# Parallel IO

[中文]

## Introduction

The Parallel IO peripheral is a general purpose parallel interface that can be used to connect to external devices such as LED matrix, LCD display, Printer and Camera. The peripheral has independent TX and RX units. Each unit can have up to 8 or 16 data signals plus 1 or 2 clock signals. [1]

The TX and RX driver of Parallel IO peripheral are designed separately, you can include `driver/parlio_tx.h` or `driver/parlio_rx.h` to use any of them.

## Application Examples

- peripherals/parlio/parlio_rx/logic_analyzer demonstrates how to implement a logic analyzer using the Parallel IO RX peripheral, which can sample data on multiple GPIOs in parallel at a high rate, and provides options to probe either internal or external signals and output the raw data via flash or TCP stream.

- peripherals/parlio/parlio_tx/simple_rgb_led_matrix demonstrates how to use the Parallel IO TX unit of ESP32-H2 to drive a RGB LED Matrix board with a HUB75 interface, using the LVGL library to display simple UI elements.

## API Reference

### Header File

- components/esp_driver_parlio/include/driver/parlio_tx.h

- This header file can be included with:

  >     #include "driver/parlio_tx.h"

- This header file is a part of the API provided by the `esp_driver_parlio` component. To declare that your component depends on `esp_driver_parlio`, add the following to your CMakeLists.txt:

  >     REQUIRES esp_driver_parlio

  > or

  >     PRIV_REQUIRES esp_driver_parlio

### Functions

esp_err_t parlio_new_tx_unit(const parlio_tx_unit_config_t *config, parlio_tx_unit_handle_t *ret_unit)

  Create a Parallel IO TX unit.

  Parameters:

    - config -- [in] Parallel IO TX unit configuration

    - ret_unit -- [out] Returned Parallel IO TX unit handle

  Returns:

    - ESP_OK: Create Parallel IO TX unit successfully

    - ESP_ERR_INVALID_ARG: Create Parallel IO TX unit failed because of invalid argument

    - ESP_ERR_NO_MEM: Create Parallel IO TX unit failed because of out of memory

    - ESP_ERR_NOT_FOUND: Create Parallel IO TX unit failed because all TX units are used up and no more free one

    - ESP_ERR_NOT_SUPPORTED: Create Parallel IO TX unit failed because some feature is not supported by hardware, e.g. clock gating

    - ESP_FAIL: Create Parallel IO TX unit failed because of other error

esp_err_t parlio_del_tx_unit(parlio_tx_unit_handle_t unit)

  Delete a Parallel IO TX unit.

  Parameters:

    unit -- [in] Parallel IO TX unit that created by `parlio_new_tx_unit`

  Returns:

    - ESP_OK: Delete Parallel IO TX unit successfully

    - ESP_ERR_INVALID_ARG: Delete Parallel IO TX unit failed because of invalid argument

    - ESP_ERR_INVALID_STATE: Delete Parallel IO TX unit failed because it is still in working

    - ESP_FAIL: Delete Parallel IO TX unit failed because of other error

esp_err_t parlio_tx_unit_enable(parlio_tx_unit_handle_t unit)

  Enable the Parallel IO TX unit.

  Note

  This function will transit the driver state from init to enable

  Note

  This function will acquire a PM lock that might be installed during channel allocation

  Note

  If there're transaction pending in the queue, this function will pick up the first one and start the transfer

  Parameters:

    unit -- [in] Parallel IO TX unit that created by `parlio_new_tx_unit`

  Returns:

    - ESP_OK: Enable Parallel IO TX unit successfully

    - ESP_ERR_INVALID_ARG: Enable Parallel IO TX unit failed because of invalid argument

    - ESP_ERR_INVALID_STATE: Enable Parallel IO TX unit failed because it is already enabled

    - ESP_FAIL: Enable Parallel IO TX unit failed because of other error

esp_err_t parlio_tx_unit_disable(parlio_tx_unit_handle_t unit)

  Disable the Parallel IO TX unit.

