# Alcor6L/eLua/uart

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
## uart.setup

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

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.
* 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

Read a single character from the serial port
* 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

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

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

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.
* 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.