minimal Elixir UART port.
{:ok, _} = Uart.start_link(['/dev/pts/3', '9600', '8', 'N', '1'])
:ok = Uart.subscribe()
receive do
{:data, data} -> IO.inspect(data)
{:exit, exit_status} -> IO.inspect(exit_status)
end
...
Uart.write("Hello, world!")
Uart.write(<< 0xDE, 0xAD, 0xBE, 0xEF >>)
plug in cable, then check dmesg
dmesg
[41733.619816] usb 1-8: FTDI USB Serial Device converter now attached to ttyUSB0
# ^^^^^^^
the device is owned by root and group dialout.
sf@grayskull:~$ ls -al /dev/ttyUSB0
crw-rw---- 1 root dialout 188, 0 Jul 10 14:14 /dev/ttyUSB0
# ^^^^^^^ ^^^^^^^
so join the dialout group
sf@grayskull:~$ groups
sf adm cdrom sudo dip plugdev lpadmin lxd sambashare docker
sf@grayskull:~$ sudo usermod -a -G dialout $USER
this seems to have no effect
sf@grayskull:~$ groups
sf adm cdrom sudo dip plugdev lpadmin lxd sambashare docker
you have to login/logout or start a new shell
sf@grayskull:~$ su sf
sf@grayskull:~$ groups
sf adm dialout cdrom sudo dip plugdev lpadmin lxd sambashare docker
# ^^^^^^^
(if still not in group, try a restart)
now you can connect with
{:ok, _} = Uart.start_link(['/dev/ttyUSB0', '19200', '8', 'N', '1'])
# ^^^^^^^
some useful commands for troubleshooting:
dmesg
lsusb
find /sys/bus/usb/devices/usb*/ -name dev
udevadm info -a -p $(udevadm info -q path -n /dev/ttyUSB0)
usb-devices
(byte-stuffed) CEMI-frame
11 AA 00 BC E0 FF FF AA 00 01 01 AA 00 80 00
ESC ^^ ^^ ^^
END ^^
frame = <<0x11, 0xAA, 0x00, 0xBC, 0xE0, 0xFF, 0xFF, 0xAA, 0x00, 0x01, 0x01, 0xAA, 0x00, 0x80, 0x00>>
Uart.write(frame)
- https://www.cmrr.umn.edu/~strupp/serial.html
- https://tldp.org/HOWTO/Serial-Programming-HOWTO/x115.html#AEN125
- https://tldp.org/HOWTO/Serial-HOWTO.html
- https://stackoverflow.com/questions/25996171/linux-blocking-vs-non-blocking-serial-read
sudo apt install socat
sudo apt install minicom
socat -d -d pty,raw,echo=0 pty,raw,echo=0
sf@eternia:~/temp$ socat -d -d pty,raw,echo=0 pty,raw,echo=0
> 2020/11/24 19:38:59 socat[319915] N PTY is /dev/pts/4
> 2020/11/24 19:38:59 socat[319915] N PTY is /dev/pts/5
> 2020/11/24 19:38:59 socat[319915] N starting data transfer loop with FDs [5,5] and [7,7]
minicom -D /dev/pts/4
minicom -D /dev/pts/5
https://serverfault.com/a/443303
mkfifo fifo
cat > fifo & # dummy process to keep the FIFO open
fifo_cat_pid=$!
<program> < fifo
echo "Hello World" > fifo
// cleanup
kill $fifo_cat_pid
rm fifo
- how to handle parity errors? parity needed?