The UART drivers used in QMK have a set of common functions to allow portability between MCUs.
Currently, this driver does not support enabling hardware flow control (the RTS
and CTS
pins) if available, but may do so in future.
No special setup is required - just connect the RX
and TX
pins of your UART device to the opposite pins on the MCU:
MCU | TX |
RX |
CTS |
RTS |
---|---|---|---|---|
ATmega16/32U2 | D3 |
D2 |
D7 |
D6 |
ATmega16/32U4 | D3 |
D2 |
D5 |
B7 |
AT90USB64/128 | D3 |
D2 |
n/a | n/a |
ATmega32A | D1 |
D0 |
n/a | n/a |
ATmega328/P | D1 |
D0 |
n/a | n/a |
You'll need to determine which pins can be used for UART -- as an example, STM32 parts generally have multiple UART peripherals, labeled USART1, USART2, USART3 etc.
To enable UART, modify your board's halconf.h
to enable the serial driver:
#define HAL_USE_SERIAL TRUE
Then, modify your board's mcuconf.h
to enable the peripheral you've chosen, for example:
#undef STM32_SERIAL_USE_USART2
#define STM32_SERIAL_USE_USART2 TRUE
Configuration-wise, you'll need to set up the peripheral as per your MCU's datasheet -- the defaults match the pins for a Proton-C, i.e. STM32F303.
config.h override |
Description | Default Value |
---|---|---|
#define SERIAL_DRIVER |
USART peripheral to use - USART1 -> SD1 , USART2 -> SD2 etc. |
SD1 |
#define SD1_TX_PIN |
The pin to use for TX | A9 |
#define SD1_TX_PAL_MODE |
The alternate function mode for TX | 7 |
#define SD1_RX_PIN |
The pin to use for RX | A10 |
#define SD1_RX_PAL_MODE |
The alternate function mode for RX | 7 |
#define SD1_CTS_PIN |
The pin to use for CTS | A11 |
#define SD1_CTS_PAL_MODE |
The alternate function mode for CTS | 7 |
#define SD1_RTS_PIN |
The pin to use for RTS | A12 |
#define SD1_RTS_PAL_MODE |
The alternate function mode for RTS | 7 |
Initialize the UART driver. This function must be called only once, before any of the below functions can be called.
uint32_t baud
The baud rate to transmit and receive at. This may depend on the device you are communicating with. Common values are 1200, 2400, 4800, 9600, 19200, 38400, 57600, and 115200.
Transmit a single byte.
uint8_t c
The byte (character) to send, from 0 to 255.
Receive a single byte.
The byte read from the receive buffer.
Return whether the receive buffer contains data. Call this function to determine if uart_getchar()
will return meaningful data.
true
if the receive buffer length is non-zero.