  Note

  This function will transit the driver state from enable to init

  Note

  This function will release the PM lock that might be installed during channel allocation

  Note

  If one transaction is undergoing, this function will terminate it immediately

  Parameters:

    unit -- [in] Parallel IO TX unit that created by `parlio_new_tx_unit`

  Returns:

    - ESP_OK: Disable Parallel IO TX unit successfully

    - ESP_ERR_INVALID_ARG: Disable Parallel IO TX unit failed because of invalid argument

    - ESP_ERR_INVALID_STATE: Disable Parallel IO TX unit failed because it's not enabled yet

    - ESP_FAIL: Disable Parallel IO TX unit failed because of other error

esp_err_t parlio_tx_unit_register_event_callbacks(parlio_tx_unit_handle_t tx_unit, const parlio_tx_event_callbacks_t *cbs, void *user_data)

  Set event callbacks for Parallel IO TX unit.

  Note

  User can deregister a previously registered callback by calling this function and setting the callback member in the `cbs` structure to NULL.

  Note

  When CONFIG_PARLIO_ISR_IRAM_SAFE is enabled, the callback itself and functions called by it should be placed in IRAM. The variables used in the function should be in the SRAM as well. The `user_data` should also reside in SRAM.

  Parameters:

    - tx_unit -- [in] Parallel IO TX unit that created by `parlio_new_tx_unit`

    - cbs -- [in] Group of callback functions

    - user_data -- [in] User data, which will be passed to callback functions directly

  Returns:

    - ESP_OK: Set event callbacks successfully

    - ESP_ERR_INVALID_ARG: Set event callbacks failed because of invalid argument

    - ESP_FAIL: Set event callbacks failed because of other error

esp_err_t parlio_tx_unit_transmit(parlio_tx_unit_handle_t tx_unit, const void *payload, size_t payload_bits, const parlio_transmit_config_t *config)

  Transmit data on by Parallel IO TX unit.

  Note

  After the function returns, it doesn't mean the transaction is finished. This function only constructs a transaction structure and push into a queue.

  Parameters:

    - tx_unit -- [in] Parallel IO TX unit that created by `parlio_new_tx_unit`

    - payload -- [in] Pointer to the data to be transmitted

    - payload_bits -- [in] Length of the data to be transmitted, in bits

    - config -- [in] Transmit configuration

  Returns:

    - ESP_OK: Transmit data successfully

    - ESP_ERR_INVALID_ARG: Transmit data failed because of invalid argument

    - ESP_ERR_INVALID_STATE: Transmit data failed because the Parallel IO TX unit is not enabled

    - ESP_FAIL: Transmit data failed because of other error

esp_err_t parlio_tx_unit_wait_all_done(parlio_tx_unit_handle_t tx_unit, int timeout_ms)

  Wait for all pending TX transactions done.

  Parameters:

    - tx_unit -- [in] Parallel IO TX unit that created by `parlio_new_tx_unit`

    - timeout_ms -- [in] Timeout in milliseconds, `-1` means to wait forever

  Returns:

    - ESP_OK: All pending TX transactions is finished and recycled

    - ESP_ERR_INVALID_ARG: Wait for all pending TX transactions done failed because of invalid argument

    - ESP_ERR_TIMEOUT: Wait for all pending TX transactions done timeout

    - ESP_FAIL: Wait for all pending TX transactions done failed because of other error

### Structures

struct parlio_tx_unit_config_t

  Parallel IO TX unit configuration.

  Public Members

  parlio_clock_source_t clk_src

    Parallel IO internal clock source

  gpio_num_t clk_in_gpio_num

    If the clock source is input from external, set the corresponding GPIO number. Otherwise, set to `-1` and the driver will use the internal `clk_src` as clock source. This option has higher priority than `clk_src`

  uint32_t input_clk_src_freq_hz

    Frequency of the input clock source, valid only if `clk_in_gpio_num` is not `-1`

  uint32_t output_clk_freq_hz

    Frequency of the output clock. It's divided from either internal `clk_src` or external clock source

  size_t data_width

    Parallel IO data width, can set to 1/2/4/8/..., but can't bigger than PARLIO_TX_UNIT_MAX_DATA_WIDTH

  gpio_num_t data_gpio_nums[PARLIO_TX_UNIT_MAX_DATA_WIDTH]

