An interrupt driven UART Library for 8-bit AVR microcontrollers
Maintained by Andy Gock
Derived from original library by Peter Fleury.
Interrupt driven UART library using the built-in UART with circular transmit and receive buffers.
An interrupt is generated when the UART has finished transmitting or receiving a byte. The interrupt handling routines use circular buffers for buffering received and transmitted data.
UART_TXn_BUFFER_SIZE symbols define
the size of the circular buffers in bytes. These values must be a power of 2.
You may need to adapt this symbols to your target and your application by adding into your compiler options:
TXn refer to the UART number, for UART3 with 128 byte buffers, add:
UART0 is always enabled by default, to enable the other available UARTs, add the following to your compiler's symbol options for the relevant UART (also known as USART) number.
-DUSART1_ENABLED -DUSART2_ENABLED -DUSART3_ENABLED
To enable large buffer support (over 256 bytes, up to 2^15 bytes) use:
Where n = USART number. The maximum buffer size is 32768.
This library supports AVR devices with up to 4 hardware USARTs.
AVR/GNU C compiler requires the
Doxygen based documentation can be viwed at:
- HTML: https://andygock.github.io/avr-uart-documentation/html/index.html
- PDF: https://andygock.github.io/avr-uart-documentation/latex/refman.pdf
- RTF: https://andygock.github.io/avr-uart-documentation/rtf/refman.rtf
Buffer overflow behaviour
When the RX circular buffer is full, and it receives further data from the UART, a buffer overflow condition occurs. Any new data is dropped. The RX buffer must be read before any more incoming data from the UART is placed into the RX buffer.
If the TX buffer is full, and new data is sent to it using one of the
uartN_put*() functions, this function will loop and wait until the buffer is not full any more. It is important to make sure you have not disabled your UART transmit interrupts (
TXEN*) elsewhere in your application (e.g with
cli()) before calling the
uartN_put*() functions, as the application will lock up. The UART interrupts are automatically enabled when you use the
uartN_init() functions. This is probably not the idea behaviour, I'll probably fix this some time.
For now, make sure
TXEN* interrupts are enabled when calling
uartN_put*() functions. This should not be an issue unless you have code elsewhere purposely turning it off.