NMEA / USB wiring - help welcome ! SOLVED at last !

[Didier B]

Here is a lot of useful information: http://www.actisense.com/wp-content/uplo...-4-1-1.pdf

Thanks a lot, very precious for an NMEA newbie !

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The ST50 is probably so old that it uses NMEA 0183 version 1. This is not RS422 but RS232.
You should try with a USB-RS232 converter (preferebly isolated). Remember to set the baudrate to 4800 baud.

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- on transmiter side is ST50 which have TTL(UART) output
That mean you need  UART to USB converter between this two parts.

I am quite sure that this would destroy the UART to USB converter because it only handles 0 to 3.3 or 5 V, and this output is probably ±12 V.

Maybe, but it will only be 12v not +/-12v.

This converter is very cheap so...
Maybe try to measure ST30 output with oscilloscope to check voltage. If it is 12v, you can use simple voltage divider with two resistor.

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Thanks for yor suggestion of a divider. I guess 12 to 5V ... Any suggestion for the impedance (from ST50 12 V side)  ?