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UART Hal Interface Documentation

Hardware Introduction

The K230 integrates five UART (Universal Asynchronous Receiver-Transmitter) hardware modules internally, among which the rtsmart system occupies one serial port (occupying serial port 0 by default), and other serial ports are available for users.

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Data Structure Description

struct uart_configure

UART configuration structure, containing the following members:

• baud_rate: baud rate

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

• stop_bits: number of stop bits (0-3 corresponding to 1-4 stop bits)

• parity: parity bit (0: no parity, 1: odd parity, 2: even parity)

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

• invert: signal inversion (0: normal mode, 1: inverted 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: Creates a UART driver instance.

Parameters:

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

• inst: Double pointer, used 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: Destroys a UART driver instance.

Parameters:

• 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: Reads data from UART.

Parameters:

• inst: UART instance

• buffer: Buffer to store the 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: Writes data to UART.

Parameters:

• 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: Polls UART for read availability.

Parameters:

• inst: UART instance

• timeout_ms: Timeout in milliseconds, -1 means infinite wait, 0 means non-blocking

Return Value:

• >0: Data is available 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: Checks the number of bytes available to read.

Parameters:

• inst: UART instance

Return Value:

• On success: Number of bytes available to read

• -1: Invalid parameter

• -2: IOCTL error

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int drv_uart_send_break(drv_uart_inst_t* inst);

Function: Sends a break signal on the UART TX line. Forces the TX line low for a period of time, used for special event signals (such as LIN sync, attention request, soft reset, etc.).

Parameters:

• inst: UART instance

Return Value:

• 0: Success

• -1: Invalid instance or not opened

• -2: IOCTL call failed

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

Function: Sets UART configuration.

Parameters:

• 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: Gets the current UART configuration.

Parameters:

• inst: UART instance

• cfg: Structure used to store the 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: Configures the buffer size for the specified UART device.

Parameters:

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

• size: Buffer size to be set

Return Value:

• 0: Success

• -1: Invalid UART ID or state error

• -2: Device not found or configuration failed

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

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int drv_uart_get_id(drv_uart_inst_t *inst);

Function: Gets the ID of the UART instance.

Parameters:

• inst: UART instance

Return Value:

• On valid: UART ID

• On invalid: -1

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int drv_uart_get_fd(drv_uart_inst_t *inst);

Function: Gets the file descriptor of the UART instance.

Parameters:

• inst: UART instance

Return Value:

• On valid: File descriptor

• On invalid: -1

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Example

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

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Notes

1. The bufsz field of struct uart_configure can only be modified through the drv_uart_configure_buffer_size interface; using drv_uart_set_config cannot modify bufsz. The general approach is to first call drv_uart_get_config to obtain the current configuration, modify parameters other than 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 the K230.