    Parallel IO data GPIO numbers, if any GPIO is not used, you can set it to `-1`

  gpio_num_t clk_out_gpio_num

    GPIO number of the output clock signal, the clock is synced with TX data

  gpio_num_t valid_gpio_num

    GPIO number of the valid signal, which stays high when transferring data. Note that, the valid signal will always occupy the MSB data bit

  size_t trans_queue_depth

    Depth of internal transaction queue

  size_t max_transfer_size

    Maximum transfer size in one transaction, in bytes. This decides the number of DMA nodes will be used for each transaction

  size_t dma_burst_size

    DMA burst size, in bytes

  parlio_sample_edge_t sample_edge

    Parallel IO sample edge

  parlio_bit_pack_order_t bit_pack_order

    Set the order of packing the bits into bytes (only works when `data_width` < 8)

  uint32_t clk_gate_en

    Enable TX clock gating, the output clock will be controlled by the MSB bit of the data bus, i.e. by data_gpio_nums[PARLIO_TX_UNIT_MAX_DATA_WIDTH-1]. High level to enable the clock output, low to disable

  uint32_t io_loop_back

    For debug/test, the signal output from the GPIO will be fed to the input path as well

  uint32_t allow_pd

    Set to allow power down. When this flag set, the driver will backup/restore the PARLIO registers before/after entering/exist sleep mode. By this approach, the system can power off PARLIO's power domain. This can save power, but at the expense of more RAM being consumed.

  struct parlio_tx_unit_config_t flags

    Extra configuration flags

struct parlio_tx_done_event_data_t

  Type of Parallel IO TX done event data.

struct parlio_tx_event_callbacks_t

  Group of Parallel IO TX callbacks.

  Note

  The callbacks are all running under ISR environment

  Note

  When CONFIG_PARLIO_ISR_IRAM_SAFE is enabled, the callback itself and functions called by it should be placed in IRAM. The variables used in the function should be in the SRAM as well.

  Public Members

  parlio_tx_done_callback_t on_trans_done

    Event callback, invoked when one transmission is finished

struct parlio_transmit_config_t

  Parallel IO transmit configuration.

  Public Members

  uint32_t idle_value

    The value on the data line when the parallel IO is in idle state

  uint32_t queue_nonblocking

    If set, when the transaction queue is full, driver will not block the thread but return directly

  struct parlio_transmit_config_t flags

    Transmit specific config flags

### Type Definitions

typedef bool (*parlio_tx_done_callback_t)(parlio_tx_unit_handle_t tx_unit, const parlio_tx_done_event_data_t *edata, void *user_ctx)

  Prototype of parlio tx event callback.

  Param tx_unit:

    [in] Parallel IO TX unit that created by `parlio_new_tx_unit`

  Param edata:

    [in] Point to Parallel IO TX event data. The lifecycle of this pointer memory is inside this function, user should copy it into static memory if used outside this function.

  Param user_ctx:

    [in] User registered context, passed from `parlio_tx_unit_register_event_callbacks`

  Return:

    Whether a high priority task has been waken up by this callback function

### Header File

- components/esp_driver_parlio/include/driver/parlio_rx.h

- This header file can be included with:

  >     #include "driver/parlio_rx.h"

- This header file is a part of the API provided by the `esp_driver_parlio` component. To declare that your component depends on `esp_driver_parlio`, add the following to your CMakeLists.txt:

  >     REQUIRES esp_driver_parlio

  > or

  >     PRIV_REQUIRES esp_driver_parlio

### Functions

esp_err_t parlio_new_rx_unit(const parlio_rx_unit_config_t *config, parlio_rx_unit_handle_t *ret_unit)

  Create a Parallel IO RX unit.

