Serial Link Test Program
------------------------

"sertest" is a test program for checking the integrity of serial port links.


Features:
  - Sends and/or receives variable length messages,
  - Data is generated randomly, using a seed for reproducability (seed zero
    means pseudo-random),
  - Received data is verified against the expected data,
  - Supports unidirectional links:
      - master transmits,
      - slave receives.
  - Supports bidirectional links:
      - master transmits,
      - slave receives and retransmits,
      - master receives.
  - Supports chained multi-link configurations:
      - master transmits,
      - slave 1..n receive and retransmit,
      - master (closed ring) or slave n+1 (open ring) receives.
  - When chaining multiple links, the received data bytes are incremented by
    one before retransmission.
  

Usage:

    sertest: [options] <device> [<device2>]

    Valid options are:
	-h, --help       Display this usage information
	--master         Use master mode
	--slave          Use slave mode (default)
	--chain          Master and slave(s) are daisy chained
	--icount         Only print icount
	-i, --seed       Initial seed (zero is pseudorandom)
	-l, --len        Maximum message length (default 256, must be <= 4096)
	-s, --speed      Serial speed
	-v, --verbose    Enable verbose mode

    If one device is specified, it is used for bidirectional communication.
    If two devices are specified, the first device is used for output, and
    the second device is used for input.

    Use "CTRL-C" to print transfer statistics, "CTRL-\" to quit.


Examples:

  * Unidirectional test, transmitting from ttyS0 to ttyS1:

	sertest --slave  /dev/ttyS1
	sertest --master /dev/ttyS0 (somewhere else)

    Wiring:
        TXD0 -> RXD1

  * Bidirectional test, transmitting from ttyS0 to ttyS1 and back:

	sertest --slave  --chain /dev/ttyS1
	sertest --master --chain /dev/ttyS0 (somewhere else)

    Wiring ("null modem"):
        TXD0 -> RXD1
        TXD1 -> RXD0

  * Bidirectional test, using two fifos instead of real serial ports:

	mkfifo /tmp/fifo1
	mkfifo /tmp/fifo2
	sertest --slave --chain  /tmp/fifo2 /tmp/fifo1
	sertest --master --chain /tmp/fifo1 /tmp/fifo2 (in another window)

  * Ring chain test, ttyS0 -> ttyS1 -> ttyS2 -> ttyS3 -> ttyS0:

	sertest --slave  --chain /dev/ttyS3
	sertest --slave  --chain /dev/ttyS2 (somewhere else)
	sertest --slave  --chain /dev/ttyS1 (somewhere else)
	sertest --master --chain /dev/ttyS0 (somewhere else)

    Wiring:
        TXD0 -> RXD1
        TXD1 -> RXD2
        TXD2 -> RXD3
        TXD3 -> RXD0