NMEA Update

When we got back to Gosport the Raspberry Pi was broken. I've no idea how but it wouldn't boot and the yellow LEDs for the ethernet didn't light. When I got it home I connected it to the TV and it wasn't even trying to boot.

I tried to bypass it so we could at least get depth but it didn't work Some days I'm just not good enough.

I had another Pi - a Pi0W I was trying to get working with some custom hardware but that wasn't ready so I tried combining it with an external USB hub.

These cables have no serial numbers so it isn't possible to determine which is which other than the device ids. Some people claim that it is repeatable but I've seen random ttyUSB allocations.

After some trial and error I got the hardware setup I had originally intended - with four USB to Serial cables on a four port USB hub. I wired the two ct342 cables to the high speed units (chart plotter and AIS) and the two pl203 cables to the low speed Depth unit and VHF.

I finally got the wiring correct so I can see the NMEA sentences produced by the radio. Maybe there will be a way of cancelling DSC alarms from the chart plotter now we have two way communication.

Depth still isn't working reliably. Mostly the depth unit outputs valid sentences with no depth information.

Once it was all wired correctly Kplex kept falling over. It stopped once I turned off the AIS unit. It seems to be an overrun error. It didn't happen with the faster Pi3. But a pi0 should be fast enough for two 38.4 kbit/s and two 4.8 kbit/s links. I'll look into that separately.