Autohelm type 100 autopilot

[Tacmed]

Has anyone connected to the NMEA output on these?
I have been using openplotter for months and know my way arround the system well.
The guy on the yacht next door(we are liveaboards) and liked how i had my system outputting to my EDO intruments on my android tablets and phone.

I connected the official USB to RS422 device to his NMEA output at 4800 baud. All i got was the odd part sentances with no full strings. The LED flashes to indicate date is comming in.
I have tried the wire reverse, common ground...usual stuff to no avail.

Has anyone tried to connect to one of these?

They seem to be common units. All instruments connect in, one seatalk output for displays, a NMEA in for GPS and an NMEA output D+ and D- type NMEA.
The autohelm documentation says 4800 baud and a list of sentances it will spit out.

I couldnt remember the linux terminal command to show raw data on the linux terminal.

I did check the kplex config file and all seemed okay.

Cheers.

[Tacmed]

Follow up to save others time in connecting.
An RS422 module will not work. An RS232 to USB on recieve will match the date close enough to get the 4800 baud data.
Open plotter will display the sentances, however, there are no checksums at the ends, which means the data can not be recieved by most wifi digital instruments.
Autohelm units dont seem to send out full nmea sentances.

Does anyone know of any conversion software that will run on a Pi or arduino?

As for the electronics in the Autohelm 100, the circuit board looks like there is a switching transistor sending pulses out, which means it is designed to turn on and off an optoisolator. Maybe the reverse polarity of the mark/space logic level could be a problem for some USB serial converters. This would explain why some arduino nmea software has the option of inverting the serial logic levels.

Ie, is a positive on the output would turn on an opto, this would give you a logic low on the listener input. This would corrupt some FIFO serial buffers.

[SYWindveer]

AH 100 is an older unit, so the interface could well be RS232 instead of RS 422.
OpenPlotter uses Kplex as a multiplexer.
The Kplex documentation suggests Kplex can generate checksums;

"checksum": May be "yes" to enable checksumming of incoming sentences on an interface or "no" to disable it. This option overrides the global checksum option.

Minicom is a nice terminal emulator that you can use to monitor serial devices

sudo apt-get install minicom

If the logic level is inverted you should see garbled text.