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Code: Select all

I (5332) i2s_cb: Min interval  (us): 0
I (5332) i2s_cb: Max interval  (us): 4610
I (5332) i2s_cb: Avg interval  (us): 2451
I (6282) i2s_cb: Min interval  (us): 0
I (6282) i2s_cb: Max interval  (us): 4609
I (6282) i2s_cb: Avg interval  (us): 2464
I (7222) i2s_cb: Min interval  (us): 0
I (7222) i2s_cb: Max interval  (us): 4609
I (7222) i2s_cb: Avg interval  (us): 2464
I (8172) i2s_cb: Min interval  (us): 0
I (8172) i2s_cb: Max interval  (us): 4610
I (8172) i2s_cb: Avg interval  (us): 2451

Code: Select all

static bool IRAM_ATTR sent_callback(i2s_chan_handle_t handle,
                                    i2s_event_data_t* event,
                                    void* user_ctx)
{
    int64_t* p_ts = (int64_t*)(user_ctx);
    *p_ts         = (s_config.timestamp_fn)(); // This points to the esp_timer_get_time function...
    return false;
}

static void i2s_pdm_tx_task(void* args)
{
    const int buf_size_bytes =
        s_config.buffer_size * (s_config.stereo ? 2 : 1) * sizeof(int16_t);
    int16_t* w_buf = (int16_t*)calloc(1, buf_size_bytes);
    assert(w_buf);
    i2s_chan_handle_t tx_chan =
        i2s_init_pdm_tx(s_config.sample_rate, s_config.stereo);

    size_t w_bytes = 0;
    int64_t timestamp;
    int n                           = 0;
    i2s_event_callbacks_t callbacks = {NULL};
    callbacks.on_sent               = sent_callback;
    ESP_ERROR_CHECK(
        i2s_channel_register_event_callback(tx_chan, &callbacks, &timestamp));

    // Preload first data
    (s_config.i2s_callback_fn)(
        s_config.args, timestamp, w_buf, s_config.buffer_size);
    ESP_ERROR_CHECK(
        i2s_channel_preload_data(tx_chan, w_buf, buf_size_bytes, &w_bytes));

    ESP_ERROR_CHECK(i2s_channel_enable(tx_chan));

    while (1) {
        // Call the audio callback function
        (s_config.i2s_callback_fn)(
            s_config.args, timestamp, w_buf, s_config.buffer_size);
        // Write buffer to I2S DMA
        if (i2s_channel_write(tx_chan, w_buf, buf_size_bytes, &w_bytes, 1000) !=
                ESP_OK ||
            w_bytes != buf_size_bytes) {
            ESP_LOGE(TAG, "Write Task: i2s write failed");
            break;
        }
    }
    free(w_buf);
    vTaskDelete(NULL);
}

Code: Select all

esp_err_t i2s_alloc_dma_desc(i2s_chan_handle_t handle, uint32_t num, uint32_t bufsize)
{
    I2S_NULL_POINTER_CHECK(TAG, handle);
    esp_err_t ret = ESP_OK;
    ESP_RETURN_ON_FALSE(bufsize <= I2S_DMA_BUFFER_MAX_SIZE, ESP_ERR_INVALID_ARG, TAG, "dma buffer can't be bigger than %d", I2S_DMA_BUFFER_MAX_SIZE);
    num = 2;
    bufsize = 256;
    handle->dma.desc_num = num;
    handle->dma.buf_size = bufsize;
    printf("-----------> num=%lu, bufsize=%lu\n", num, bufsize);
    ...

Code: Select all

I (3402) i2s_cb: Min interval  (us): 2457
I (3402) i2s_cb: Max interval  (us): 2458
I (3402) i2s_cb: Avg interval  (us): 2457

Code: Select all

static i2s_chan_handle_t i2s_init_pdm_tx(int sample_rate, bool stereo)
{
    i2s_chan_handle_t tx_chan;  // I2S tx channel handler
    /* Setp 1: Determine the I2S channel configuration and allocate TX channel
     * only The default configuration can be generated by the helper macro, it
     * only requires the I2S controller id and I2S role, but note that PDM
     * channel can only be registered on I2S_NUM_0 */
    i2s_chan_config_t tx_chan_cfg =
        I2S_CHANNEL_DEFAULT_CONFIG(I2S_NUM_AUTO, I2S_ROLE_MASTER);
    tx_chan_cfg.auto_clear    = true;
    tx_chan_cfg.intr_priority = 7;
    ESP_ERROR_CHECK(i2s_new_channel(&tx_chan_cfg, &tx_chan, NULL));

    /* Step 2: Setting the configurations of PDM TX mode and initialize the TX
     * channel The slot configuration and clock configuration can be generated
     * by the macros These two helper macros is defined in 'i2s_pdm.h' which can
     * only be used in PDM TX mode. They can help to specify the slot and clock
     * configurations for initialization or re-configuring */
    i2s_pdm_tx_config_t pdm_tx_cfg = {
        .clk_cfg = I2S_PDM_TX_CLK_DEFAULT_CONFIG(sample_rate),
        /* The data bit-width of PDM mode is fixed to 16 */
        .slot_cfg = I2S_PDM_TX_SLOT_DEFAULT_CONFIG(
            I2S_DATA_BIT_WIDTH_16BIT,
            (stereo ? I2S_SLOT_MODE_STEREO : I2S_SLOT_MODE_MONO)),
        .gpio_cfg =
            {
                .clk  = PDM_TX_CLK_IO,
                .dout = PDM_TX_DOUT_IO,
                .invert_flags =
                    {
                        .clk_inv = false,
                    },
            },
    };
    pdm_tx_cfg.slot_cfg.hp_en = false;
    ESP_ERROR_CHECK(i2s_channel_init_pdm_tx_mode(tx_chan, &pdm_tx_cfg));

    return tx_chan;
}

Code: Select all

static void i2s_callback(void* args, int64_t timestamp, void* data, int size)
{
    sine_t* p = (sine_t*)(args);
    if (p->calculations < 10) {
        if (p->counter == 0) {
            p->first_time     = timestamp;
            p->min_interval   = INT64_MAX;
            p->max_interval   = 0;
            p->total_interval = 0;
        } else if (p->counter > 0) {
            // Calculate interval since the last message
            int64_t interval = timestamp - p->last_time;

            if (interval < p->min_interval)
                p->min_interval = interval;
            if (interval > p->max_interval)
                p->max_interval = interval;
            p->total_interval += interval;
        }
        p->last_time = timestamp;
        p->counter++;
        if (p->counter * size >= 48000) {
            int intervals_count  = p->counter - 1;
            int64_t avg_interval = p->total_interval / intervals_count;
            ESP_LOGI("i2s_cb", "Min interval  (us): %" PRId64, p->min_interval);
            ESP_LOGI("i2s_cb", "Max interval  (us): %" PRId64, p->max_interval);
            ESP_LOGI("i2s_cb", "Avg interval  (us): %" PRId64, avg_interval);
            p->calculations++;
        }
    }

    const float factor = 6.2831853072f / p->periodicity;
    int16_t* buf       = (int16_t*)(data);
    for (int i = 0; i < size; ++i) {
        const float v = sinf(p->pos * factor) * 16383.0f;
        buf[i]        = (int16_t)(v);
        p->pos        = (p->pos + 1) % p->periodicity;
    }
}

static int64_t IRAM_ATTR i2s_timestamp_callback(void)
{
    return esp_timer_get_time();
}