137 lines
3.8 KiB
Markdown
137 lines
3.8 KiB
Markdown
# UART Module
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| Since | Origin / Contributor | Maintainer | Source |
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| :----- | :-------------------- | :---------- | :------ |
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| 2014-12-22 | [Zeroday](https://github.com/funshine) | [Zeroday](https://github.com/funshine) | [uart.c](../../../app/modules/uart.c)|
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The [UART](https://en.wikipedia.org/wiki/Universal_asynchronous_receiver/transmitter) (Universal asynchronous receiver/transmitter) module allows configuration of and communication over the UART serial port.
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The default setup for the uart is controlled by build-time settings. The default rate is 115,200 bps. In addition, auto-baudrate detection is enabled for the first two minutes
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after platform boot. This will cause a switch to the correct baud rate once a few characters are received. Auto-baudrate detection is disabled when `uart.setup` is called.
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## uart.alt()
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Change UART pin assignment.
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#### Syntax
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`uart.alt(on)`
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#### Parameters
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`on`
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- 0 for standard pins
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- 1 to use alternate pins GPIO13 and GPIO15
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#### Returns
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`nil`
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## uart.on()
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Sets the callback function to handle UART events.
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Currently only the "data" event is supported.
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#### Syntax
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`uart.on(method, [number/end_char], [function], [run_input])`
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#### Parameters
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- `method` "data", data has been received on the UART
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- `number/end_char`
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- if n=0, will receive every char in buffer
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- if n<255, the callback is called when n chars are received
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- if one char "c", the callback will be called when "c" is encountered, or max n=255 received
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- `function` callback function, event "data" has a callback like this: `function(data) end`
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- `run_input` 0 or 1. If 0, input from UART will not go into Lua interpreter, can accept binary data. If 1, input from UART will go into Lua interpreter, and run.
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To unregister the callback, provide only the "data" parameter.
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#### Returns
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`nil`
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#### Example
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```lua
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-- when 4 chars is received.
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uart.on("data", 4,
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function(data)
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print("receive from uart:", data)
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if data=="quit" then
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uart.on("data") -- unregister callback function
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end
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end, 0)
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-- when '\r' is received.
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uart.on("data", "\r",
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function(data)
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print("receive from uart:", data)
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if data=="quit\r" then
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uart.on("data") -- unregister callback function
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end
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end, 0)
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```
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## uart.setup()
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(Re-)configures the communication parameters of the UART.
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#### Syntax
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`uart.setup(id, baud, databits, parity, stopbits, echo)`
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#### Parameters
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- `id` always zero, only one uart supported
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- `baud` one of 300, 600, 1200, 2400, 4800, 9600, 19200, 38400, 57600, 74880, 115200, 230400, 256000, 460800, 921600, 1843200, 3686400
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- `databits` one of 5, 6, 7, 8
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- `parity` `uart.PARITY_NONE`, `uart.PARITY_ODD`, or `uart.PARITY_EVEN`
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- `stopbits` `uart.STOPBITS_1`, `uart.STOPBITS_1_5`, or `uart.STOPBITS_2`
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- `echo` if 0, disable echo, otherwise enable echo
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#### Returns
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configured baud rate (number)
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#### Example
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```lua
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-- configure for 9600, 8N1, with echo
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uart.setup(0, 9600, 8, uart.PARITY_NONE, uart.STOPBITS_1, 1)
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```
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## uart.getconfig()
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Returns the current configuration parameters of the UART.
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#### Syntax
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`uart.getconfig(id)`
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#### Parameters
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- `id` always zero, only one uart supported
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#### Returns
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Four values as follows:
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- `baud` one of 300, 600, 1200, 2400, 4800, 9600, 19200, 38400, 57600, 74880, 115200, 230400, 256000, 460800, 921600, 1843200, 3686400
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- `databits` one of 5, 6, 7, 8
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- `parity` `uart.PARITY_NONE`, `uart.PARITY_ODD`, or `uart.PARITY_EVEN`
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- `stopbits` `uart.STOPBITS_1`, `uart.STOPBITS_1_5`, or `uart.STOPBITS_2`
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#### Example
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```lua
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print (uart.getconfig(0))
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-- prints 9600 8 0 1 for 9600, 8N1
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```
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## uart.write()
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Write string or byte to the UART.
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#### Syntax
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`uart.write(id, data1 [, data2, ...])`
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#### Parameters
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- `id` always 0, only one UART supported
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- `data1`... string or byte to send via UART
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#### Returns
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`nil`
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#### Example
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```lua
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uart.write(0, "Hello, world\n")
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```
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