machine_i2s.c

/*
 * This file is part of the MicroPython project, http://micropython.org/
 *
 * The MIT License (MIT)
 *
 * Copyright (c) 2021 Mike Teachman
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

// This file is never compiled standalone, it's included directly from
// extmod/machine_i2s.c via MICROPY_PY_MACHINE_I2S_INCLUDEFILE.

#include "py/mphal.h"

#include "driver/i2s.h"
#include "soc/i2s_reg.h"
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/queue.h"
#include "esp_task.h"

// Notes on this port's specific implementation of I2S:
// - a FreeRTOS task is created to implement the asynchronous background operations
// - a FreeRTOS queue is used to transfer the supplied buffer to the background task
// - all sample data transfers use DMA

#define I2S_TASK_PRIORITY        (ESP_TASK_PRIO_MIN + 1)
#define I2S_TASK_STACK_SIZE      (2048)

#define DMA_BUF_LEN_IN_I2S_FRAMES (256)

// The transform buffer is used with the readinto() method to bridge the opaque DMA memory on the ESP devices
// with the app buffer.  It facilitates audio sample transformations.  e.g.  32-bits samples to 16-bit samples.
// The size of 240 bytes is an engineering optimum that balances transfer performance with an acceptable use of heap space
#define SIZEOF_TRANSFORM_BUFFER_IN_BYTES (240)

typedef enum {
    I2S_TX_TRANSFER,
    I2S_RX_TRANSFER,
} direction_t;

typedef struct _non_blocking_descriptor_t {
    mp_buffer_info_t appbuf;
    mp_obj_t callback;
    direction_t direction;
} non_blocking_descriptor_t;

typedef struct _machine_i2s_obj_t {
    mp_obj_base_t base;
    i2s_port_t i2s_id;
    mp_hal_pin_obj_t sck;
    mp_hal_pin_obj_t ws;
    mp_hal_pin_obj_t sd;
    int8_t mode;
    i2s_bits_per_sample_t bits;
    format_t format;
    int32_t rate;
    int32_t ibuf;
    mp_obj_t callback_for_non_blocking;
    io_mode_t io_mode;
    uint8_t transform_buffer[SIZEOF_TRANSFORM_BUFFER_IN_BYTES];
    QueueHandle_t i2s_event_queue;
    QueueHandle_t non_blocking_mode_queue;
    TaskHandle_t non_blocking_mode_task;
} machine_i2s_obj_t;

STATIC mp_obj_t machine_i2s_deinit(mp_obj_t self_in);

// The frame map is used with the readinto() method to transform the audio sample data coming
// from DMA memory (32-bit stereo, with the L and R channels reversed) to the format specified
// in the I2S constructor.  e.g.  16-bit mono
STATIC const int8_t i2s_frame_map[NUM_I2S_USER_FORMATS][I2S_RX_FRAME_SIZE_IN_BYTES] = {
    { 6,  7, -1, -1, -1, -1, -1, -1 },  // Mono, 16-bits
    { 4,  5,  6,  7, -1, -1, -1, -1 },  // Mono, 32-bits
    { 6,  7,  2,  3, -1, -1, -1, -1 },  // Stereo, 16-bits
    { 4,  5,  6,  7,  0,  1,  2,  3 },  // Stereo, 32-bits
};

void machine_i2s_init0() {
    for (i2s_port_t p = 0; p < I2S_NUM_AUTO; p++) {
        MP_STATE_PORT(machine_i2s_obj)[p] = NULL;
    }
}

