ST1 is not working

[atchik]

Hello
I suspect I have damaged st1 input by mixing 12v and ground, which blown fuse on the boat panel (2 amp). Unfortunately multiplexer USB port was connected to raspberry at this time.
Now:
- ST1 devices are still working fine: ST50, wind and deep meters and ST60 in the bus. They all show indication ok.
- ST1 input led does not blink on wifi3nmea
- no St1 signals received by raspberry Pi from USB (p3) wifi3nmea. Changing usb port on rPI does not make any effect.
- changing ST mode on multiplexer does not make any effect
- wifi3nmea NMEA inputs are working fine, receiving signals and sending them to signalk.
- diagnostic mode does not show any signals from ST but NMEA input works ok.
- simulation mode works fine showing everything on opencpn correctly as described
- multimeter shows some voltage between 11 and 12v on ST1 device line and able to detect some AC frequency, I do not have any oscillograph available, but it seem to be ok

Question:
1) is ST1 input only a suspect on the multiplexer, and it should be replaced?
2) any ways to make sure st1 device data line is ok without wifi3nmea?
Thank you

[atchik]

problem solved (just reporting here). ST1 is working.
- root cause - bad cable connection in data line to ST1 input of multiplexer

note: wifi3nmea is very reliable and survived my stupidity of connecting 12v to GND and GND to 12v on ST1 input having USB output connected to computer/raspberry pi. (12v was protected by 2amp fuse)

many thanks to Luis for the excellent design.