Parallel IO

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

Warning

At the moment, the Parallel IO driver only supports TX mode. The RX feature is still working in progress.

Application Examples

API Reference

Header File

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 transcation 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

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

struct parlio_tx_unit_config_t::[anonymous] 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::[anonymous] 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

Type Definitions

typedef struct parlio_tx_unit_t *parlio_tx_unit_handle_t

Type of Parallel IO TX unit handle.

Header File

Macros

PARLIO_TX_UNIT_MAX_DATA_WIDTH

Maximum data width of TX 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 will not forbid you from applying for more driver objects, but it will return 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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