//  The following function takes a sample buffer and swaps L/R channels
//
//  Background:  For 32-bit stereo, the ESP-IDF API has a L/R channel orientation that breaks
//               convention with other ESP32 channel formats
//
//   appbuf[] = [L_0-7, L_8-15, L_16-23, L_24-31, R_0-7, R_8-15, R_16-23, R_24-31] = [Left channel, Right channel]
//   dma[] =    [R_0-7, R_8-15, R_16-23, R_24-31, L_0-7, L_8-15, L_16-23, L_24-31] = [Right channel, Left channel]
//
//   where:
//     L_0-7 is the least significant byte of the 32 bit sample in the Left channel
//     L_24-31 is the most significant byte of the 32 bit sample in the Left channel
//
//  Example:
//
//   appbuf[] = [0x99, 0xBB, 0x11, 0x22, 0x44, 0x55, 0xAB, 0x77] = [Left channel, Right channel]
//   dma[] =    [0x44, 0x55, 0xAB, 0x77, 0x99, 0xBB, 0x11, 0x22] = [Right channel,  Left channel]
//   where:
//      LEFT Channel =  0x99, 0xBB, 0x11, 0x22
//      RIGHT Channel = 0x44, 0x55, 0xAB, 0x77
//
//    samples in appbuf are in little endian format:
//       0x77 is the most significant byte of the 32-bit sample
//       0x44 is the least significant byte of the 32-bit sample
STATIC void swap_32_bit_stereo_channels(mp_buffer_info_t *bufinfo) {
    int32_t swap_sample;
    int32_t *sample = bufinfo->buf;
    uint32_t num_samples = bufinfo->len / 4;
    for (uint32_t i = 0; i < num_samples; i += 2) {
        swap_sample = sample[i + 1];
        sample[i + 1] = sample[i];
        sample[i] = swap_sample;
    }
}

STATIC int8_t get_frame_mapping_index(i2s_bits_per_sample_t bits, format_t format) {
    if (format == MONO) {
        if (bits == I2S_BITS_PER_SAMPLE_16BIT) {
            return 0;
        } else { // 32 bits
            return 1;
        }
    } else { // STEREO
        if (bits == I2S_BITS_PER_SAMPLE_16BIT) {
            return 2;
        } else { // 32 bits
            return 3;
        }
    }
}

STATIC i2s_bits_per_sample_t get_dma_bits(uint8_t mode, i2s_bits_per_sample_t bits) {
    if (mode == (I2S_MODE_MASTER | I2S_MODE_TX)) {
        return bits;
    } else { // Master Rx
        // read 32 bit samples for I2S hardware.  e.g. MEMS microphones
        return I2S_BITS_PER_SAMPLE_32BIT;
    }
}

STATIC i2s_channel_fmt_t get_dma_format(uint8_t mode, format_t format) {
    if (mode == (I2S_MODE_MASTER | I2S_MODE_TX)) {
        if (format == MONO) {
            return I2S_CHANNEL_FMT_ONLY_LEFT;
        } else {  // STEREO
            return I2S_CHANNEL_FMT_RIGHT_LEFT;
        }
    } else { // Master Rx
        // read stereo frames for all I2S hardware
        return I2S_CHANNEL_FMT_RIGHT_LEFT;
    }
}

STATIC uint32_t get_dma_buf_count(uint8_t mode, i2s_bits_per_sample_t bits, format_t format, int32_t ibuf) {
    // calculate how many DMA buffers need to be allocated
    uint32_t dma_frame_size_in_bytes =
        (get_dma_bits(mode, bits) / 8) * (get_dma_format(mode, format) == I2S_CHANNEL_FMT_RIGHT_LEFT ? 2: 1);

    uint32_t dma_buf_count = ibuf / (DMA_BUF_LEN_IN_I2S_FRAMES * dma_frame_size_in_bytes);

    return dma_buf_count;
}

STATIC uint32_t fill_appbuf_from_dma(machine_i2s_obj_t *self, mp_buffer_info_t *appbuf) {

    // copy audio samples from DMA memory to the app buffer
    // audio samples are read from DMA memory in chunks
    // loop, reading and copying chunks until the app buffer is filled
    // For asyncio mode, the loop will make an early exit if DMA memory becomes empty
    // Example:
    //   a MicroPython I2S object is configured for 16-bit mono (2 bytes per audio sample).
    //   For every frame coming from DMA (8 bytes), 2 bytes are "cherry picked" and
    //   copied to the supplied app buffer.
    //   Thus, for every 1 byte copied to the app buffer, 4 bytes are read from DMA memory.
    //   If a 8kB app buffer is supplied, 32kB of audio samples is read from DMA memory.