  Parameters:

    - config -- [in] Parallel IO RX unit configuration

    - ret_unit -- [out] Returned Parallel IO RX unit handle

  Returns:

    - ESP_ERR_INVALID_ARG Invalid arguments in the parameter list or the rx unit configuration

    - ESP_ERR_NOT_FOUND No available rx unit found

    - ESP_ERR_NO_MEM No enough memory for the rx unit resources

    - ESP_OK Success to allocate the rx unit

esp_err_t parlio_del_rx_unit(parlio_rx_unit_handle_t rx_unit)

  Delete a Parallel IO RX unit.

  Parameters:

    rx_unit -- [in] Parallel IO RX unit handle that created by `parlio_new_rx_unit`

  Returns:

    - ESP_ERR_INVALID_ARG rx_unit is NULL

    - ESP_ERR_INVALID_STATE The rx unit is enabled, can't delete an enabled rx unit

    - ESP_OK Success to delete the rx unit

esp_err_t parlio_new_rx_level_delimiter(const parlio_rx_level_delimiter_config_t *config, parlio_rx_delimiter_handle_t *ret_delimiter)

  Create a level delimiter.

  Note

  This function only allocate the software resources, the hardware configurations will lazy installed while the transaction that using this delimiter start processing

  Note

  The enable signal must be aligned with the valid data.

  Note

  There're at most `SOC_PARLIO_RX_UNIT_MAX_DATA_WIDTH - 1` IO pins left for RXD

  Parameters:

    - config -- [in] Level delimiter configuration

    - ret_delimiter -- [out] Returned delimiter handle

  Returns:

    - ESP_ERR_INVALID_ARG Invalid arguments in the parameter list or the level delimiter configuration

    - ESP_ERR_NO_MEM No enough memory for the level delimiter resources

    - ESP_OK Success to allocate the level delimiter

esp_err_t parlio_new_rx_pulse_delimiter(const parlio_rx_pulse_delimiter_config_t *config, parlio_rx_delimiter_handle_t *ret_delimiter)

  Create a pulse delimiter.

  Note

  This function only allocate the software resources, the hardware configurations will lazy installed while the transaction that using this delimiter start processing

  Note

  There're at most `SOC_PARLIO_RX_UNIT_MAX_DATA_WIDTH - 1` IO pins left for RXD

  Parameters:

    - config -- [in] Pulse delimiter configuration

    - ret_delimiter -- [out] Returned delimiter handle

  Returns:

    - ESP_ERR_INVALID_ARG Invalid arguments in the parameter list or the pulse delimiter configuration

    - ESP_ERR_NO_MEM No enough memory for the pulse delimiter resources

    - ESP_OK Success to allocate the pulse delimiter

esp_err_t parlio_new_rx_soft_delimiter(const parlio_rx_soft_delimiter_config_t *config, parlio_rx_delimiter_handle_t *ret_delimiter)

  Create a pulse delimiter.

  Note

  This function only allocate the software resources, the hardware configurations will lazy installed while the transaction that using this delimiter start processing

  Parameters:

    - config -- [in] Soft delimiter configuration

    - ret_delimiter -- [out] Returned delimiter handle

  Returns:

    - ESP_ERR_INVALID_ARG Invalid arguments in the parameter list or the soft delimiter configuration

    - ESP_ERR_NO_MEM No enough memory for the soft delimiter resources

    - ESP_OK Success to allocate the soft delimiter

esp_err_t parlio_rx_soft_delimiter_start_stop(parlio_rx_unit_handle_t rx_unit, parlio_rx_delimiter_handle_t delimiter, bool start_stop)

  Start/stop the soft delimiter.

  Note

  Soft delimiter need to start or stop manually because it has no validating/enabling signal to indicate the data has started or stopped

  Parameters:

    - rx_unit -- [in] Parallel IO RX unit handle that created by `parlio_new_rx_unit`

    - delimiter -- [in] Delimiter handle

    - start_stop -- [in] Set true to start, set false to stop

  Returns:

    - ESP_ERR_INVALID_ARG Invalid arguments in the parameter list or not soft delimiter

    - ESP_ERR_INVALID_STATE The rx unit not enabled

    - ESP_OK Success to start or stop the soft delimiter

esp_err_t parlio_del_rx_delimiter(parlio_rx_delimiter_handle_t delimiter)

  Delete the delimiter.

