UART

[中文]

1 Function Overview

UART (Universal Asynchronous Receiver and Transmitter) is a universal asynchronous receiver/transmitter used to implement full-duplex or half-duplex data exchange between different devices.the BK7258 has three UARTs, with UART0 currently being exclusively used by the CP side (for log output, AP side is prohibited from using it). The AP side only supports the use of UART1 and UART2.

• UART-Related Theoretical Introduction: UART_driver

Note

• 1.UART0 is exclusively reserved for CP side (for log output use, AP side is prohibited from using it)；

• 2.AP side is only allowed to use UART1 and UART2, and no other UARTs.

2 code path

• demo path：

  cp\components\bk_cli\cli_uart.c

• source code path：

  cp\middleware\driver\uart\uart_driver.c

3 uart related macro configuration

NAME	Description	File	value
CONFIG_UART0	UART0 Enable Configuration	cp\middleware\soc\bk7258\bk7258.defconfig	y
CONFIG_UART_PRINT_PORT	Configure the UART port for printing log output	cp\middleware\soc\bk7258\bk7258.defconfig	0
CONFIG_PRINTF_BUF_SIZE	Configure the buffer size for printing log output	cp\middleware\soc\bk7258\bk7258.defconfig	256
CONFIG_KFIFO_SIZE	Configure the software FIFO size for UART	cp\middleware\soc\bk7258\bk7258.defconfig	128
CONFIG_UART_ERR_INTERRUPT	Enable UART error interrupt	cp\middleware\soc\bk7258\bk7258.defconfig	y
CONFIG_UART_TX_DMA	copy data from RAM to UART FIFO	cp\middleware\soc\bk7258\bk7258.defconfig	n
CONFIG_UART_RX_DMA	copy data from UART FIFO to RAM	cp\middleware\soc\bk7258\bk7258.defconfig	n
UART_RX_DMA_KFIFO_SIZE	Configure the KFIFO size for UART RX DMA	cp\middleware\soc\bk7258\bk7258.defconfig	128

4 UART PIN Descriptions

• UART0 corresponds to uart0 on the development board, with the following hardware pins:

  UART0 function	group 0
  UART0_TX	GPIO11
  UART0_RX	GPIO10

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5 UART demo configuration

• The supported commands for “demo” are as follows:

  Command		Param	Description
  uart_driver {init|deinit}		{init|deinit}:	init/deinit the uart resoure common
  uart {id} init [baud_rate] [data_bits] [parity] [stop_bits] [flow_ctrl] [src_clk] [rx_dma_en] [tx_dma_en]		{id}:uart id,value range 1 ~ 2	init uart and set working parameters
  		{baud_rate}:uart baud rate
  		{data_bits}: support value range 5 ~ 8 bits
  		{parity}: support parity mode
  		{stop_bits}:the stop bits len
  		{flow_ctrl}: not support flow ctrl
  		{src_clk}:uart working clock source
  		{rx_dma_en}: enable uart rx dma
  		{tx_dma_en}: enable uart tx dma
  uart_config {id}	baud_rate {value}	{value}:support baud rate	set uart working parameters
  	data_bits {value}	{value}:support value range 5 ~ 8 bits
  	parity {value}	{value}:support parity none、 odd、 even
  	stop_bits {value}	{value}:support 1 or 2 bits
  	flow_ctrl {value}	{value}:support 0 or 1
  	rx_thresh {value}	{value}:support value range 0 ~ 255 bits
  	tx_thresh {value}	{value}:support value range 0 ~ 255 bits
  	rx_timeout{value}	{value}:support value range 0 ~ 3 bits
  uart_int {id} {enable|disable|reg} {tx|rx}		{id}:uart id,value range 1 ~ 2	enable|disable uart tx|rx interrupt and register uart tx|rx handler
  		{enable|disable}:enable|disable tx|rx interrupt
  		{tx|rx}: register tx|rx interrupt handler
  uart {id} {read|write} {length}		{id}:uart id,value range 1 ~ 2	read specified length of data through uart
  		{read|write}: read|write operation
  		{length}: length to be read|write

Note

-1.The UART module’s clock source is 26M Hz, and the baud rate is derived from this 26M Hz clock source.；

-2.The calculation method is “divisor = (clock source value / baud rate) - 1”. The software then sets the divisor value to the UART register.；

-3.For example: If we want to set the baud rate to 115200, the divisor value is calculated as follows: (26000000 / 115200) - 1 = 224. The software sets 224 as the value for the UART register. Therefore, if we want to set a different baud rate, we only need to calculate the divisor value and set it to the UART register. (Note: The divisor value should be an integer type)