nodemcu-firmware/docs/en/modules/uart.md

UART Module

Since	Origin / Contributor	Maintainer	Source
2014-12-22	Zeroday	Zeroday	uart.c

The UART (Universal asynchronous receiver/transmitter) module allows configuration of and communication over the UART serial port.

The default setup for the console uart is controlled by build-time settings. The default uart for console is UART0. The default rate is 115,200 bps. In addition, auto-baudrate detection is enabled for the first two minutes 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.

For other uarts, you should call uart.setup and uart.start to get them working.

uart.on()

Sets the callback function to handle UART events.

Syntax

uart.on([id], method, [number/end_char], [function], [run_input])

Parameters

• id uart id, default value is uart num of the console.
• method "data", data has been received on the UART. "error", error occurred on the UART.
• number/end_char. Only for event data.
  • if pass in a number n<255, the callback will called when n chars are received.
  • if n=0, will receive every char in buffer.
  • if pass in a one char string "c", the callback will called when "c" is encounterd, or max n=255 received.
• function callback function.
  • event "data" has a callback like this: function(data) end
  • event "error" has a callback like this: function(err) end. err could be one of "out_of_memory", "break", "rx_error".
• run_input 0 or 1. Only for "data" event on console uart. 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.

To unregister the callback, provide only the "data" parameter.

Returns

nil

Example

-- when 4 chars is received.
uart.on("data", 4,
  function(data)
	print("receive from uart:", data)
	if data=="quit" then
	  uart.on("data") -- unregister callback function
	end
end, 0)
-- when '\r' is received.
uart.on("data", "\r",
  function(data)
	print("receive from uart:", data)
	if data=="quit\r" then
	  uart.on("data") -- unregister callback function
	end
end, 0)

-- uart 2
uart.on(2, "data", "\r",
  function(data)
	print("receive from uart:", data)
  end)
  
-- error handler
uart.on(2, "error",
  function(data)
	print("error from uart:", data)
  end)

uart.setup()

(Re-)configures the communication parameters of the UART.

Syntax

uart.setup(id, baud, databits, parity, stopbits, echo_or_pins)

Parameters

• id uart id
• baud one of 300, 600, 1200, 2400, 4800, 9600, 19200, 38400, 57600, 74880, 115200, 230400, 256000, 460800, 921600, 1843200, 3686400
• databits one of 5, 6, 7, 8
• parity uart.PARITY_NONE, uart.PARITY_ODD, or uart.PARITY_EVEN
• stopbits uart.STOPBITS_1, uart.STOPBITS_1_5, or uart.STOPBITS_2
• echo_or_pins
  • for console uart, this should be a int. if 0, disable echo, otherwise enable echo
  • for others, this is a table:
    • tx int. TX pin. Required
    • rx int. RX pin. Required
    • cts in. CTS pin. Optional
    • rts in. RTS pin. Optional
    • tx_inverse boolean. Inverse TX pin. Default: false
    • rx_inverse boolean. Inverse RX pin. Default: false
    • cts_inverse boolean. Inverse CTS pin. Default: false
    • rts_inverse boolean. Inverse RTS pin. Default: false
    • flow_control int. Combination of uart.FLOWCTRL_NONE, uart.FLOWCTRL_CTS, uart.FLOWCTRL_RTS. Default: uart.FLOWCTRL_NONE

Returns

configured baud rate (number)

Example

-- configure for 9600, 8N1, with echo
uart.setup(0, 9600, 8, uart.PARITY_NONE, uart.STOPBITS_1, 1)

uart.setup(2, 115200, 8, uart.PARITY_NONE, uart.STOPBITS_1, {tx = 16, rx = 17})

uart.start()

Start the UART. You do not need to call start() on the console uart.

Syntax

uart.start(id)

Parameters

• id uart id, except console uart

Returns

Boolean. true if uart is started.

uart.stop()

Stop the UART. You should not call stop() on the console uart.

Syntax

uart.stop(id)

Parameters

• id uart id, except console uart

Returns

nil

uart.write()

Write string or byte to the UART.

Syntax

uart.write(id, data1 [, data2, ...])

Parameters

• id uart id
• data1... string or byte to send via UART

Returns

nil

Example

uart.write(0, "Hello, world\n")