  Note

  To delete the delimiter safely, please delete it after disable all the RX units

  Parameters:

    delimiter -- [in] Delimiter handle

  Returns:

    - ESP_ERR_INVALID_ARG The input delimiter is NULL

    - ESP_ERR_INVALID_STATE The delimiter is on receiving

    - ESP_OK Success to delete the delimiter

esp_err_t parlio_rx_unit_enable(parlio_rx_unit_handle_t rx_unit, bool reset_queue)

  Enable the Parallel IO RX unit.

  Parameters:

    - rx_unit -- [in] Parallel IO RX unit handle that created by `parlio_new_rx_unit`

    - reset_queue -- [in] Whether to reset the receiving queue. If set to false, the legacy receive transactions in the queue are still available, If set to true, the legacy receive transactions in the queue are dropped.

  Returns:

    - ESP_ERR_INVALID_ARG The input rx_unit is NULL

    - ESP_ERR_INVALID_STATE The rx unit has been enabled

    - ESP_OK Success to enable the rx unit

esp_err_t parlio_rx_unit_disable(parlio_rx_unit_handle_t rx_unit)

  Disable the Parallel IO RX unit.

  Parameters:

    rx_unit -- [in] Parallel IO RX unit handle that created by `parlio_new_rx_unit`

  Returns:

    - ESP_ERR_INVALID_ARG The input rx_unit is NULL

    - ESP_ERR_INVALID_STATE The rx unit has been disabled

    - ESP_OK Success to disable the rx unit

esp_err_t parlio_rx_unit_receive(parlio_rx_unit_handle_t rx_unit, void *payload, size_t payload_size, const parlio_receive_config_t *recv_cfg)

  Receive data by Parallel IO RX unit.

  Note

  This is a non-blocking and asynchronous function. To block or realize synchronous receive, please call `parlio_rx_unit_wait_all_done` after this function

  Note

  The receive transaction will start immediately when there is not other transaction on receiving, Otherwise it will be sent to the transaction queue to wait for the bus.

  Parameters:

    - rx_unit -- [in] Parallel IO RX unit handle that created by `parlio_new_rx_unit`

    - payload -- [in] The payload buffer pointer

    - payload_size -- [in] The size of the payload buffer, in bytes.

    - recv_cfg -- [in] The configuration of this receive transaction

  Returns:

    - ESP_ERR_INVALID_ARG Invalid arguments in the parameter list or the receive configuration

    - ESP_ERR_NO_MEM No memory for the internal DMA buffer (only when parlio_receive_config_t::indirect_mount enabled)

    - ESP_ERR_INVALID_STATE Transaction queue is full, failed to queue the current transaction. Or the internal buffer is under using by an infinite transaction, can't allocate a new one

    - ESP_OK Success to queue the current receiving transaction

esp_err_t parlio_rx_unit_wait_all_done(parlio_rx_unit_handle_t rx_unit, int timeout_ms)

  Wait for all pending RX transactions done.

  Note

  This function will block until all receiving transactions done or timeout. When timeout occurs, either the timeout limitation too short for all transactions done, or the peripheral got stuck and no more interrupts trigger (e.g., external clock stopped).

  Parameters:

    - rx_unit -- [in] Parallel IO RX unit handle that created by `parlio_new_rx_unit`

    - timeout_ms -- [in] Timeout in milliseconds, `-1` means to wait forever (software timeout)

  Returns:

    - ESP_ERR_INVALID_ARG The input rx_unit is NULL

    - ESP_ERR_TIMEOUT Wait for all transactions done timeout

    - ESP_OK All transaction done

esp_err_t parlio_rx_unit_register_event_callbacks(parlio_rx_unit_handle_t rx_unit, const parlio_rx_event_callbacks_t *cbs, void *user_data)

  Register event callbacks for Parallel IO RX unit.

