8. UART operation guide¶

8.1. The Operation Preparation of UART Is as Follows¶

Use the kernel released by SDK。

8.2. Module Compilation¶

The source path is drivers/uart. When users need to access UART devices, they first need to specify the UART source path and header file path in the compilation script. After successful compilation, a library file named libuart.a is generated in the out directory. The library file needs to be specified with the -luart parameter when linking

8.3. Operation Example¶

Step 1:

Call the following interface in the initialization function to implement UART driver registration：

uart_dev_init();

If dma is enabled to receive data, dmac initialization is performed and called in the initialization function：

cvi_dmac_init();

Step 2:

Open the specified UART by calling open from the /dev/ttySN node

Step 3:

After opening UART, ioctl configuration read can be called to read data, write can send data, read can be blocked by select

Step 4:

When UART is not used, close is called to close, after which UART controller no longer receives data from the serial port.

8.4. Action Sample UART API Reference¶

uart_dev_init: UART Device Initialization
uart_suspend: UART Device Suspend
uart_resume: UART Device Wake Up

8.4.1. uart_dev_init¶

【Description】

UART Device Initialization

【Syntax】

int uart_dev_init(void);

【参数】

Parameters	Description	Input / Output
None	None	None

8.4.2. uart_suspend¶

【Description】

UART Device Suspend

【Syntax】

int uart_suspend(void);

【参数】

Parameters	Description	Input / Output
Data	Reserved, passed in NULL	None

【Return Value】

Return Value	Description
0	Success
Others	Failure

8.4.3. uart_resume¶

【Description】

UART Initial wake-up of device。

【Syntax】

int uart_resume(void);

【参数】

Parameters	Description	Input / Output
Data	Not used, passing in NULL	None

【Return Value】

Return Value	Description
0	Success
Others	Failure

8.5. ioctl Configuration Instructions¶

【Description】

After turning on UART, configure UART baud rate, dma reception, blocking reads, wired control, etc. through ioctl.

For example, configure baud rate:

ret = ioctl(fd, CFG_BAUDRATE, 9600);

【Configuration Instructions】

Command Number	Command Code	Parameters	Description
UART_CFG_BAUDRATE	0x101	baud rate	Configure baud rate, UART0 default baud rate 115200; UART1, UART2, UART3 are 9600 Supports a maximum baud rate of 921600
UART_CFG_DMA_RX	0x102	0 or 1	0: Configured as interrupt receiving mode; 1: Configured DMA reception defaults to interrupt type
UART_CFG_DMA_TX	0x103	0 or 1	0: Configured as interrupt receiving mode; 1: Configured DMA reception defaults to interrupt type
UART_CFG_RD_BLOCK	0x104	0 or 1	0: Configure read as non-blocking mode; 1: Configure event blocking read The default is blocking mode;
UART_CFG_ATTR	0x105	0 or 1	Configure check bits, data bits, stop bits, FIFO, CTS/RTS, etc The default is: no check bit, 8 bits of data bit, 1 bit Stop bit, no CTS/RTS. Refer to the header file struct uart_attr
UART_CFG_PRIV	0x110	Custo mization	Drive custom commands