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

UART Module

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

uart.alt()

Change UART pin assignment.

Syntax

uart.alt(on)

Parameters

on:

• 0 use standard pins
• 1 use alternate pins GPIO13 and GPIO15

Returns

nil

uart.on()

Sets the callback function to handle UART events.

Currently only the "data" event is supported.

Syntax

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

Parameters

• method "data", data has been received on the UART
• number/end_char
  • 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
• 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.

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.setup()

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

Syntax

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

Parameters

• id always zero, only one uart supported
• baud one of 300, 600, 1200, 2400, 4800, 9600, 19200, 38400, 57600, 74880, 115200, 230400, 460800, 921600, 1843200, 2686400
• 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 if 0, disable echo, otherwise enable echo

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.write()

Write string or byte to the UART.

Syntax

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

Parameters

• id always 0, only one UART supported
• data1... string or byte to send via UART

Returns

nil

Example

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