  Parameters:

    - rx_unit -- [in] Parallel IO RX unit handle that created by `parlio_new_rx_unit`

    - cbs -- [in] Callback group, set callback to NULL to deregister the corresponding callback (callback group pointer shouldn't be NULL)

    - user_data -- [in] User specified data that will be transported to the callbacks

  Returns:

    - ESP_ERR_INVALID_ARG The input rx_unit is NULL

    - ESP_ERR_INVALID_STATE The rx unit has been enabled, callback should be registered before enabling the unit

    - ESP_OK Success to register the callbacks

### Structures

struct parlio_rx_unit_config_t

  Parallel IO RX unit configuration.

  Public Members

  size_t trans_queue_depth

    Depth of internal transaction queue

  size_t max_recv_size

    Maximum receive size in one transaction, in bytes. This decides the number of DMA nodes will be used for each transaction

  size_t data_width

    Parallel IO data width, can set to 1/2/4/8/..., but can't be greater than PARLIO_RX_UNIT_MAX_DATA_WIDTH

  parlio_clock_source_t clk_src

    Parallel IO clock source

  uint32_t ext_clk_freq_hz

    The external source clock frequency. Only be valid when select PARLIO_CLK_SRC_EXTERNAL as clock source

  uint32_t exp_clk_freq_hz

    The expected sample/bit clock frequency, which is divided from the internal or external clock regarding the clock source

  gpio_num_t clk_in_gpio_num

    The the external clock input pin. Only be valid when select PARLIO_CLK_SRC_EXTERNAL as clock source. Set to -1 if not needed

  gpio_num_t clk_out_gpio_num

    The sample/bit clock output pin. Set to -1 if not needed

  gpio_num_t valid_gpio_num

    GPIO number of the valid signal. The signal on this pin is used to indicate whether the data on the data lines are valid. Only takes effect when using level or pulse delimiter, set to `-1` if only use the soft delimiter

  gpio_num_t data_gpio_nums[PARLIO_RX_UNIT_MAX_DATA_WIDTH]

    Parallel IO data GPIO numbers, set to `-1` if it's not used, The driver will take [0 .. (data_width - 1)] as the data pins

  uint32_t free_clk

    Whether the input external clock is a free-running clock. A free-running clock will always keep running (e.g. I2S bclk), a non-free-running clock will start when there are data transporting and stop when the bus idle (e.g. SPI). This flag only takes effect when select PARLIO_CLK_SRC_EXTERNAL as clock source

  uint32_t clk_gate_en

    Enable RX clock gating, only available when the clock direction is output(not supported on ESP32-C6) the output clock will be controlled by the valid gpio, i.e. high level of valid gpio to enable the clock output, low to disable

  uint32_t io_loop_back

    For debug/test, the signal output from the GPIO will be fed to the input path as well

  uint32_t io_no_init

    Deprecated. Driver won't change the GPIO configuration in inilization.

  uint32_t allow_pd

    Set to allow power down. When this flag set, the driver will backup/restore the PARLIO registers before/after entering/exist sleep mode. By this approach, the system can power off PARLIO's power domain. This can save power, but at the expense of more RAM being consumed.

  struct parlio_rx_unit_config_t flags

    RX driver flags

struct parlio_rx_level_delimiter_config_t

  Configuration of level delimiter.

  Public Members

  uint32_t valid_sig_line_id

    The data line id of valid/enable signal. The selected data line will be used as the valid/enable signal (i.e. level signal) in this delimiter. As the line of valid/enable signal is shared with the data line, this line_id will be conflict with the data line if set the id within 'data_width', therefore the range is (data_width, PARLIO_RX_UNIT_MAX_DATA_WIDTH].

  parlio_sample_edge_t sample_edge

    Parallel IO sample edge

  parlio_bit_pack_order_t bit_pack_order

    Set how we pack the bits into one bytes

  uint32_t eof_data_len

    Set the data length to trigger the End Of Frame (EOF, i.e. transaction done) interrupt, if the data length is set to `0`, that mean the EOF will only triggers when the enable signal inactivated

  uint32_t timeout_ticks

    The number of source clock ticks to trigger timeout interrupt. Set 0 to disable the receive timeout interrupt The timeout counter starts when the valid/enable signal is invalid/disabled.

  uint32_t active_low_en

    Set true to set the valid signal active when the level is low, otherwise, the valid signal becomes active when its level is high

  struct parlio_rx_level_delimiter_config_t flags

    Extra flags

struct parlio_rx_pulse_delimiter_config_t

  Configuration of pulse delimiter.

