sdm_dac sample
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Outline
#include <math.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "esp_log.h"
#include "driver/sdm.h"
#include "driver/gptimer.h"
#define MHZ
#define CONST_PI
#define EXAMPLE_SIGMA_DELTA_GPIO_NUM
#define EXAMPLE_OVER_SAMPLE_RATE
#define EXAMPLE_TIMER_RESOLUTION
#define EXAMPLE_CALLBACK_INTERVAL_US
#define EXAMPLE_ALARM_COUNT
#define EXAMPLE_SINE_WAVE_FREQ_HZ
#define EXAMPLE_SINE_WAVE_AMPLITUDE
#define EXAMPLE_SINE_WAVE_POINT_NUM
TAG
sine_wave
example_timer_callback(gptimer_handle_t, const gptimer_alarm_event_data_t *, void *)
example_init_gptimer(void *)
example_init_sdm()
app_main()
Files
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SourceVuESP-IDF Framework and Examplessdm_dac samplemain/sdm_dac_example_main.c
 
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/* * SPDX-FileCopyrightText: 2022-2023 Espressif Systems (Shanghai) CO LTD * * SPDX-License-Identifier: Unlicense OR CC0-1.0 *//* ... */ #include <math.h> #include "freertos/FreeRTOS.h" #include "freertos/task.h" #include "esp_log.h" #include "driver/sdm.h" #include "driver/gptimer.h"6 includes #define MHZ (1000000) #define CONST_PI (3.1416f) // Constant of PI, used for calculating the sine wave #define EXAMPLE_SIGMA_DELTA_GPIO_NUM (0) // Select GPIO_NUM_0 as the sigma-delta output pin #define EXAMPLE_OVER_SAMPLE_RATE (10 * MHZ) // 10 MHz over sample rate #define EXAMPLE_TIMER_RESOLUTION (1 * MHZ) // 1 MHz timer counting resolution #define EXAMPLE_CALLBACK_INTERVAL_US (100) // 100 us interval of each timer callback #define EXAMPLE_ALARM_COUNT (EXAMPLE_CALLBACK_INTERVAL_US * (EXAMPLE_TIMER_RESOLUTION / MHZ)) #define EXAMPLE_SINE_WAVE_FREQ_HZ (100) // 100 Hz sine wave, adjust this value to decide the sine wave frequency #define EXAMPLE_SINE_WAVE_AMPLITUDE (127.0f) // 1 ~ 127, adjust this value to decide the sine wave amplitude #define EXAMPLE_SINE_WAVE_POINT_NUM (MHZ / (EXAMPLE_CALLBACK_INTERVAL_US * EXAMPLE_SINE_WAVE_FREQ_HZ))10 defines ESP_STATIC_ASSERT(EXAMPLE_SINE_WAVE_POINT_NUM > 1, "Sine wave frequency is too high"); ESP_STATIC_ASSERT(EXAMPLE_CALLBACK_INTERVAL_US >= 7, "Timer callback interval is too short"); static const char *TAG = "sdm_dac"; static int8_t sine_wave[EXAMPLE_SINE_WAVE_POINT_NUM]; // Sine wave data buffer static bool IRAM_ATTR example_timer_callback(gptimer_handle_t timer, const gptimer_alarm_event_data_t *edata, void *user_ctx) { static uint32_t cnt = 0; sdm_channel_handle_t sdm_chan = (sdm_channel_handle_t)user_ctx; /* Set the pulse density */ sdm_channel_set_pulse_density(sdm_chan, sine_wave[cnt++]); /* Loop the sine wave data buffer */ if (cnt >= EXAMPLE_SINE_WAVE_POINT_NUM) { cnt = 0; }{...} return false; }{ ... } static gptimer_handle_t example_init_gptimer(void* args) { /* Allocate GPTimer handle */ gptimer_handle_t timer_handle; gptimer_config_t timer_cfg = { .clk_src = GPTIMER_CLK_SRC_DEFAULT, .direction = GPTIMER_COUNT_UP, .resolution_hz = EXAMPLE_TIMER_RESOLUTION, }{...}; ESP_ERROR_CHECK(gptimer_new_timer(&timer_cfg, &timer_handle)); ESP_LOGI(TAG, "Timer allocated with resolution %d Hz", EXAMPLE_TIMER_RESOLUTION); /* Set the timer alarm configuration */ gptimer_alarm_config_t alarm_cfg = { .alarm_count = EXAMPLE_ALARM_COUNT, .reload_count = 0, .flags.auto_reload_on_alarm = true, }{...}; ESP_ERROR_CHECK(gptimer_set_alarm_action(timer_handle, &alarm_cfg)); /* Register the alarm callback */ gptimer_event_callbacks_t cbs = { .on_alarm = example_timer_callback, }{...}; ESP_ERROR_CHECK(gptimer_register_event_callbacks(timer_handle, &cbs, args)); ESP_LOGI(TAG, "Timer callback registered, interval %d us", EXAMPLE_CALLBACK_INTERVAL_US); /* Clear the timer raw count value, make sure it'll count from 0 */ ESP_ERROR_CHECK(gptimer_set_raw_count(timer_handle, 0)); /* Enable the timer */ ESP_ERROR_CHECK(gptimer_enable(timer_handle)); ESP_LOGI(TAG, "Timer enabled"); return timer_handle; }{ ... } static sdm_channel_handle_t example_init_sdm(void) { /* Allocate sdm channel handle */ sdm_channel_handle_t sdm_chan = NULL; sdm_config_t config = { .clk_src = SDM_CLK_SRC_DEFAULT, .gpio_num = EXAMPLE_SIGMA_DELTA_GPIO_NUM, .sample_rate_hz = EXAMPLE_OVER_SAMPLE_RATE, }{...}; ESP_ERROR_CHECK(sdm_new_channel(&config, &sdm_chan)); /* Enable the sdm channel */ ESP_ERROR_CHECK(sdm_channel_enable(sdm_chan)); ESP_LOGI(TAG, "Sigma-delta output is attached to GPIO %d", EXAMPLE_SIGMA_DELTA_GPIO_NUM); return sdm_chan; }{ ... } void app_main(void) { /* Assign sine wave data */ for (int i = 0; i < EXAMPLE_SINE_WAVE_POINT_NUM; i++) { sine_wave[i] = (int8_t)((sin(2 * (float)i * CONST_PI / EXAMPLE_SINE_WAVE_POINT_NUM)) * EXAMPLE_SINE_WAVE_AMPLITUDE); }{...} /* Initialize sigma-delta modulation on the specific GPIO */ sdm_channel_handle_t sdm_chan = example_init_sdm(); /* Initialize GPTimer and register the timer alarm callback */ gptimer_handle_t timer_handle = example_init_gptimer(sdm_chan); /* Start the GPTimer */ ESP_LOGI(TAG, "Output start"); ESP_ERROR_CHECK(gptimer_start(timer_handle)); }{ ... }
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