    uint32_t a_index = 0;
    uint8_t *app_p = appbuf->buf;
    uint8_t appbuf_sample_size_in_bytes = (self->bits / 8) * (self->format == STEREO ? 2: 1);
    uint32_t num_bytes_needed_from_dma = appbuf->len * (I2S_RX_FRAME_SIZE_IN_BYTES / appbuf_sample_size_in_bytes);
    while (num_bytes_needed_from_dma) {
        size_t num_bytes_requested_from_dma = MIN(sizeof(self->transform_buffer), num_bytes_needed_from_dma);
        size_t num_bytes_received_from_dma = 0;

        TickType_t delay;
        if (self->io_mode == ASYNCIO) {
            delay = 0; // stop i2s_read() operation if DMA memory becomes empty
        } else {
            delay = portMAX_DELAY;  // block until supplied buffer is filled
        }

        esp_err_t ret = i2s_read(
            self->i2s_id,
            self->transform_buffer,
            num_bytes_requested_from_dma,
            &num_bytes_received_from_dma,
            delay);
        check_esp_err(ret);

        // process the transform buffer one frame at a time.
        // copy selected bytes from the transform buffer into the user supplied appbuf.
        // Example:
        //   a MicroPython I2S object is configured for 16-bit mono.  This configuration associates to
        //   a frame map index of 0 = { 6,  7, -1, -1, -1, -1, -1, -1 } in the i2s_frame_map array
        //   This mapping indicates:
        //      appbuf[x+0] = frame[6]
        //      appbuf[x+1] = frame[7]
        //      frame bytes 0-5 are not used

        uint32_t t_index = 0;
        uint8_t f_index = get_frame_mapping_index(self->bits, self->format);
        while (t_index < num_bytes_received_from_dma) {
            uint8_t *transform_p = self->transform_buffer + t_index;

            for (uint8_t i = 0; i < I2S_RX_FRAME_SIZE_IN_BYTES; i++) {
                int8_t t_to_a_mapping = i2s_frame_map[f_index][i];
                if (t_to_a_mapping != -1) {
                    *app_p++ = transform_p[t_to_a_mapping];
                    a_index++;
                }
                t_index++;
            }
        }

        num_bytes_needed_from_dma -= num_bytes_received_from_dma;

        if ((self->io_mode == ASYNCIO) && (num_bytes_received_from_dma < num_bytes_requested_from_dma)) {
            // Unable to fill the entire app buffer from DMA memory.  This indicates all DMA RX buffers are empty.
            // Clear the I2S event queue so ioctl() indicates that the I2S object cannot currently
            // supply more audio samples
            xQueueReset(self->i2s_event_queue);
            break;
        }
    }

    return a_index;
}

STATIC size_t copy_appbuf_to_dma(machine_i2s_obj_t *self, mp_buffer_info_t *appbuf) {
    if ((self->bits == I2S_BITS_PER_SAMPLE_32BIT) && (self->format == STEREO)) {
        swap_32_bit_stereo_channels(appbuf);
    }

    size_t num_bytes_written = 0;

    TickType_t delay;
    if (self->io_mode == ASYNCIO) {
        delay = 0;  // stop i2s_write() operation if DMA memory becomes full
    } else {
        delay = portMAX_DELAY;  // block until supplied buffer is emptied
    }

    esp_err_t ret = i2s_write(self->i2s_id, appbuf->buf, appbuf->len, &num_bytes_written, delay);
    check_esp_err(ret);

    if ((self->io_mode == ASYNCIO) && (num_bytes_written < appbuf->len)) {
        // Unable to empty the entire app buffer into DMA memory.  This indicates all DMA TX buffers are full.
        // Clear the I2S event queue so ioctl() indicates that the I2S object cannot currently
        // accept more audio samples
        xQueueReset(self->i2s_event_queue);

        // Undo the swap transformation as the buffer has not been completely emptied.
        // The asyncio stream writer will use the same buffer in a future write call.
        if ((self->bits == I2S_BITS_PER_SAMPLE_32BIT) && (self->format == STEREO)) {
            swap_32_bit_stereo_channels(appbuf);
        }
    }
    return num_bytes_written;
}

