Changing smartphone on Dexcom G6

Until today I was using my wife’s smartphone to control my G6, however today I received a new phone which has BLE 4.2 (my old one, a Sony Xperia Z) did not. I copied the settings from my wife’s phone with the QCode[1], rapidly disabled mine as master (so it was a follower; my wife’s was still set to master obviously) then waited for a connect. [1]This is using xDrip+, not the Dexcom app which never worked for me.

What happened next has been reported elsewhere with no attempt to explain why it happens; no connect. I did however take a careful look at what happens; my new phone temporarily connects to the transmitter, says something like “authenticating” (ha ha, software developers think their users are some kind of all seeing demi-god with instant visual cognition.) Then it stopped.

The error logs show that my new phone is getting authentication failures from the transmitter (it isn’t near enough to my Contour Next BG meter to communicate successfully, but anyway, when it was it was getting packets just fine.)

So at this point I suspect or other of:

  1. The G6 transmitter only supports one ‘master’ and therefore if you damage the master you have to eject the sensor and start a new one with the new master (an operation which, in the US, is as expensive as buying a new smartphone.)
  2. Maybe the transmitter only supports two connections per session (per sensor); so if one of the connected devices fails you simply cannot connect a second. I’ve tinfoiled my Dexcom receiver (I also did “shutdown” but quite frankly I don’t trust the people who write this software.) So I can try in a couple of days time to see if the transmitter resets independently of the sensor, but I don’t have much hope for this.
  3. Major disaster: the transmitter is hardwired to the first two connections it sees, so I have to actually replace the transmitter to replace my cellphone. That would be ridiculous, but then that’s entirely believable.

I’m therefore somewhat interested in whether anyone has managed to connect three devices to a G6 transmitter or whether anyone has managed to replace their cellphone without either junking the sensor or, horrible possibility, junking the massively overpriced transmitter.

John Bowler

Ack! That would be awful. I can’t offer more than some sympathetic support, as I’m using the G5. Hopefully, this isn’t the case and the workaround will be forthcoming and easy!

For xdrip issues, get a Github account and log your issue on that site.

I believe I’ve found out how to get it right - it looks like a misunderstanding on my part of the UI. Since I had started the sensor on my wife’s cell I didn’t start it again on my new phone; I assumed that all the settings would be good. The Contour Next One meter communicates fine with both phones by bluetooth; the settings were copied correctly and in the past I thought I had got xDrip+ to sync without doing the ‘start sensor’. It’s also kind of scary to ‘start’ a sensor that costs hundreds of dollars when it is only 3 days into its 9-10 day life.

Nevertheless I did try a start this morning; I did a complete set up of a G6 on the new phone, including doing the ‘start sensor’ step with the original calibration code. After a few minutes the new phone started working.

The steps I went through are as follows (some of these may be unnecessary):

  1. Install xDrip+ on the new phone and go through all the intro dialog, skip the sensor setup stuff.
  2. On the old phone from xDrip+ use:
    Menu/Settings/Show Settings QR codes (right at the bottom). Chose “Copy All Settings”
  3. On the new phone from xDrip+:
    Menu/Settings/Auto configure (bottom of first page of the settings dialog) and, after oking xDrip+ to use the camera, center the QCode from the oldphone in the display until it gets accepted.
  4. On the old phone stop the phone being the xDrip+ master:
    Menu/Settings/XDrip+ Sync Settings (middle of the last page), uncheck “Be master for followers” if it is checked.
  5. On the new phone use:
    Menu/Start Sensor (the third entry in the menu).
    If it isn’t there, for example if it says “Stop Sensor”, I don’t know what is happening. I think you can get it to reappear by reseting the data source from the button on the home screen: hold down on the xDrip+ icon at the top until the screen washes out and four entries starting with “Source Wizard Button” appear, turn on the first option, go back (to the home screen) and click on the button. You can turn it off afterward, it just wastes space.

Either way at the end of step (4) you will be prompted to select the original calibration code and enter when the sensor was started (you can get that from the old phone). Eventually the sensor will appear on the new phone, if it has sufficiently up-to-date bluetooth.

At this point the new phone is working. You can go back to the old one and change its data source:
Menu/Settings/Hardware Data Source, check “xDrip+Sync Follower”, if you didn’t do (3) above it will tell you it has changed the option to be a follower, not the master, but it’s still set as ‘master’ in the settings so I suggest doing (3) anyway.

Now on the new one do (3) above but turn the ‘master’ option on. They have the same secret key because of the copy in (1) so they should just start talking to each other. You can enter BG readings from either (by default).

Glad u got it sorted out.