(2019-09-13, 06:23 PM)glowntiger Wrote: I do this with a hat...Hello
At the Moment I recheck the NMEA0183 Ports.
I get grey hairs… I have never seen something like this. Normaly nmea uses RS422 standard or asymetric RS232 Standard.
Now I have tested a ST60+ Raymarine. This Display has a NMEA Output ( + /- ) normaly you expect that - is gnd or the B Port of the RS422. No. Raymarine ST60+ switch the ground Pin!! means + is always 12V. gnd is gnd and nothing happens. If you put the resistor (120Ohm) between, gnd is also 12V and on Data Moment switch to gnd. This isnt compatible to any Standard?????
After searching in web I´m not the one who have this problem. Why somebody do such a sh**???
I had to edit my old message, because it was incomplete.
The NMEA output is balanced, i.e. the NMEA negative is not the ST60 negative. In the RS-422 communication, the transmitter operates the logical "1" at a voltage of -2 to -6 Volt. and the logical "0" at the receiver input in the range of +0.2 to +7 Volt. This means that the bit amplitude can be up to 13V.
Using an RS485 should work, as it is compatible with RS422 but not the reverse.
I've seen you try to read the SeaTalk sentences. I'm sure you know Thomas Knauf's work.
He published some simple circuits to adapt the SeaTalk signal to RS422.
This circuit is for unidiractional, e.g. read only.
This other circuit is for bidirectional communication.