  Public Members

  uint32_t valid_sig_line_id

    The data line id of valid/enable signal. The selected data line will be used as the valid/enable signal (i.e. pulse signal) in this delimiter. As the line of valid/enable signal is shared with the data line, this line_id will be conflict with the data line if set the id within 'data_width', therefore the range is (data_width, PARLIO_RX_UNIT_MAX_DATA_WIDTH].

  parlio_sample_edge_t sample_edge

    Parallel IO sample edge

  parlio_bit_pack_order_t bit_pack_order

    Set how we pack the bits into one bytes

  uint32_t eof_data_len

    Set the data length to trigger the End Of Frame (EOF, i.e. transaction done) interrupt, if the data length is set to `0`, that mean the EOF will only triggers when the end pulse detected, please ensure there is an end pulse for a frame and `has_end_pulse` flag is set

  uint32_t timeout_ticks

    The number of source clock ticks to trigger timeout interrupt. Set 0 to disable the receive timeout interrupt The timeout counter starts when the valid/enable signal is invalid/disabled.

  uint32_t start_bit_included

    Whether data bit is included in the start pulse

  uint32_t end_bit_included

    Whether data bit is included in the end pulse, only valid when `has_end_pulse` is true

  uint32_t has_end_pulse

    Whether there's an end pulse to terminate the transaction, if no, the transaction will be terminated by user configured transaction length

  uint32_t pulse_invert

    Whether to invert the pulse

  struct parlio_rx_pulse_delimiter_config_t flags

    Extra flags

struct parlio_rx_soft_delimiter_config_t

  Configuration of soft delimiter.

  Public Members

  parlio_sample_edge_t sample_edge

    Parallel IO sample edge

  parlio_bit_pack_order_t bit_pack_order

    Set how we pack the bits into one bytes, set 1 to pack the bits into a byte from LSB, otherwise from MSB

  uint32_t eof_data_len

    Set the data length to trigger the End Of Frame (EOF, i.e. transaction done) interrupt, if the data length is set to `0`, that mean the EOF will only triggers when the end pulse detected, please ensure there is an end pulse for a frame and `parlio_rx_pulse_delimiter_config_t::has_end_pulse` flag is set

  uint32_t timeout_ticks

    The number of APB clock ticks to trigger timeout interrupt. Set 0 to disable the receive timeout interrupt

struct parlio_receive_config_t

  Configuration of a receive transaction.

  Public Members

  parlio_rx_delimiter_handle_t delimiter

    The delimiter of this receiving transaction

  uint32_t partial_rx_en

    Whether this is an infinite transaction that supposed to receive continuously and partially

  uint32_t indirect_mount

    This flag only take effect when `partial_rx_en` is enabled. Enable this flag, an INTERNAL DMA buffer will be mounted to the DMA descriptor instead, The data will be copy to the payload in every interrupt. So that to guarantee the payload buffer is valid during the `on_receive_done` callback. Either `partial_rx_en` or `indirect_mount` is disabled, the user given finite payload will be mounted to the DMA descriptor directly. By default, the user given receive payload will be mounted to the DMA descriptor directly.

  struct parlio_receive_config_t flags

    Extra flags

struct parlio_rx_event_data_t

  Event callback data.

  Public Members

  parlio_rx_delimiter_handle_t delimiter

    The current delimiter of this receiving event

  void *data

    The data buffer address that just finished receiving

  size_t recv_bytes

    The number of received bytes in the data buffer

struct parlio_rx_event_callbacks_t

  Parallel IO RX event callbacks.