// FreeRTOS task used for non-blocking mode
STATIC void task_for_non_blocking_mode(void *self_in) {
    machine_i2s_obj_t *self = (machine_i2s_obj_t *)self_in;

    non_blocking_descriptor_t descriptor;

    for (;;) {
        if (xQueueReceive(self->non_blocking_mode_queue, &descriptor, portMAX_DELAY)) {
            if (descriptor.direction == I2S_TX_TRANSFER) {
                copy_appbuf_to_dma(self, &descriptor.appbuf);
            } else { // RX
                fill_appbuf_from_dma(self, &descriptor.appbuf);
            }
            mp_sched_schedule(descriptor.callback, MP_OBJ_FROM_PTR(self));
        }
    }
}

STATIC void mp_machine_i2s_init_helper(machine_i2s_obj_t *self, mp_arg_val_t *args) {
    // are Pins valid?
    int8_t sck = args[ARG_sck].u_obj == MP_OBJ_NULL ? -1 : machine_pin_get_id(args[ARG_sck].u_obj);
    int8_t ws = args[ARG_ws].u_obj == MP_OBJ_NULL ? -1 : machine_pin_get_id(args[ARG_ws].u_obj);
    int8_t sd = args[ARG_sd].u_obj == MP_OBJ_NULL ? -1 : machine_pin_get_id(args[ARG_sd].u_obj);

    // is Mode valid?
    i2s_mode_t mode = args[ARG_mode].u_int;
    if ((mode != (I2S_MODE_MASTER | I2S_MODE_RX)) &&
        (mode != (I2S_MODE_MASTER | I2S_MODE_TX))) {
        mp_raise_ValueError(MP_ERROR_TEXT("invalid mode"));
    }

    // is Bits valid?
    i2s_bits_per_sample_t bits = args[ARG_bits].u_int;
    if ((bits != I2S_BITS_PER_SAMPLE_16BIT) &&
        (bits != I2S_BITS_PER_SAMPLE_32BIT)) {
        mp_raise_ValueError(MP_ERROR_TEXT("invalid bits"));
    }

    // is Format valid?
    format_t format = args[ARG_format].u_int;
    if ((format != STEREO) &&
        (format != MONO)) {
        mp_raise_ValueError(MP_ERROR_TEXT("invalid format"));
    }

    // is Rate valid?
    // Not checked:  ESP-IDF I2S API does not indicate a valid range for sample rate

    // is Ibuf valid?
    // Not checked: ESP-IDF I2S API will return error if requested buffer size exceeds available memory

    self->sck = sck;
    self->ws = ws;
    self->sd = sd;
    self->mode = mode;
    self->bits = bits;
    self->format = format;
    self->rate = args[ARG_rate].u_int;
    self->ibuf = args[ARG_ibuf].u_int;
    self->callback_for_non_blocking = MP_OBJ_NULL;
    self->i2s_event_queue = NULL;
    self->non_blocking_mode_queue = NULL;
    self->non_blocking_mode_task = NULL;
    self->io_mode = BLOCKING;

    i2s_config_t i2s_config;
    i2s_config.communication_format = I2S_COMM_FORMAT_STAND_I2S;
    i2s_config.mode = mode;
    i2s_config.bits_per_sample = get_dma_bits(mode, bits);
    i2s_config.channel_format = get_dma_format(mode, format);
    i2s_config.sample_rate = self->rate;
    i2s_config.intr_alloc_flags = ESP_INTR_FLAG_LOWMED;
    i2s_config.dma_desc_num = get_dma_buf_count(mode, bits, format, self->ibuf);
    i2s_config.dma_frame_num = DMA_BUF_LEN_IN_I2S_FRAMES;
    i2s_config.use_apll = false;
    i2s_config.tx_desc_auto_clear = true;
    i2s_config.fixed_mclk = 0;
    i2s_config.mclk_multiple = I2S_MCLK_MULTIPLE_256;
    i2s_config.bits_per_chan = 0;

    // I2S queue size equals the number of DMA buffers
    check_esp_err(i2s_driver_install(self->i2s_id, &i2s_config, i2s_config.dma_desc_num, &self->i2s_event_queue));

