linux-serial-test
Linux Serial Test Application
Compiling
This is a very simple program -- there are several ways to compile it on Linux:
directly using GCC
gcc -o linux-serial-test linux-serial-test.c
Using CMake
cmake ./make
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)
-k, --loopback Use internal hardware loop back
-K, --write-follow Write follows the read count (can be used for multi-serial loopback)
-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. To optionally specify a delay from when the driver is enabled
to start of TX use 'after_delay.before_delay' (-q 1.1)
-Q, --rs485_rts Deassert RTS on send, assert after send. Omitting -Q inverts this logic.
-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)
-I, --rx-timeout Receive timeout
-O, --tx-timeout Transmission timeout
-W, --tx-wait Number of seconds to wait before to transmit (defaults to 0, meaning no wait)
-Z, --error-on-timeout Treat timeouts as errors
-n, --no-icount Do not request driver for counts of input serial line interrupts (TIOCGICOUNT)
-f, --flush-buffers Flush RX and TX buffers before starting
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.