  Public Members

  parlio_rx_callback_t on_partial_receive

    Callback of received partial data

  parlio_rx_callback_t on_receive_done

    Callback of receiving transaction done

  parlio_rx_callback_t on_timeout

    Callback of hardware receiving timeout

### Type Definitions

typedef bool (*parlio_rx_callback_t)(parlio_rx_unit_handle_t rx_unit, const parlio_rx_event_data_t *edata, void *user_data)

  The template of the Parallel IO RX callback function.

  Param rx_unit:

    [in] Parallel IO RX unit handle that given from ISR

  Param edata:

    [in] The event data that given from ISR

  Param user_data:

    [in] The user specified data that given while registering the callbacks

  Return:

    - True: to awoke high priority tasks

    - False: not to awoke high priority tasks

### Header File

- components/esp_driver_parlio/include/driver/parlio_types.h

- This header file can be included with:

  >     #include "driver/parlio_types.h"

- This header file is a part of the API provided by the `esp_driver_parlio` component. To declare that your component depends on `esp_driver_parlio`, add the following to your CMakeLists.txt:

  >     REQUIRES esp_driver_parlio

  > or

  >     PRIV_REQUIRES esp_driver_parlio

### Type Definitions

typedef struct parlio_tx_unit_t *parlio_tx_unit_handle_t

  Type of Parallel IO TX unit handle.

typedef struct parlio_rx_unit_t *parlio_rx_unit_handle_t

  Type of Parallel IO RX unit handle.

typedef struct parlio_rx_delimiter_t *parlio_rx_delimiter_handle_t

  Type of Parallel IO RX frame delimiter handle.

### Header File

- components/hal/include/hal/parlio_types.h

- This header file can be included with:

  >     #include "hal/parlio_types.h"

### Macros

PARLIO_TX_UNIT_MAX_DATA_WIDTH

  Maximum data width of TX unit.

PARLIO_RX_UNIT_MAX_DATA_WIDTH

  Maximum data width of RX unit.

### Type Definitions

typedef soc_periph_parlio_clk_src_t parlio_clock_source_t

  Parallel IO clock source.

  Note

  User should select the clock source based on the power and resolution requirement

### Enumerations

enum parlio_sample_edge_t

  Parallel IO sample edge.

  Values:

  enumerator PARLIO_SAMPLE_EDGE_NEG

    Sample data on falling edge of clock

  enumerator PARLIO_SAMPLE_EDGE_POS

    Sample data on rising edge of clock

enum parlio_bit_pack_order_t

  Parallel IO bit packing order.

  Data in memory: Byte 0: MSB < B0.7 B0.6 B0.5 B0.4 B0.3 B0.2 B0.1 B0.0 > LSB Byte 1: MSB < B1.7 B1.6 B1.5 B1.4 B1.3 B1.2 B1.1 B1.0 > LSB

  Output on line (PARLIO_BIT_PACK_ORDER_LSB): Cycle 0 Cycle 1 Cycle 2 &#8212;> time GPIO 0: B0.0 B0.4 B1.0 GPIO 1: B0.1 B0.5 B1.1 GPIO 2: B0.2 B0.6 B1.2 GPIO 3: B0.3 B0.7 B1.3

  Output on line (PARLIO_BIT_PACK_ORDER_MSB): Cycle 0 Cycle 1 Cycle 2 &#8212;> time GPIO 0: B0.4 B0.0 B1.4 GPIO 1: B0.5 B0.1 B1.5 GPIO 2: B0.6 B0.2 B1.6 GPIO 3: B0.7 B0.3 B1.7

  Values:

  enumerator PARLIO_BIT_PACK_ORDER_LSB

    Bit pack order: LSB

  enumerator PARLIO_BIT_PACK_ORDER_MSB

    Bit pack order: MSB

[1]

Different ESP chip series might have different numbers of PARLIO TX/RX instances, and the maximum data bus can also be different. For more details, please refer to ESP32-H2 Technical Reference Manual > Chapter Parallel IO (PARLIO) [PDF]. The driver does not forbid you from applying for more driver objects, but it returns error when all available hardware resources are used up. Please always check the return value when doing resource allocation (e.g., `parlio_new_tx_unit()`).

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