mcpwm_capture_hc_sr04 sample
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Outline
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "esp_log.h"
#include "esp_private/esp_clk.h"
#include "driver/mcpwm_cap.h"
#include "driver/gpio.h"
TAG
#define HC_SR04_TRIG_GPIO
#define HC_SR04_ECHO_GPIO
hc_sr04_echo_callback(mcpwm_cap_channel_handle_t, const mcpwm_capture_event_data_t *, void *)
gen_trig_output()
app_main()
Files
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SourceVuESP-IDF Framework and Examplesmcpwm_capture_hc_sr04 samplemain/mcpwm_capture_hc_sr04.c
 
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/* * SPDX-FileCopyrightText: 2021-2022 Espressif Systems (Shanghai) CO LTD * * SPDX-License-Identifier: Unlicense OR CC0-1.0 *//* ... */ #include "freertos/FreeRTOS.h" #include "freertos/task.h" #include "esp_log.h" #include "esp_private/esp_clk.h" #include "driver/mcpwm_cap.h" #include "driver/gpio.h"6 includes const static char *TAG = "example"; //////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// //////////////////// Please update the following configuration according to your board spec //////////////////////////// //////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// #define HC_SR04_TRIG_GPIO 0 #define HC_SR04_ECHO_GPIO 2 static bool hc_sr04_echo_callback(mcpwm_cap_channel_handle_t cap_chan, const mcpwm_capture_event_data_t *edata, void *user_data) { static uint32_t cap_val_begin_of_sample = 0; static uint32_t cap_val_end_of_sample = 0; TaskHandle_t task_to_notify = (TaskHandle_t)user_data; BaseType_t high_task_wakeup = pdFALSE; //calculate the interval in the ISR, //so that the interval will be always correct even when capture_queue is not handled in time and overflow. if (edata->cap_edge == MCPWM_CAP_EDGE_POS) { // store the timestamp when pos edge is detected cap_val_begin_of_sample = edata->cap_value; cap_val_end_of_sample = cap_val_begin_of_sample; }{...} else { cap_val_end_of_sample = edata->cap_value; uint32_t tof_ticks = cap_val_end_of_sample - cap_val_begin_of_sample; // notify the task to calculate the distance xTaskNotifyFromISR(task_to_notify, tof_ticks, eSetValueWithOverwrite, &high_task_wakeup); }{...} return high_task_wakeup == pdTRUE; }{ ... } /** * @brief generate single pulse on Trig pin to start a new sample *//* ... */ static void gen_trig_output(void) { gpio_set_level(HC_SR04_TRIG_GPIO, 1); // set high esp_rom_delay_us(10); gpio_set_level(HC_SR04_TRIG_GPIO, 0); // set low }{ ... } void app_main(void) { ESP_LOGI(TAG, "Install capture timer"); mcpwm_cap_timer_handle_t cap_timer = NULL; mcpwm_capture_timer_config_t cap_conf = { .clk_src = MCPWM_CAPTURE_CLK_SRC_DEFAULT, .group_id = 0, }{...}; ESP_ERROR_CHECK(mcpwm_new_capture_timer(&cap_conf, &cap_timer)); ESP_LOGI(TAG, "Install capture channel"); mcpwm_cap_channel_handle_t cap_chan = NULL; mcpwm_capture_channel_config_t cap_ch_conf = { .gpio_num = HC_SR04_ECHO_GPIO, .prescale = 1, // capture on both edge .flags.neg_edge = true, .flags.pos_edge = true, // pull up internally .flags.pull_up = true, }{...}; ESP_ERROR_CHECK(mcpwm_new_capture_channel(cap_timer, &cap_ch_conf, &cap_chan)); ESP_LOGI(TAG, "Register capture callback"); TaskHandle_t cur_task = xTaskGetCurrentTaskHandle(); mcpwm_capture_event_callbacks_t cbs = { .on_cap = hc_sr04_echo_callback, }{...}; ESP_ERROR_CHECK(mcpwm_capture_channel_register_event_callbacks(cap_chan, &cbs, cur_task)); ESP_LOGI(TAG, "Enable capture channel"); ESP_ERROR_CHECK(mcpwm_capture_channel_enable(cap_chan)); ESP_LOGI(TAG, "Configure Trig pin"); gpio_config_t io_conf = { .mode = GPIO_MODE_OUTPUT, .pin_bit_mask = 1ULL << HC_SR04_TRIG_GPIO, }{...}; ESP_ERROR_CHECK(gpio_config(&io_conf)); // drive low by default ESP_ERROR_CHECK(gpio_set_level(HC_SR04_TRIG_GPIO, 0)); ESP_LOGI(TAG, "Enable and start capture timer"); ESP_ERROR_CHECK(mcpwm_capture_timer_enable(cap_timer)); ESP_ERROR_CHECK(mcpwm_capture_timer_start(cap_timer)); uint32_t tof_ticks; while (1) { // trigger the sensor to start a new sample gen_trig_output(); // wait for echo done signal if (xTaskNotifyWait(0x00, ULONG_MAX, &tof_ticks, pdMS_TO_TICKS(1000)) == pdTRUE) { float pulse_width_us = tof_ticks * (1000000.0 / esp_clk_apb_freq()); if (pulse_width_us > 35000) { // out of range continue; }{...} // convert the pulse width into measure distance float distance = (float) pulse_width_us / 58; ESP_LOGI(TAG, "Measured distance: %.2fcm", distance); }{...} vTaskDelay(pdMS_TO_TICKS(500)); }{...} }{ ... }
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