I tested three different USB to RS422/485 converters, same model, same revision of pcb
One has no output, one has a fairly high rate of errors and one, the one I was using before , had only the occasional error.
I verified hookup and the only way I get the receive light flashing is with the current hookup ... so verified as correct.
When I looked at the VDR file of the best of these converters, I found that the only character, a comma, hex 2C, is converted to hex 0C. It just drops one bit. Dropping of the comma happens randomly, but no other characters seem to be affected (although this was only verified with a small sample of errors)
The independent GPS puck which, when enabled goes directly to USB without going thru a NMEA 0183 to USB converter, shows no errors.
Based on this, I suspect that either the converters I have are crap or that the NMEA 0183 signal is at a marginal voltage and the converter has issues with that.
In any case, signalK should validate any incoming sentence to make sure the characters in the string are between hex 20 and 7F and any string that contains other characters should be discarded.
I would be interested to hear if anyone else has run into the issue of errors from their NMEA 0183 converter and how this was resolved (keeping in mind that only signalK barfs at these errors and all other consumers of the NMEA data seem to automatically discard the bad data or at least don't crash)
The NMEA 0183 to USB converter is the one that is officially supported, green light flashes strong and clear on all units tested (even the one that gave no output)
One has no output, one has a fairly high rate of errors and one, the one I was using before , had only the occasional error.
I verified hookup and the only way I get the receive light flashing is with the current hookup ... so verified as correct.
When I looked at the VDR file of the best of these converters, I found that the only character, a comma, hex 2C, is converted to hex 0C. It just drops one bit. Dropping of the comma happens randomly, but no other characters seem to be affected (although this was only verified with a small sample of errors)
The independent GPS puck which, when enabled goes directly to USB without going thru a NMEA 0183 to USB converter, shows no errors.
Based on this, I suspect that either the converters I have are crap or that the NMEA 0183 signal is at a marginal voltage and the converter has issues with that.
In any case, signalK should validate any incoming sentence to make sure the characters in the string are between hex 20 and 7F and any string that contains other characters should be discarded.
I would be interested to hear if anyone else has run into the issue of errors from their NMEA 0183 converter and how this was resolved (keeping in mind that only signalK barfs at these errors and all other consumers of the NMEA data seem to automatically discard the bad data or at least don't crash)
The NMEA 0183 to USB converter is the one that is officially supported, green light flashes strong and clear on all units tested (even the one that gave no output)