Serial2RUDICS

For TWR Slocum gliders which is connected via a serial port, change to connecting via a RUDICS listener on the dockserver

I run this as a service on a Raspberry Pi 3B running Raspberry Pi OS (Debian Trixie) for multiple serial ports. See USBToRUDICS@.service for the service template and install.py for automated installation.

We connect pocket simulators, shoebox simulators, and Slocum gliders to the serial ports.

All the output of the simulators is logged.

Initially all output is sent to the dockserver via a RUDICS style connection. The RUDICS connection is dropped after the first dive. Then reestablished upon surfacing. The pocket/shoebox/glider is now only connected while on the surface, similar to a real glider.

Dependencies

• Python 3.11+ (Debian Bookworm ships 3.11; Trixie ships 3.13). CI tests 3.11, 3.12, and 3.13.
• pyserial (pip install pyserial or pip install -r requirements.txt)

Installation

The service defaults to running as the current user with logs written to ~/logs/. Run install.py as your normal user (not via sudo) — it invokes sudo internally for the privileged steps. Running the script itself under sudo would cause the service to run as root with logs in /root/logs/.

1. Add your user to the dialout group (for serial port access):

   sudo usermod -aG dialout $USER
   

2. Install the systemd service template and create the log directory:

   python3 install.py --hostname <dockserver> --port 6565
   

3. Install the udev rule to auto-start on USB-serial plug-in:

   sudo cp 99-ttyusb.rules /etc/udev/rules.d/
   sudo udevadm control --reload
   

Usage

serial2RUDICS.py --host=localhost --port=6565 --serial=/dev/ttyUSB0

To see all the command line options use:

serial2RUDICS.py --help

Operation

Each USB serial device gets its own systemd template instance (e.g. USBToRUDICS@ttyUSB0.service). The udev rule starts/stops them as USB-serial devices are plugged in.

Viewing logs

journalctl -u USBToRUDICS@ttyUSB0.service -f       # live log via syslog
tail -f ~/logs/ttyUSB0.log                         # per-port rotating log
sudo systemctl status 'USBToRUDICS@ttyUSB*'        # all instances

Notable flags

Flag	Default	Purpose
--host, --port	— / 6565	Dockserver RUDICS endpoint
--serial	—	Serial device, e.g. /dev/ttyUSB0
--baudrate	115200	Serial baudrate
--idleTimeout	3600	Drop RUDICS after this many idle seconds
--rudicsBaudrate	(unset)	Optional outbound rate limit toward RUDICS
--rudicsMaxOpenTime	86400	Force a reconnect after this many seconds
--triggerOn, --triggerOff	(defaults)	Regex patterns over serial output that open/close the RUDICS session
--maxBuffer	10485760	Bytes buffered while waiting for RUDICS; lower for tight-RAM hosts
--binary	(unset)	Dump every chunk in both directions to this file (heavy SD I/O)
--disconnected	False	Start with RUDICS disconnected, wait for triggerOn

Trigger / suppression behavior

Default triggers open RUDICS on surface_<n>: ... Picking iridium or freewave or abort_the_mission, and close it on surface_<n>: ... Waiting for final gps fix. Custom patterns are appendable via repeated --triggerOn/--triggerOff.

Trigger matching is suppressed during file transfers to avoid spurious closes:

• Lines that contain non-text bytes (zmodem framing)
• After a type or cat command at a GliderDos prompt, until LOG FILE CLOSED or the next GliderDos prompt
• Within 30 seconds of any binary data on the wire (active zmodem session)

Notes

This is a Python 3 program. It has been tested on Raspberry Pi OS (Debian Trixie) running Python 3.13, and CI runs the test suite on Python 3.11, 3.12, and 3.13.

The only non-standard Python module you might have to install is pyserial.