UART Baudrate Interface

Typedefs
typedef enum ALT_16550_BAUDRATE_e	ALT_16550_BAUDRATE_t

Enumerations
enum	ALT_16550_BAUDRATE_e {   ALT_16550_BAUDRATE_50 = 50 , ALT_16550_BAUDRATE_75 = 75 , ALT_16550_BAUDRATE_150 = 150 , ALT_16550_BAUDRATE_300 = 300 ,   ALT_16550_BAUDRATE_600 = 600 , ALT_16550_BAUDRATE_900 = 900 , ALT_16550_BAUDRATE_1200 = 1200 , ALT_16550_BAUDRATE_1800 = 1800 ,   ALT_16550_BAUDRATE_2400 = 2400 , ALT_16550_BAUDRATE_3600 = 3600 , ALT_16550_BAUDRATE_4800 = 4800 , ALT_16550_BAUDRATE_7200 = 7200 ,   ALT_16550_BAUDRATE_9600 = 9600 , ALT_16550_BAUDRATE_14400 = 14400 , ALT_16550_BAUDRATE_19200 = 19200 , ALT_16550_BAUDRATE_28800 = 28800 ,   ALT_16550_BAUDRATE_38400 = 38400 , ALT_16550_BAUDRATE_57600 = 57600 , ALT_16550_BAUDRATE_115200 = 115200 }

Functions
ALT_STATUS_CODE	alt_16550_baudrate_get (ALT_16550_HANDLE_t *handle, uint32_t *baudrate)
ALT_STATUS_CODE	alt_16550_baudrate_set (ALT_16550_HANDLE_t *handle, uint32_t baudrate)
ALT_STATUS_CODE	alt_16550_divisor_get (ALT_16550_HANDLE_t *handle, uint32_t *divisor)
ALT_STATUS_CODE	alt_16550_divisor_set (ALT_16550_HANDLE_t *handle, uint32_t divisor)

Detailed Description

This group of APIs allows for the configuration of the UART's baudrate generation related functions.

The UART baudrate is determined by dividing the ALT_CLK_L4_SP clock with the configured divisor.

Typedef Documentation

ALT_16550_BAUDRATE_t

typedef enum ALT_16550_BAUDRATE_e ALT_16550_BAUDRATE_t

This enumeration lists out the common baudrates used with modem and serial ports. Not every baudrate is available for the UART due to the limits of the serial clock frequency and divisor value.

Enumeration Type Documentation

ALT_16550_BAUDRATE_e

enum ALT_16550_BAUDRATE_e

This enumeration lists out the common baudrates used with modem and serial ports. Not every baudrate is available for the UART due to the limits of the serial clock frequency and divisor value.

Enumerator
ALT_16550_BAUDRATE_50	50 bps baudrate.
ALT_16550_BAUDRATE_75	75 bps baudrate.
ALT_16550_BAUDRATE_150	150 bps baudrate.
ALT_16550_BAUDRATE_300	300 bps baudrate.
ALT_16550_BAUDRATE_600	600 bps baudrate.
ALT_16550_BAUDRATE_900	900 bps baudrate.
ALT_16550_BAUDRATE_1200	1200 bps baudrate.
ALT_16550_BAUDRATE_1800	1800 bps baudrate.
ALT_16550_BAUDRATE_2400	2400 bps baudrate.
ALT_16550_BAUDRATE_3600	3600 bps baudrate.
ALT_16550_BAUDRATE_4800	4800 bps baudrate.
ALT_16550_BAUDRATE_7200	7200 bps baudrate.
ALT_16550_BAUDRATE_9600	9600 bps baudrate.
ALT_16550_BAUDRATE_14400	14400 bps baudrate.
ALT_16550_BAUDRATE_19200	19200 bps baudrate.
ALT_16550_BAUDRATE_28800	28800 bps baudrate.
ALT_16550_BAUDRATE_38400	38400 bps baudrate.
ALT_16550_BAUDRATE_57600	57600 bps baudrate.
ALT_16550_BAUDRATE_115200	115200 bps baudrate.

Function Documentation

alt_16550_baudrate_get()

ALT_STATUS_CODE alt_16550_baudrate_get	(	ALT_16550_HANDLE_t *	handle,
		uint32_t *	baudrate
	)

Gets the baudrate for the UART.

This is done by calculating the baudrate from the divisor and the serial clock. The reported baudrate may not correspond exactly to the request baudrate.

Parameters

handle	The UART device handle.
baudrate	[out] Pointer to an output paramter that contains the current baudrate of the UART.

Return values

ALT_E_SUCCESS	The operation was successful.
ALT_E_ERROR	The operation failed.
ALT_E_BAD_ARG	The given UART device handle is invalid.

alt_16550_baudrate_set()

ALT_STATUS_CODE alt_16550_baudrate_set	(	ALT_16550_HANDLE_t *	handle,
		uint32_t	baudrate
	)

Sets the baudrate for the UART. This change will take effect when the UART moves from disabled to enabled.

This is done by calculating the correct divisor using the request baudrate and the known serial clock.

Parameters

handle	The UART device handle.
baudrate	The requested baudrate for the UART.

Return values

ALT_E_SUCCESS	The operation was successful.
ALT_E_ERROR	The operation failed.
ALT_E_BAD_ARG	The given UART device handle is invalid.
ALT_E_ARG_RANGE	The given baudrate is not possible due to limitations of the baudrate divisor and/or serial clock.

alt_16550_divisor_get()

ALT_STATUS_CODE alt_16550_divisor_get	(	ALT_16550_HANDLE_t *	handle,
		uint32_t *	divisor
	)

Gets the baudrate divisor for the UART.

The baudrate is determined by the following formula:

• Baudrate = (serial clock frequency) / (16 * divisor)

Parameters

handle	The UART device handle.
divisor	[out] Pointer to an output parameter that contains the current divisor used for baudrate generation.

Return values

ALT_E_SUCCESS	The operation was successful.
ALT_E_ERROR	The operation failed.
ALT_E_BAD_ARG	The given UART device handle is invalid.

alt_16550_divisor_set()

ALT_STATUS_CODE alt_16550_divisor_set	(	ALT_16550_HANDLE_t *	handle,
		uint32_t	divisor
	)

Sets the baudrate divisor for the UART. This change will take effect when the UART moves from disabled to enabled.

The baudrate is determined by the following formula:

• Baudrate = (serial clock frequency) / (16 * divisor)

Parameters

handle	The UART device handle.
divisor	The specified divisor value to use for baudrate generation. Valid values are 1 - 65535.

Return values

ALT_E_SUCCESS	The operation was successful.
ALT_E_ERROR	The operation failed.
ALT_E_BAD_ARG	The given UART identifier is invalid or the specified divisor is not supported by the UART.