esp-idf/examples/peripherals/wave_gen/main/wave_gen_example_main.c

/*  Wave Generator Example

    This example code is in the Public Domain (or CC0 licensed, at your option.)

    DAC output channel, waveform, wave frequency can be customized in menuconfig.
    If any questions about this example or more information is needed, please read README.md before your start.
*/
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <assert.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/queue.h"
#include "driver/gpio.h"
#include "driver/dac.h"
#include "driver/timer.h"
#include "esp_log.h"

/*  The timer ISR has an execution time of 5.5 micro-seconds(us).
    Therefore, a timer period less than 5.5 us will cause trigger the interrupt watchdog.
    7 us is a safe interval that will not trigger the watchdog. No need to customize it.
*/

#define WITH_RELOAD            1
#define TIMER_INTR_US          7                                    // Execution time of each ISR interval in micro-seconds
#define TIMER_DIVIDER          16
#define POINT_ARR_LEN          200                                  // Length of points array
#define AMP_DAC                255                                  // Amplitude of DAC voltage. If it's more than 256 will causes dac_output_voltage() output 0.
#define VDD                    3300                                 // VDD is 3.3V, 3300mV
#define CONST_PERIOD_2_PI      6.2832
#define SEC_TO_MICRO_SEC(x)    ((x) / 1000 / 1000)                  // Convert second to micro-second
#define UNUSED_PARAM           __attribute__((unused))              // A const period parameter which equals 2 * pai, used to calculate raw dac output value.
#define TIMER_TICKS            (TIMER_BASE_CLK / TIMER_DIVIDER)     // TIMER_BASE_CLK = APB_CLK = 80MHz
#define ALARM_VAL_US           SEC_TO_MICRO_SEC(TIMER_INTR_US * TIMER_TICKS)     // Alarm value in micro-seconds
#define OUTPUT_POINT_NUM       (int)(1000000 / (TIMER_INTR_US * FREQ) + 0.5)     // The number of output wave points.

#define DAC_CHAN               CONFIG_EXAMPLE_DAC_CHANNEL           // DAC_CHANNEL_1 (GPIO25) by default
#define FREQ                   CONFIG_EXAMPLE_WAVE_FREQUENCY        // 3kHz by default

_Static_assert(OUTPUT_POINT_NUM <= POINT_ARR_LEN, "The CONFIG_EXAMPLE_WAVE_FREQUENCY is too low and using too long buffer.");

static int raw_val[POINT_ARR_LEN];                      // Used to store raw values
static int volt_val[POINT_ARR_LEN];                    // Used to store voltage values(in mV)
static const char *TAG = "wave_gen";

static int g_index = 0;

/* Timer interrupt service routine */
static void IRAM_ATTR timer0_ISR(void *ptr)
{
    timer_group_clr_intr_status_in_isr(TIMER_GROUP_0, TIMER_0);
    timer_group_enable_alarm_in_isr(TIMER_GROUP_0, TIMER_0);

    int *head = (int*)ptr;

    /* DAC output ISR has an execution time of 4.4 us*/
    if (g_index >= OUTPUT_POINT_NUM) g_index = 0;
    dac_output_voltage(DAC_CHAN, *(head + g_index));
    g_index++;
}

/* Timer group0 TIMER_0 initialization */
static void example_timer_init(int timer_idx, bool auto_reload)
{
    esp_err_t ret;
    timer_config_t config = {
        .divider = TIMER_DIVIDER,
        .counter_dir = TIMER_COUNT_UP,
        .counter_en = TIMER_PAUSE,
        .alarm_en = TIMER_ALARM_EN,
        .intr_type = TIMER_INTR_LEVEL,
        .auto_reload = auto_reload,
    };

    ret = timer_init(TIMER_GROUP_0, timer_idx, &config);
    ESP_ERROR_CHECK(ret);
    ret = timer_set_counter_value(TIMER_GROUP_0, timer_idx, 0x00000000ULL);
    ESP_ERROR_CHECK(ret);
    ret = timer_set_alarm_value(TIMER_GROUP_0, timer_idx, ALARM_VAL_US);
    ESP_ERROR_CHECK(ret);
    ret = timer_enable_intr(TIMER_GROUP_0, TIMER_0);
    ESP_ERROR_CHECK(ret);
    /* Register an ISR handler */
    timer_isr_register(TIMER_GROUP_0, timer_idx, timer0_ISR, (void *)raw_val, 0, NULL);
}

 static void prepare_data(int pnt_num)
{
    timer_pause(TIMER_GROUP_0, TIMER_0);
    for (int i = 0; i < pnt_num; i ++) {
        #ifdef CONFIG_EXAMPLE_WAVEFORM_SINE
            raw_val[i] = (int)((sin( i * CONST_PERIOD_2_PI / pnt_num) + 1) * (double)(AMP_DAC)/2 + 0.5);
        #elif CONFIG_EXAMPLE_WAVEFORM_TRIANGLE
            raw_val[i] = (i > (pnt_num/2)) ? (2 * AMP_DAC * (pnt_num - i) / pnt_num) : (2 * AMP_DAC * i / pnt_num);
        #elif CONFIG_EXAMPLE_WAVEFORM_SAWTOOTH
            raw_val[i] = (i == pnt_num) ? 0 : (i * AMP_DAC / pnt_num);
        #elif CONFIG_EXAMPLE_WAVEFORM_SQUARE
            raw_val[i] = (i < (pnt_num/2)) ? AMP_DAC : 0;
        #endif
        volt_val[i] = (int)(VDD * raw_val[i] / (float)AMP_DAC);
    }
    timer_start(TIMER_GROUP_0, TIMER_0);
}

static void log_info(void)
{
    ESP_LOGI(TAG, "DAC output channel: %d", DAC_CHAN);
    if (DAC_CHAN == DAC_CHANNEL_1) {
        ESP_LOGI(TAG, "GPIO:%d", GPIO_NUM_25);
    } else {
        ESP_LOGI(TAG, "GPIO:%d", GPIO_NUM_26);
    }
    #ifdef CONFIG_EXAMPLE_WAVEFORM_SINE
        ESP_LOGI(TAG, "Waveform: SINE");
    #elif CONFIG_EXAMPLE_WAVEFORM_TRIANGLE
        ESP_LOGI(TAG, "Waveform: TRIANGLE");
    #elif CONFIG_EXAMPLE_WAVEFORM_SAWTOOTH
        ESP_LOGI(TAG, "Waveform: SAWTOOTH");
    #elif CONFIG_EXAMPLE_WAVEFORM_SQUARE
        ESP_LOGI(TAG, "Waveform: SQUARE");
    #endif

    ESP_LOGI(TAG, "Frequency(Hz): %d", FREQ);
    ESP_LOGI(TAG, "Output points num: %d\n", OUTPUT_POINT_NUM);
}

void app_main(void)
{
    esp_err_t ret;
    example_timer_init(TIMER_0, WITH_RELOAD);

    ret = dac_output_enable(DAC_CHAN);
    ESP_ERROR_CHECK(ret);

    log_info();
    g_index = 0;
    prepare_data(OUTPUT_POINT_NUM);

    while(1) {
        vTaskDelay(10);
        #if CONFIG_EXAMPLE_LOG_VOLTAGE
            if (g_index < OUTPUT_POINT_NUM) {
                ESP_LOGI(TAG, "Output voltage(mV): %d", volt_val[g_index]);
                ESP_LOGD(TAG, "g_index: %d\n", g_index);
            }
        #endif
    }
}