test.c

#include <string.h>
#include <sys/unistd.h>
#include <sys/stat.h>
#include <driver/i2s.h>

#define SAMPLE_RATE 325000
#define BITS_PER_SAMPLE 16

uint8_t buffer[1024];

void app_main(void)
{
    //Set up I2S
    i2s_config_t i2s_config = {
        .mode = (i2s_mode_t)(I2S_MODE_SLAVE | I2S_MODE_RX),
        .sample_rate = SAMPLE_RATE,
        .bits_per_sample = BITS_PER_SAMPLE,
        .channel_format = I2S_CHANNEL_FMT_RIGHT_LEFT,
        .communication_format = I2S_COMM_FORMAT_STAND_I2S,
        .intr_alloc_flags = ESP_INTR_FLAG_LEVEL1,
        .dma_buf_count = 16,
        .dma_buf_len = 1024,
        .use_apll = true,
        .tx_desc_auto_clear = false,
        .fixed_mclk = 41600000, //20800000?
        .mclk_multiple = I2S_MCLK_MULTIPLE_DEFAULT
    };
    i2s_driver_install(I2S_NUM_0, &i2s_config, 0, NULL);

    //Set up pins
    i2s_pin_config_t pin_config = {
        .bck_io_num = 18,
        .ws_io_num = 5,
        .data_out_num = I2S_PIN_NO_CHANGE,
        .data_in_num = 23
    };
    i2s_set_pin(I2S_NUM_0, &pin_config);

    //Set up ports
    int64_t targetByteRate = SAMPLE_RATE * (BITS_PER_SAMPLE / 8) * 2;

    //Enter loop
    size_t read;
    size_t totalRead = 0;
    int64_t start = esp_timer_get_time();
    int64_t end = esp_timer_get_time();
    while (true) {
        //Read
        i2s_read(I2S_NUM_0, buffer, sizeof(buffer), &read, 300);
        totalRead += read;
        if (read == 0)
            printf("WARN: No data is being read from I2S!\n");

        //Check if we've reached the end
        end = esp_timer_get_time();
        if ((end - start) > 5000000)
            break;
    }

    //Print info
    double speed = totalRead / ((end - start) / 1000000.0);
    printf("FINISHED WRITING. Read %i bytes at %f bytes/sec (%f%% of target)\n", totalRead, (float)speed, (float)((speed / targetByteRate) * 100.0));
}