esp32_sd_faster.c

#include <string.h>
#include <sys/unistd.h>
#include <sys/stat.h>
#include "esp_vfs_fat.h"
#include "sdmmc_cmd.h"
#include "driver/sdmmc_host.h"
#include <driver/i2s.h>

static const char *TAG = "example";

// General
#define MOUNT_POINT "/sdcard"
#define MICROSECONDS_PER_SECOND 1000000
#define SECTOR_COUNT 64
//#define IQ_MODE

#ifdef IQ_MODE

/* IQ Baseband Mode (ground=red, 23=orange, 18=green, 5=blue) */
#define SAMPLE_RATE (325000 * 2)
#define BITS_PER_SAMPLE 16
#define FIXED_MCLK 20800000
#define COMM_FMT I2S_COMM_FORMAT_STAND_I2S
#define USE_APLL true
/* END IQ Baseband Mode */

#else

/* HD Mode (ground=blue, 23=orange, 18=yellow, 5=green) */
#define SAMPLE_RATE 44100
#define BITS_PER_SAMPLE 32
#define FIXED_MCLK 0
#define COMM_FMT I2S_COMM_FORMAT_STAND_I2S
#define USE_APLL false
/* END HD Mode */

#endif

int64_t configure_port(i2s_port_t port, int dmaChunkSize) {
    //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 = COMM_FMT,
        .intr_alloc_flags = ESP_INTR_FLAG_LEVEL1,  // Interrupt level 1, default 0
        .dma_buf_count = 32,
        .dma_buf_len = dmaChunkSize,
        .use_apll = USE_APLL,
        .tx_desc_auto_clear = false,
        .fixed_mclk = FIXED_MCLK,
        .mclk_multiple = I2S_MCLK_MULTIPLE_DEFAULT
    };
    i2s_driver_install(port, &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(port, &pin_config);

    //Calculate data rate
    return SAMPLE_RATE * (BITS_PER_SAMPLE / 8) * 2;
}

void app_main(void)
{
    //Initialize SD card driver
    if (sdmmc_host_init() != ESP_OK) {
        printf("Failed to initialize SD card driver.\n");
        return;
    }

    //Initialize slot
    sdmmc_slot_config_t slot = SDMMC_SLOT_CONFIG_DEFAULT();
    slot.width = 4;
    slot.flags |= SDMMC_SLOT_FLAG_INTERNAL_PULLUP;
    if (sdmmc_host_init_slot(1, &slot) != ESP_OK) {
        printf("Failed to initialize SD card slot.\n");
        return;
    }

    //Open card
    printf("Opening SD card...\n");
    sdmmc_host_t host = SDMMC_HOST_DEFAULT();
    host.max_freq_khz = SDMMC_FREQ_HIGHSPEED;
    sdmmc_card_t card;
    if (sdmmc_card_init(&host, &card) != ESP_OK) {
        printf("Failed to open SD card! Rebooting...\n");
        vTaskDelay(1000 / portTICK_PERIOD_MS);
        esp_restart();
    }

    //Get info
    sdmmc_card_print_info(stdout, &card);
    printf("Sector size: %i\n", card.csd.sector_size);

    //Set up ports
    int64_t targetByteRate = configure_port(I2S_NUM_0, card.csd.sector_size);

    //Allocate sector buffer
    size_t bufferSize = SECTOR_COUNT * card.csd.sector_size;
    void* buffer = malloc(bufferSize);
    if (buffer == 0) {
        printf("Failed to allocate buffer!\n");
        return;
    }

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

        //Write
        end = esp_timer_get_time();
        if (sdmmc_write_sectors(&card, buffer, sector, SECTOR_COUNT) != ESP_OK) {
            printf("Failed to write sectors to SD card! Aborting...\n");
            break;
        }

        //Advance
        sector += SECTOR_COUNT;
    }

    //Print info
    int64_t written = sector * card.csd.sector_size;
    double speed = written / ((end - start) / 1000000.0);
    ESP_LOGI(TAG, "FINISHED WRITING. Wrote %i sectors (%lli bytes) at %f bytes/sec (%f%% of target)", sector, written, (float)speed, (float)((speed / targetByteRate) * 100.0));
}

(ps, there's a memory leak since I forgot to free the buffer)