capture callback");
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TaskHandle_t cur_task = xTaskGetCurrentTaskHandle();
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mcpwm_capture_event_callbacks_t cbs = {
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.on_cap = pwm_measure_callback,
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};
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ESP_ERROR_CHECK(mcpwm_capture_channel_register_event_callbacks(cap_chan, &cbs, cur_task));
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ESP_LOGI(TAG, "Enable capture channel");
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ESP_ERROR_CHECK(mcpwm_capture_channel_enable(cap_chan));
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ESP_LOGI(TAG, "Enable and start capture timer");
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ESP_ERROR_CHECK(mcpwm_capture_timer_enable(cap_timer));
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ESP_ERROR_CHECK(mcpwm_capture_timer_start(cap_timer));
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ESP_LOGI(TAG, "Starting PWM measurement...");
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ESP_LOGI(TAG, "Waiting for PWM signal on GPIO %d", CONFIG_PWM_CAPTURE_IO);
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uint32_t notification_value;
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while (1) {
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// wait for PWM measurement data
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if (xTaskNotifyWait(0x00, ULONG_MAX, &notification_value, pdMS_TO_TICKS(2000)) == pdTRUE) {
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pwm_raw_data_t *raw_data = (pwm_raw_data_t *)notification_value;
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// Check for valid measurement (period > 0)
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if (raw_data->period_ticks > 0) {
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// Calculate frequency and duty cycle in main task (floating point operations)
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float period_us = raw_data->period_ticks * (1000000.0 / esp_clk_apb_freq());
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float frequency_hz = 1000000.0 / period_us;
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float duty_cycle_percent = (float)raw_data->high_time_ticks / raw_data->period_ticks * 100.0;
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float high_time_us = raw_data->high_time_ticks * (1000000.0 / esp_clk_apb_freq());
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// Check for reasonable frequency range
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if (frequency_hz > 0 && frequency_hz < 1000000) {
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ESP_LOGI(TAG, "========================================");
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ESP_LOGI(TAG, "PWM Measurement:");
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ESP_LOGI(TAG, " Frequency: %.2f Hz", frequency_hz);
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ESP_LOGI(TAG, " Duty Cycle: %.2f%%", duty_cycle_percent);
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ESP_LOGI(TAG, " Period: %.2f us", period_us);
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ESP_LOGI(TAG, " High Time: %.2f us", high_time_us);
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ESP_LOGI(TAG, "========================================");
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} else {
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ESP_LOGW(TAG, "Invalid frequency calculated: %.2f Hz", frequency_hz);
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}
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} else {
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ESP_LOGW(TAG, "Invalid PWM measurement received (period_ticks = %u)", raw_data->period_ticks);
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}
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} else {
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ESP_LOGW(TAG, "No PWM signal detected on GPIO %d", CONFIG_PWM_CAPTURE_IO);
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}
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vTaskDelay(pdMS_TO_TICKS(1000));
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}
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}

‎examples/peripherals/pwm/pwm_info_clac/sdkconfig.defaults‎

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# This file was generated using idf.py save-defconfig. It can be edited manually.
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# Espressif IoT Development Framework (ESP-IDF) 5.5.1 Project Minimal Configuration
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#
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CONFIG_ESP_DEFAULT_CPU_FREQ_MHZ_240=y
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CONFIG_FREERTOS_HZ=1000

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