NMEA 0183 Data from Lowrance Chartplotter Received as Garbage

[boybert]

Hi all,

I am exploring OpenPlotter with a test system at home.  I've attached my Lowrance Elite-4 HDI chartplotter to an RS-422/485 -> USB adapter using an FTDI chip, following the pinout in the Lowrance manual (for RS-422; RS-232 instructions are also offered).  When connected to my Pi and recognized by OpenPlotter, I don't seem to be able to get any NMEA data coming through in the Kplex diagnostics windows.

When monitored in a serial console, I can only see garbage/gibberish like this transmission:

Code:

[Æ’}Ìù;;;;;;;;;;;;;[ªvVoÔ[◊.ùùùÀ{Vñ6-V÷ÏvmÎ⁄.6Vˆl-ŸŸŸv-üˆ∂V.vmµmvVoÔ[◊µUkù;;;;;;;;;;;;[õ6VoÔ[◊µU+ù˚˚ˆ∂V.vmu-ˆ¨ñ6-V÷ÏvmÎ⁄.6Vˆl-ŸŸŸv-uÌ6ÌvÌ6ÌvÌ÷ˆ∂ˆˆv≠ˆ6-v-µ≠6ïÎ∑q_qq}ßüüüõïëßôèïô£ôïçüßcßüëìïè£ëìóüßQßüßüßçç£üüßïôßeßßßß´ùùÂÎ∑q_qY}ß}ßùßßßßßßßßßßßßßßçç£üüßçç£üüßü£üü´õyÂÎ∑q_qYSßùßùßùßùôèßôïßõõõß´óìÂÎ.

I have matched the baud rate at 4800, but have also tried several other pairs as I'm able to change the baud rate in the chartplotter.

Could anyone suggest what might be the problem?  Am I using the wrong kind of adapter, for instance?  I don't seem to be able to tease any useful data out of the connection, and I'm pretty confident that I've wired correctly.

Here are the components:
Raspberry Pi 3 Model B
OpenPlotter 1.2.0 Alpha
DSD TECH USB to RS485 RS422 Converter with FTDI FT232 Chip: http://a.co/d/2woKtBi
Lowrance Elite-4 HDI

Thanks for any suggestions!