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UART Hal interface documentation

Hardware introduction

K230 integrates five UART (Universal Asynchronous Receiver and Transmitter) hardware modules. The rtsmart system occupies one serial port (serial port 0 is occupied by default), and other serial ports can be used by users.

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Data structure description

struct uart_configure

UART configuration structure, including the following members:

• baud_rate: baud rate

• data_bits: number of data digits (5-9)

• stop_bits: Stop bits (0-3 corresponds to 1-4 stop bits)

• parity: Check digit (0: no check, 1: odd check, 2: even check)

• bit_order: Bit order (0: LSB first, 1: MSB first)

• invert: Signal inversion (0: normal mode, 1: inversion mode)

• bufsz: buffer size

• reserved: reserved field

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Function interface description

int drv_uart_inst_create(int id, drv_uart_inst_t** inst);

Function: Create UART driver instance.

parameter:

• id: UART interface ID, range [0, KD_HARD_UART_MAX_NUM-1]

• inst: double pointer to store the created instance

Return Value:

• 0: Created successfully

• -1: Invalid parameter

• -2: Invalid UART ID

• -3: Memory allocation failed

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void drv_uart_inst_destroy(drv_uart_inst_t** inst);

Function: Destroy the UART driver instance.

parameter:

• inst: double pointer, pointing to the instance to be destroyed

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size_t drv_uart_read(drv_uart_inst_t* inst, const uint8_t* buffer, size_t size);

Function: Read data from UART.

parameter:

• inst: UART instance

• buffer: Buffer to store read data

• size: Number of bytes to read

Return Value:

• On success: number of bytes actually read

• -1: Invalid parameter

• -2: read error

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size_t drv_uart_write(drv_uart_inst_t* inst, uint8_t* buffer, size_t size);

Function: Write data to UART.

parameter:

• inst: UART instance

• buffer: Data to be written

• size: Number of bytes to write

Return Value:

• On success: number of bytes actually written

• -1: Invalid parameter

• -2: Write error

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int drv_uart_poll(drv_uart_inst_t* inst, int timeout_ms);

Function: Poll UART read availability.

parameter:

• inst: UART instance

• timeout_ms: timeout (milliseconds), -1 means infinite waiting, 0 means non-blocking

Return Value:

• >0: There is data to read

• 0: timeout

• -1: Invalid parameter

• -errno: Polling error (negative errno value)

• -EIO: Device error

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size_t drv_uart_recv_available(drv_uart_inst_t* inst);

Function: Check the number of bytes that can be read.

parameter:

• inst: UART instance

Return Value:

• On success: Number of bytes that can be read

• -1: Invalid parameter

• -2: IOCTL error

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int drv_uart_send_break(drv_uart_inst_t* inst);

Function: Send an interrupt signal on the UART TX line. Force the TX line low for a period of time for special event signaling (such as LIN sync, attention request, soft reset, etc.).

parameter:

• inst: UART instance

Return Value:

• 0: Success

• -1: The instance is invalid or not open

• -2: IOCTL call failed

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int drv_uart_set_config(drv_uart_inst_t* inst, struct uart_configure* cfg);

Function: Set UART configuration.

parameter:

• inst: UART instance

• cfg: configuration structure

Return Value:

• 0: Success

• -1: Invalid parameter

• -2: IOCTL error

Note: This function cannot modify bufsz, please use drv_uart_configure_buffer_size to modify the buffer size.

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int drv_uart_get_config(drv_uart_inst_t* inst, struct uart_configure* cfg);

Function: Get the current UART configuration.

parameter:

• inst: UART instance

• cfg: Structure used to store configuration

Return Value:

• 0: Success

• -1: Invalid parameter

• -2: IOCTL error

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int drv_uart_configure_buffer_size(int id, uint16_t size);

Function: Configure the buffer size of the specified UART device.

parameter:

• id: UART device ID (such as 0 means UART0, 1 means UART1, etc.)

• size: Buffer size to set

Return Value:

• 0: Success

• -1: Invalid UART ID or wrong status

• -2: Device not found or configuration failed

Note: This function should be called before creating the instance.

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int drv_uart_get_id(drv_uart_inst_t *inst);

Function: Get the ID of the UART instance.

parameter:

• inst: UART instance

Return Value:

• When valid: UART ID

• When invalid: -1

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int drv_uart_get_fd(drv_uart_inst_t *inst);

Function: Get the file descriptor of the UART instance.

parameter:

• inst: UART instance

Return Value:

• When valid: file descriptor

• When invalid: -1

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Example

Please refer to src/rtsmart/libs/testcases/rtsmart_hal/test_uart.c

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Things to note

1. The bufsz field of struct uart_configure can only be modified through the drv_uart_configure_buffer_size interface, and bufsz cannot be modified using drv_uart_set_config. The general approach is to first call drv_uart_get_config to obtain the current configuration, modify other parameters except bufsz, and then call drv_uart_set_config.

2. drv_uart_configure_buffer_size must be called before creating the instance.

3. The invert field is not supported on K230.