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UART ​

UART Serial API.

API functions for bidirectional Asynchronous serial communications

Sysprops ​

syspropdescription
gpio_txRX GPIO
gpio_rxTX GPIO
gpio_rtsRTS GPIO
gpio_ctsCTS GPIO

Functions Overview ​

Name
CW_DRIVER_FUNCuart_config(int hDev, uint32_t baudrate, uint8_t bits, uint8_t stop, uint8_t parity)
configure baudrate and hardware protocol for the UART.
CW_DRIVER_FUNCuart_write(int hDev, char * buf, size_t buflen, uint32_t timeout_ms)
write a character sequence over the UART
CW_DRIVER_FUNCuart_read(int hDev, char * buf, size_t buflen, uint32_t timeout_ms)
read a character sequence from the UART

Defines ​

Name
UART_IOCTL_SEND_BREAK
UART_IOCTL_HALF_DUPLEX
UART_STOPBITS_1
UART_STOPBITS_2
UART_PARITY_NONE
UART_PARITY_ODD
UART_PARITY_EVEN

Function Details ​

function uart_config ​

cpp
CW_DRIVER_FUNC uart_config(
    int hDev,
    uint32_t baudrate,
    uint8_t bits,
    uint8_t stop,
    uint8_t parity
)

configure baudrate and hardware protocol for the UART.

Parameters:

  • hDev device handle as returned by open(const char*)
  • baudrate desired baudrate. the peripheral driver documentation should be consulted for supported baudrates
  • bits databits in the UART protocol, ususally 8
  • stop number of stop-bits in the UART protocol. since 1.5 stop bits is no longer used in modern devices, it is not supported here.
  • parity 0 for no parity, 1 for odd and 2 for even parity

function uart_write ​

cpp
CW_DRIVER_FUNC uart_write(
    int hDev,
    char * buf,
    size_t buflen,
    uint32_t timeout_ms
)

write a character sequence over the UART

Parameters:

  • hDev device handle as returned by open(const char*)
  • buf pointer to a char buffer. the buffer is not copied in the function, so it needs to be valid until the function returns.
  • buflen length of the passed buffer.
  • timeout_ms timeout in milliseconds to wait for the buffer to be transmitted

Return: 0 on successful write.

the function acts as blocking during a write to simplify the application architecture.

function uart_read ​

cpp
CW_DRIVER_FUNC uart_read(
    int hDev,
    char * buf,
    size_t buflen,
    uint32_t timeout_ms
)

read a character sequence from the UART

Parameters:

  • hDev device handle as returned by open(const char*)
  • buf buffer to hold the received characters.
  • buflen length of the provided buffer
  • timeout_ms timeout in milliseconds to wait for buflen characters to be returned

Return: number of characters read

the function will return after

  • the timeout has passed.
  • n > 0 characters have been received, followed by a timeout of at least 2 character-times.
  • the passed buffer is full.

Macros Documentation ​

define UART_IOCTL_SEND_BREAK ​

cpp
#define UART_IOCTL_SEND_BREAK (0x0F01)

define UART_IOCTL_HALF_DUPLEX ​

cpp
#define UART_IOCTL_HALF_DUPLEX (0x0F02)

define UART_STOPBITS_1 ​

cpp
#define UART_STOPBITS_1 (1U)

define UART_STOPBITS_2 ​

cpp
#define UART_STOPBITS_2 (2U)

define UART_PARITY_NONE ​

cpp
#define UART_PARITY_NONE (0U)

define UART_PARITY_ODD ​

cpp
#define UART_PARITY_ODD (1U)

define UART_PARITY_EVEN ​

cpp
#define UART_PARITY_EVEN (2U)