Alcor6L/eLua/uart

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Overview[edit]

This module contains functions for accessing the serial ports (UARTs) of the eLua CPU.

UART ids can be

  • 0, 1, etc for physical serial ports,
  • uart.VUART0 to uart.VUART7 if virtual UART support is enabled in eLua, or
  • 176 for the USB CDC serial port.

Functions[edit]

uart.setup[edit]

Setup the serial port. Note that you can't call this function for a virtual UART.

baud = uart.setup( id, baud, databits, parity, stopbits )
  • id - the ID of the serial port
  • baud - serial baud rate
  • databits - number of data bits
  • parity - parity type, can be uart.PAR_EVEN, uart.PAR_ODD or uart.PAR_NONE
  • stopbits - the number of stop bits, can be uart.STOP_1, uart.STOP_1_5 or uart.STOP_2

Returns:

  • baud - The actual baud rate set on the serial port. Depending on the hardware, this might have a different value than the baud parameter

uart.write[edit]

Write one or more strings or 8-bit integers (raw data) to the serial port. If writing raw data, its value (represented by an integer) must be between 0 and 255.

uart.write( id, data1, [data2], ..., [datan] )
  • id - the ID of the serial port.
  • data1 - the first string/8-bit integer to write.
  • data2 (optional) - the second string/8-bit integer to write.
  • datan (optional) - the n-th string/8-bit integer to write.

uart.getchar[edit]

Read a single character from the serial port

str = uart.getchar( id, [timeout], [timer_id] )
  • id - the ID of the serial port
  • timeout (optional) - timeout of the operation, can be either uart.NO_TIMEOUT or 0 for non-blocking operation, uart.INF_TIMEOUT for blocking operation, or a positive number that specifies the timeout in microseconds. The default value of this argument is uart.INF_TIMEOUT.
  • timer_id (optional) - the ID of the timer used for measuring the timeout. If not specified it defaults to the system timer.

Returns:

  • str - The character read from the serial port as a string, or the empty string it timeout occured while waiting for the character.

uart.read[edit]

Reads one or more characters from the serial port according to a format specifier

str = uart.read( id, format, [timeout], [timer_id] )
  • id - the ID of the serial port
  • format - format of data to read. This can be either:
    • '*l' - read until an end of line character (a \n) is found (the \n is not returned) or a timeout occurs.
    • '*n' - read an integer. The integer can optionally have a sign. Reading continues until the first non-digit character is detected or a timeout occurs. This is the only case in which read returns a number instead of an integer.
    • '*s' - read until a spacing character (like a space or a TAB) is found (the spacing character is not returned) or a timeout occurs.
    • a positive number - read at most this many characters before returning (reading can stop earlier if a timeout occurs).
  • timeout (optional) - timeout of the operation, can be either uart.NO_TIMEOUT or 0 for non-blocking operation, uart.INF_TIMEOUT for blocking operation, or a positive number that specifies the timeout in microseconds. The default value of this argument is uart.INF_TIMEOUT.
  • timer_id (optional) - the ID of the timer used for measuring the timeout. If not specified it defaults to the system timer.

Returns:

  • str - The data read from the serial port as a string (or as a number if format is '*n'). If a timeout occures, only the data read before the timeout is returned. If the function times out while trying to read the first character, the empty string is returned

uart.set_buffer[edit]

Sets the size of the UART buffer. Note that calling this function with bufsize = 0 for a virtual UART is not allowed.

uart.set_buffer( id, bufsize )
  • id - the ID of the serial port
  • bufsize - the size of the buffer (must be a power of 2) or 0 to disable buffering on the specified UART.

uart.set_flow_control[edit]

Sets the flow control on the UART. Note that this function works only on physical ports, it will return an error if called on a virtual UART.

uart.set_flow_control( id, type )
  • id - the ID of the serial port.
  • type - the flow control type, it can be:
    • uart.FLOW_NONE (no flow control),
    • uart.FLOW_RTS for RTS flow control,
    • uart.FLOW_CTS for CTS flow control or
    • uart.FLOW_RTS + uart.FLOW_CTS for full RTS/CTS flow control.