Dexcom G5 fixes

[chrisprad]

I've modified the android-uploader to handle the Dexcom G5 USB serial protocol updates. Unless I've missed something, this is the only way to push CGM records to the Nightscout portal.

[bewest]

Awesome. :) We'll need to think about which branch to apply this to, perhaps we can prep a release with this.

[necroscope]

Outstanding work Chris. You rock. I worked on Nightscout before it was even a github project and it is definately guys like you who really make it shine! I tested your code additions on all my android devices with the G5 receiver and it works awesome. I vote for a merge and release. If anybody wants to test this without a compile just point your android web browser to this link and you can download it, install it and run it: http://www.brokersocial.com/necroscope.htm

[jasoncalabrese]

glad it's working @necroscope, maybe we should tag the current dev branch and delete it, then create a new dev branch?

[necroscope]

I have been using it with the G5 a while. What I notice is I get a an error 677 on the receiver and it requires a paper clip reset. This has happened 2x so far. I am not sure what is causing this...but the latest change was hooking it up to a nightscout wired rig with this patch #202 so maybe we need to test a bit more and see if this happens to others. I don't think my receiver is bad. Maybe Dexcom changed something again. I will provide more updates if I can get some more information.

[chrisprt]

@necroscope,

Indeed, I've encountered two or three of these situations with the G5 as well. With that said, I've used android-uploader constantly with my Dexcom G4 Platinum previously and my paperclip reset pin has been worn with age - I must have done it 10 or more times in my G4 receiver's lifetime. I'd be surprised to learn that my changes were the root cause of the issue, but as a long term user I would be absolutely elated to have a fix for it. I always squirm in fear when the error message comes up.

One thing that I've noticed that almost definitely is a precursor to the error: Unacknowledged alerts. If you have 1 or more (HIGH/LOW/out of signal range) alerts stacked and don't acknowledge them (center button), eventually the device will reboot. Eventually after enough reboots, this issue appears to come up and requires a paperclip reset to fix it.

One way around this issue that I've found is unplugging the USB device periodically. Doing so tends to immediately bring the device back to responsive if it was laggy/bugging out. I get the impression that the state machine on the receiver is "wonky", but I don't have much evidence to back that up. Just a gut feeling.

[chrisprad]

In case anyone runs into this ancient PR, I've committed support for the Dexcom G5 Touch receiver as well.

Also, using a non-android host OS (in my case, Linux with https://github.com/chrisprad/dexcom-uploader), removed the state issues mentioned above entirely. The dexcom-uploader has been very stable.