GPS Mystery Character puzzle, solved via an unusual solution

The ACT lockdown as had it’s up sides, no commuting, limited after school and social activities has meant that I’ve had time to tackle the GPS mystery that’s been bugging me for some time.

A while back I noticed the GPS tagging of the data collected in my Van had stopped. This was somewhat unusual as I hadn’t changed anything (famous last words). When I investigated the issue I found that the feed started to appear corrupted, with the steam of characters displaying symbols and partially decoded (as can be seen below).

I’d invested a number of potential sources of the corruption, tried stopping and restarting, pulled the unit apart to check the wiring and then tried changing the decoding from UTF-8 to an alternate encoding; also reset the WiFi region (random I know but Dr. Google suggested it!!). Finally I thought it could of been the frequency of the data feed, so I also tinkered with the frequency of reading the stream. None of these worked. Interestingly I had tested the FatigueM8 unit on the test-bench and the GPS was working fine. I hadn’t joined the dots at this point.

On returning the unit back into my car, and while awaiting a COVID-19 Test I noticed that the Wifi in my car wasn’t working. Both the FatigueM8 and the 3G/4G Wifi dongal are plugged into a 12v cigarette lighter socket.

I removed the cigarette socket to debug the issue with the wifi, there wasn’t anything noticeability wrong with the wifi dongal, but I did notice the Amperage values on the socket. When setting up the system I had made sure to plug the Compute unit into the 2.1A slot as it needed more power than the wifi dongal. This time when I plugged everything back together I made sure again to put the Compute unit into the 2.1A and the wifi dongal into the 1A slot.

And what do you know, when I started it all up the Orange GPS light flashed on and stayed on (signalling a GPS fix was detected). When I looked at the stream via the logs it was back to being the standard NEMA strings and the GPS was back! Of all the things I thought was causing the “corruption” low power was certainly not high on the list of things to check!!

The GPS hasn’t missed a beat since.

Until next time, stay safe.