The B600s emits some custom sentences to indicate that there are problems (and also turns on a LED labeled “Err”). Some begin with PAMC, others with AIALR. If I remember the NMEA spec correctly, P* are proprietary, so PAMC is Proprietary AMC (Alltek Marine also call themselves AMEC).
- $PAMC,R,TXT,010,Power anomalies:0.00V*56
- $PAMC,R,TXT,200,GPS antenna is not detected*75
- $AIALR,246060.00,007,A,V,AIS: UTC sync invalid*06
- $AIALR,246060.00,026,A,V,AIS: No sensor position in use*7B
- $AIALR,246060.00,029,A,V,AIS: No valid SOG information*7E
- $AIALR,246060.00,030,A,V,AIS: No valid COG information*66
- $AIALR,246060.00,032,A,V,AIS: Heading lost/invalid*06
- $AIALR,246060.00,001,V,V,AIS: Tx malfunction*4D
- $AIALR,246060.00,002,V,V,AIS: Antenna VSWR exceeds limit*43
- $AIALR,246060.00,003,V,V,AIS: Rx channel 1 malfunction*1B
- $AIALR,246060.00,004,V,V,AIS: Rx channel 2 malfunction*1F
- $AIALR,246060.00,005,V,V,AIS: Rx channel 70 malfunction*2B
- $AIALR,246060.00,006,V,V,AIS: general failure*12
The documentation actually has a listing of all the sentences that the unit will output, which is nice.
What’s interesting is that the Warn light has not come on, despite the VSWR being too high. However, it’s possible there’s some smarts in this thing, and it’s detecting that it’s on USB power and that there’s no VHF actually transmitting (“The orange LED illuminates when antenna VSWR is over 3:1 by VHF transmission at 25W.”).
There’s also a sentence carrying details about the operation voltage, but it didn’t show up when I captured the list above (though there is one about power anomalies). What all of this means though, is that I can build a smart datalogger using an ESP8266 or ESP32, and trigger different alarm tones based on different AIALR and PAMC error messages. Either chip has the ability to poke GPIO pins with power, which can in turn either trigger relays, or I might be able to rig up a buzzer to a set of pins and play custom tones (so different tone sequences for different problems). Plus, I’ve got a 2.4″ display that can be attached to the ESP, so I can display error messages there.