    // apply low-level workaround for bug in some ESP-IDF versions that swap
    // the left and right channels
    // https://github.com/espressif/esp-idf/issues/6625
    #if CONFIG_IDF_TARGET_ESP32S3
    REG_SET_BIT(I2S_TX_CONF_REG(self->i2s_id), I2S_TX_MSB_SHIFT);
    REG_SET_BIT(I2S_TX_CONF_REG(self->i2s_id), I2S_RX_MSB_SHIFT);
    #else
    REG_SET_BIT(I2S_CONF_REG(self->i2s_id), I2S_TX_MSB_RIGHT);
    REG_SET_BIT(I2S_CONF_REG(self->i2s_id), I2S_RX_MSB_RIGHT);
    #endif

    i2s_pin_config_t pin_config;
    pin_config.mck_io_num = I2S_PIN_NO_CHANGE;
    pin_config.bck_io_num = self->sck;
    pin_config.ws_io_num = self->ws;

    if (mode == (I2S_MODE_MASTER | I2S_MODE_RX)) {
        pin_config.data_in_num = self->sd;
        pin_config.data_out_num = I2S_PIN_NO_CHANGE;
    } else { // TX
        pin_config.data_in_num = I2S_PIN_NO_CHANGE;
        pin_config.data_out_num = self->sd;
    }

    check_esp_err(i2s_set_pin(self->i2s_id, &pin_config));
}

STATIC machine_i2s_obj_t *mp_machine_i2s_make_new_instance(mp_int_t i2s_id) {
    if (i2s_id < 0 || i2s_id >= I2S_NUM_AUTO) {
        mp_raise_ValueError(MP_ERROR_TEXT("invalid id"));
    }

    machine_i2s_obj_t *self;
    if (MP_STATE_PORT(machine_i2s_obj)[i2s_id] == NULL) {
        self = mp_obj_malloc_with_finaliser(machine_i2s_obj_t, &machine_i2s_type);
        MP_STATE_PORT(machine_i2s_obj)[i2s_id] = self;
        self->i2s_id = i2s_id;
    } else {
        self = MP_STATE_PORT(machine_i2s_obj)[i2s_id];
        machine_i2s_deinit(self);
    }

    return self;
}

STATIC void mp_machine_i2s_deinit(machine_i2s_obj_t *self) {
    i2s_driver_uninstall(self->i2s_id);

    if (self->non_blocking_mode_task != NULL) {
        vTaskDelete(self->non_blocking_mode_task);
        self->non_blocking_mode_task = NULL;
    }

    if (self->non_blocking_mode_queue != NULL) {
        vQueueDelete(self->non_blocking_mode_queue);
        self->non_blocking_mode_queue = NULL;
    }

    self->i2s_event_queue = NULL;
}

STATIC void mp_machine_i2s_irq_update(machine_i2s_obj_t *self) {
    if (self->io_mode == NON_BLOCKING) {
        // create a queue linking the MicroPython task to a FreeRTOS task
        // that manages the non blocking mode of operation
        self->non_blocking_mode_queue = xQueueCreate(1, sizeof(non_blocking_descriptor_t));

        // non-blocking mode requires a background FreeRTOS task
        if (xTaskCreatePinnedToCore(
            task_for_non_blocking_mode,
            "i2s_non_blocking",
            I2S_TASK_STACK_SIZE,
            self,
            I2S_TASK_PRIORITY,
            (TaskHandle_t *)&self->non_blocking_mode_task,
            MP_TASK_COREID) != pdPASS) {

            mp_raise_msg(&mp_type_RuntimeError, MP_ERROR_TEXT("failed to create I2S task"));
        }
    } else {
        if (self->non_blocking_mode_task != NULL) {
            vTaskDelete(self->non_blocking_mode_task);
            self->non_blocking_mode_task = NULL;
        }

        if (self->non_blocking_mode_queue != NULL) {
            vQueueDelete(self->non_blocking_mode_queue);
            self->non_blocking_mode_queue = NULL;
        }
    }
}

MP_REGISTER_ROOT_POINTER(struct _machine_i2s_obj_t *machine_i2s_obj[I2S_NUM_AUTO]);