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

/* I2S Example
    
    This example code will output 100Hz sine wave and triangle wave to 2-channel of I2S driver

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

    Unless required by applicable law or agreed to in writing, this
    software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
    CONDITIONS OF ANY KIND, either express or implied.
*/
#include <stdio.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "driver/i2s.h"
#include <math.h>


#define SAMPLE_RATE     (36000)
#define I2S_NUM         (0)
#define WAVE_FREQ_HZ    (100)
#define PI 3.14159265

#define SAMPLE_PER_CYCLE (SAMPLE_RATE/WAVE_FREQ_HZ)

void app_main()
{
    unsigned int i, sample_val;
    float sin_float, triangle_float, triangle_step = 65536.0 / SAMPLE_PER_CYCLE;
    //for 36Khz sample rates, we create 100Hz sine wave, every cycle need 36000/100 = 360 samples (4-bytes each sample)
    //using 6 buffers, we need 60-samples per buffer
    //2-channels, 16-bit each channel, total buffer is 360*4 = 1440 bytes
    i2s_config_t i2s_config = {
        .mode = I2S_MODE_MASTER | I2S_MODE_TX,                                  // Only TX
        .sample_rate = SAMPLE_RATE,
        .bits_per_sample = 16,                                                  //16-bit per channel
        .channel_format = I2S_CHANNEL_FMT_RIGHT_LEFT,                           //2-channels
        .communication_format = I2S_COMM_FORMAT_I2S | I2S_COMM_FORMAT_I2S_MSB,
        .dma_buf_count = 6,
        .dma_buf_len = 60,                                                      //
        .intr_alloc_flags = ESP_INTR_FLAG_LEVEL1                                //Interrupt level 1
    };
    i2s_pin_config_t pin_config = {
        .bck_io_num = 26,
        .ws_io_num = 25,
        .data_out_num = 22,
        .data_in_num = -1                                                       //Not used
    };

    i2s_driver_install(I2S_NUM, &i2s_config, 0, NULL);
    i2s_set_pin(I2S_NUM, &pin_config);

    triangle_float = -32767;

    for(i = 0; i < SAMPLE_PER_CYCLE; i++) {
        sin_float = sin(i * PI / 180.0);
        if(sin_float >= 0)
            triangle_float += triangle_step;
        else
            triangle_float -= triangle_step;
        sin_float *= 32767;

        sample_val = 0;
        sample_val += (short)triangle_float;
        sample_val = sample_val << 16;
        sample_val += (short) sin_float;
 
        i2s_push_sample(I2S_NUM, (char *)&sample_val, portMAX_DELAY);
    }
}