G7 Overlap Query

[twaymouth]

Hi, I have a query relating to xDrip and overlapping G7 sensors.

For some background I used G6 in the past and am currently trialing G7, with the G6 I ran 2 variants of xDrip on my phone, 1 variant that managed my active sensor, alarms, sent data to AAPS etc and a 2nd variant with all alarms etc disabled that I would use to warm up a new sensor for 12 – 24 hours.

Once I was happy with how the new sensor was performing, I would disable collection in the 2nd variant and change the transmitter ID in the 1st variant to take over the session from the 2nd variant.

I attempted this for the first time with a G7 sensor however when it came time to swap the transmitter IDs between variants I could not make the 1st variant connect to the sensor. I disabled collection in the 2nd variant, waited 15 minutes and then put the transmitter ID in the first variant however no matter what I did the 1st variant was not able to get readings from the sensor?

I eventually put the transmitter ID back in the 2nd variant as I needed the data and it started working right away, not sure if this is expected behavior with the G7 or if I have done something wrong or is it not recommended to overlap G7 in this manner?

Seems somewhat similar to #3920

[Navid200]

Fortunately, unlike G6, there is no need to start anything with G7. If you don't start a G6, nothing will work. G7 starts automatically as soon as you insert the sensor.

But, the need remains to establish connectivity to the newly inserted G7 to verify if it is functional or if it is a faulty device as there are times a G7 fails.
Only for this purpose, I use a second device. You can use a second phone or a BlueJay watch.

I suggest that there is no reason to monitor the new sensor until it is good enough. Just let it run until your current sensor expires. After your current sensor expires, you have no choice but to switch to it.

This is what I do:
Every 10 days, I insert a new sensor in the morning. I have been doing this even with G6 because I will have 12 hours to deal with any unexpected issue by the time I want to go to bed at night.
When I insert the new sensor in the morning, I also have an old sensor that still has about 12 hours to go.
At that point, with my main phone connected to my old sensor, I use another device to connect to the new sensor. After the 30-minute warmup is over and I see readings, I stop using the alternative phone because it has done its job, to verify that nothing is wrong with the new sensor.

Throughout the day, I have two sensors on me while I am collecting only from the old one. The new one is there and is working but am not getting any readings from it.

When my old sensor expires at night, I peel it off and move it away, far away, to ensure it will be out of Bluetooth range.
Then, I switch the transmitter ID on my main phone to the pairing code of the new sensor. xDrip then switches to the new sensor and backfills.
Unfortunately, we currently have an issue that causes a backfill overlap. This PR has fixed the issue and I hope that it will be merged so that everyone can benefit from it:
#3872

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I appreciate that needing a second phone is an inconvenience.
xDrip has a limitation in connecting to a G7 if there are two G7 devices side by side both trying to connect (both in rapid reconnect mode).
I am not aware of a way to do this with a single phone.

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I have summarized this here:
https://navid200.github.io/xDrip/docs/Dexcom/SubsequentG7.html

[twaymouth]

Thanks for the comprehensive response, I guess I liked to see the readings from both sensors as with the g6 it would not always be stable and ready to use after 12 hours, because I was using an Anubis transmitter I could wait as long as I needed.

As you noted with the g7 you have no choice but to switch when your active sensor expires so as long as you can confirm the new one starts correctly no additional monitoring is required. I do have an old phone so I'll look at using that to start my new sensor then switch to my main phone once it's time.

Thanks.

[Navid200]

I decided to test using a variant this time with my new sensor and I was able to use one to verify that the new sensor was functional.

The problem I can see many will experience is that they may think they can just switch the ID to switch.
You cannot do that. If you want to switch your main xDrip from the old one to the new one and you just change the pairing code, you will have two sensors on you both trying to connect and xDrip may not be able to connect to the right one.

So, when the time comes that you are happy with the new sensor and you intend to switch to it for sure, the best course of action is to peel off the old one and move it away. You should stop collecting from the new one with the variant or the other phone.
You should then wait 15 minutes.
Then, you can switch the transmitter ID to the pairing code of the new one. If you have moved the old sensor far away, it will not be able to interfere and you will be able to connect to the new one.