esp-idf/examples/peripherals/i2s/i2s_basic/main/i2s_example_main.c

/*
 * SPDX-FileCopyrightText: 2021-2022 Espressif Systems (Shanghai) CO LTD
 *
 * SPDX-License-Identifier: Unlicense OR CC0-1.0
 */
/*  I2S Example
 *  This example code will output 100Hz sine wave and triangle wave to 2-channel of I2S driver
 *  Every 5 seconds, it will change bits_per_sample [16, 24, 32] for i2s data
 */
#include <stdio.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "driver/i2s.h"
#include "driver/gpio.h"
#include "esp_system.h"
#include "esp_log.h"
#include <math.h>


#define SAMPLE_RATE     (36000)
#define I2S_NUM         (0)
#define WAVE_FREQ_HZ    (100)
#define PI              (3.14159265)
#define I2S_BCK_IO      (GPIO_NUM_4)
#define I2S_WS_IO       (GPIO_NUM_5)
#define I2S_DO_IO       (GPIO_NUM_18)
#define I2S_DI_IO       (-1)

#define SAMPLE_PER_CYCLE (SAMPLE_RATE/WAVE_FREQ_HZ)

static const char* TAG = "i2s_example";

static void setup_triangle_sine_waves(int bits)
{
    int *samples_data = malloc(((bits+8)/16)*SAMPLE_PER_CYCLE*4);
    unsigned int i, sample_val;
    double sin_float, triangle_float, triangle_step = (double) pow(2, bits) / SAMPLE_PER_CYCLE;
    size_t i2s_bytes_write = 0;

    printf("\r\nTest bits=%d free mem=%d, written data=%d\n", bits, esp_get_free_heap_size(), ((bits+8)/16)*SAMPLE_PER_CYCLE*4);

    triangle_float = -(pow(2, bits)/2 - 1);

    for(i = 0; i < SAMPLE_PER_CYCLE; i++) {
        sin_float = sin(i * 2 * PI / SAMPLE_PER_CYCLE);
        if(sin_float >= 0)
            triangle_float += triangle_step;
        else
            triangle_float -= triangle_step;

        sin_float *= (pow(2, bits)/2 - 1);

        if (bits == 16) {
            sample_val = 0;
            sample_val += (short)triangle_float;
            sample_val = sample_val << 16;
            sample_val += (short) sin_float;
            samples_data[i] = sample_val;
        } else if (bits == 24) { //1-bytes unused
            samples_data[i*2] = ((int) triangle_float) << 8;
            samples_data[i*2 + 1] = ((int) sin_float) << 8;
        } else {
            samples_data[i*2] = ((int) triangle_float);
            samples_data[i*2 + 1] = ((int) sin_float);
        }

    }
    ESP_LOGI(TAG, "set clock");
    i2s_set_clk(I2S_NUM, SAMPLE_RATE, bits, 2);
    //Using push
    // for(i = 0; i < SAMPLE_PER_CYCLE; i++) {
    //     if (bits == 16)
    //         i2s_push_sample(0, &samples_data[i], 100);
    //     else
    //         i2s_push_sample(0, &samples_data[i*2], 100);
    // }
    // or write
    ESP_LOGI(TAG, "write data");
    i2s_write(I2S_NUM, samples_data, ((bits+8)/16)*SAMPLE_PER_CYCLE*4, &i2s_bytes_write, 100);

    free(samples_data);
}

void app_main(void)
{
    //for 36Khz sample rates, we create 100Hz sine wave, every cycle need 36000/100 = 360 samples (4-bytes or 8-bytes each sample)
    //depend on bits_per_sample
    //using 6 buffers, we need 60-samples per buffer
    //if 2-channels, 16-bit each channel, total buffer is 360*4 = 1440 bytes
    //if 2-channels, 24/32-bit each channel, total buffer is 360*8 = 2880 bytes
    i2s_config_t i2s_config = {
        .mode = I2S_MODE_MASTER | I2S_MODE_TX,
        .sample_rate = SAMPLE_RATE,
        .bits_per_sample = I2S_BITS_PER_SAMPLE_16BIT,
        .channel_format = I2S_CHANNEL_FMT_RIGHT_LEFT,
        .communication_format = I2S_COMM_FORMAT_STAND_MSB,
        .dma_desc_num = 6,
        .dma_frame_num = 60,
        .use_apll = false,
        .intr_alloc_flags = ESP_INTR_FLAG_LEVEL1                                //Interrupt level 1
    };
    i2s_pin_config_t pin_config = {
        .mck_io_num = I2S_PIN_NO_CHANGE,
        .bck_io_num = I2S_BCK_IO,
        .ws_io_num = I2S_WS_IO,
        .data_out_num = I2S_DO_IO,
        .data_in_num = I2S_DI_IO                                               //Not used
    };
    i2s_driver_install(I2S_NUM, &i2s_config, 0, NULL);
    i2s_set_pin(I2S_NUM, &pin_config);

    int test_bits = 16;
    while (1) {
        setup_triangle_sine_waves(test_bits);
        vTaskDelay(5000/portTICK_PERIOD_MS);
        test_bits += 8;
        if(test_bits > 32)
            test_bits = 16;

    }

}