There was something funny about the pinouts, as I recall (anyone have more details?) but more importantly, when docked in the car, it drops down to 4800 BPS. If you're trying to communicate at 115200 BPS, that's likely your problem.

This number is adjustable with a config.ini modification, but it might be easier just to run your adapter at 4800bps if you can.

Someone else post more info about the pinouts...

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Tony Fabris