sharkct / linux_serial_demo_userspace

Linux Serial Test Application

linux-serial-test

Linux Serial Test Application

Usage

Usage: linux-serial-test [OPTION]

  -h, --help
  -b, --baud        Baud rate, 115200, etc (115200 is default)
  -p, --port        Port (/dev/ttyS0, etc) (must be specified)
  -d, --divisor     UART Baud rate divisor (can be used to set custom baud rates)
  -R, --rx_dump     Dump Rx data (ascii, raw)
  -T, --detailed_tx Detailed Tx data
  -s, --stats       Dump serial port stats every 5s
  -S, --stop-on-err Stop program if we encounter an error
  -y, --single-byte Send specified byte to the serial port
  -z, --second-byte Send another specified byte to the serial port
  -c, --rts-cts     Enable RTS/CTS flow control
  -B, --2-stop-bit  Use two stop bits per character
  -P, --parity      Use parity bit (odd, even, mark, space)
  -e, --dump-err    Display errors
  -r, --no-rx       Don't receive data (can be used to test flow control)
                    when serial driver buffer is full
  -t, --no-tx       Don't transmit data
  -l, --rx-delay    Delay between reading data (ms) (can be used to test flow control)
  -a, --tx-delay    Delay between writing data (ms)
  -w, --tx-bytes    Number of bytes for each write (default is to repeatedly write 1024 bytes
                    until no more are accepted)
  -q, --rs485       Enable RS485 direction control on port, and set delay
                    from when TX is finished and RS485 driver enable is
                    de-asserted. Delay is specified in bit times.
  -o, --tx-time     Number of seconds to transmit for (defaults to 0, meaning no limit)
  -i, --rx-time     Number of seconds to receive for (defaults to 0, meaning no limit)
  -A, --ascii       Output bytes range from 32 to 126 (default is 0 to 255)

Examples

Stress test a connection

linux-serial-test -s -e -p /dev/ttyO0 -b 3000000

This will send full bandwidth data with a counting pattern on the TX signal. On any data received on RX, the program will look for a counting pattern and report any missing data in the pattern. This test can be done using a loopback cable.

Test flow control

linux-serial-test -s -e -p /dev/ttyO0 -c -l 250

This enables RTS/CTS flow control and sends a counting pattern on the TX signal. Reads are delayed by 250ms between reads, which will cause the buffer to fill up and start using flow control. As before any missing data in the pattern is reported, and if flow control is working correctly there should be none.

This test can be done using a loopback cable, or by running the program on both ends of the connection. For a two-port solution invoke the following command on the receiver side:

linux-serial-test -s -e -p /dev/ttyO1 -t -c -l 250

and on the transmitter side:

linux-serial-test -s -e -p /dev/ttyO0 -r -c

Stress test that can be used in a script

linux-serial-test -s -e -p /dev/ttyO0 -b 115200 -o 5 -i 7

This transmits for five seconds and receives for seven seconds, after which it will exit. The exit code will be zero if the number of received bytes matched the number of transmitted bytes and the received pattern was correct, so this can be used as part of an automated test script.

Output a pattern where you can easily verify baud rate with scope:

linux-serial-test -y 0x55 -z 0x0 -p /dev/ttyO0 -b 3000000

This outputs 10 bits that are easy to measure, and then multiply by 10 in your head to get baud rate.