From MicronetToNMEA to AvNav on a Raspberry Pi over USB

[nmeyne]

We are using AvNav as a Chartplotter running on a Raspberry Pi (RPi) with GPS and AIS coming over wires from an ICOM AIS device. All is working well. We also have an old TackTick Micronet on the boat which we would like to connect via NMEA0183 to the new chartplotter. I have built a MicronetToNMEA installation on a teensy 4, with CC1101 and a compass. The setup menu seems to compile, start and work normally when accessed from the monitor in the Arduino IDE on my main Linux computer.

When I try to connect with AvNav, it detects and tries to open the USB port for MicronetToNMEA(MTN) ... all good so far, but then I need to get a reliable console connection to do the calibration from the AvNav Rpi installation, so:

1. SSH into the AvNav Rpi
2. Open up a terminal emulator (tio) on the Pi to connect to the USB serial port 'discovered' by AvNav, using what I hoped was pretty standard serial configuration
3. enter '0' and try to operate from the setup / calibration menu options
4. start the conversion and get AvNav to open and send / receive to the USB port

Unfortunately the output at 3 is patchy and slightly scrambled even at 4800 baud. I have tried lots of settings by trial and error, but without success in getting clean comms. It seems to me that perhaps the monitor in the Arduino IDE on my other linux computer works nicely because it is using a special library that provides compatible serial comms objects:

This is not 'standard' serial and will need some code at the AvNav end.. any suggestions / alternative ideas? Otherwise it looks like I am stuck! Grateful for any advice!
Nick

[nmeyne]

Apologies - this is now working fine. I did not realise that I had another process still running that was in contention for the port. I stopped it and the tio console to MicronettoNMEA seems to be working without any obvious data errors. I need to investigate the port speed settings a bit more as well. Thanks for your patience!

[Rodemfr]

Sorry for not answering earlier.
Happy to hear that it is working fine now.
There is something interesting to know in the way MicronetToNMEA (MTN) serial port is working : when you use a Serial-over-USB connection with MTN, the baudrate is in fact not used by the system. The actual baudrate is the one of the USB. It can be more than 400MB/s on a Teensy. So if the Raspberry PI decides to send a big burst of data to MTN, the SW may not be able to cop-up with it.
I don't really know at which level MTN will start loosing data, I never experienced it with my configuration, but it is theoretically possible.