57 lines
2.4 KiB
Markdown
57 lines
2.4 KiB
Markdown
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avr-uart
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========
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An interrupt driven UART Library for 8-bit AVR microcontrollers
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Maintained by Andy Gock
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https://github.com/andygock/avr-uart
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Derived from original library by Peter Fleury
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Interrupt UART library using the built-in UART with transmit and receive circular buffers.
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An interrupt is generated when the UART has finished transmitting or
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receiving a byte. The interrupt handling routines use circular buffers
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for buffering received and transmitted data.
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## Setting up
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The `UART_RXn_BUFFER_SIZE` and `UART_TXn_BUFFER_SIZE` constants define
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the size of the circular buffers in bytes. Note that these constants must be a power of 2.
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You may need to adapt this constants to your target and your application by adding to your
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compiler options:
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-DUART_RXn_BUFFER_SIZE=nn -DUART_TXn_BUFFER_SIZE=nn
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`RXn` and `TXn` refer to UART number, for UART3 with 128 byte buffers, add:
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-DUART_RX3_BUFFER_SIZE=128 -DUART_TX3_BUFFER_SIZE=128
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UART0 is always enabled by default, to enable the other available UARTs, add the following
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to your compiler options (or symbol options), for the relevant USART number:
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-DUSART1_ENABLED -DUSART2_ENABLED -DUSART3_ENABLED
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To enable large buffer support (over 256 bytes, up to 2^16 bytes) use:
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-DUSARTn_LARGE_BUFFER
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Where n = USART number.
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Supports AVR devices with up to 4 hardware USARTs.
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## Documentation
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Doxygen based documentation will be coming soon.
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## Notes
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### Buffer overflow behaviour
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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.
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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.
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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.
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