I don’t even know how the calibrate process works. @dm61 do you have an understanding of how the xdrip+ calibration works?
One possibility as I see it (thinking on the G5) is that the calibration data points are stored within the Transmitter memory. (We already know it has a decent sized memory to be able to hold 3 hr of backfill so likely it can hold a number of other data elements.) The transmitter perhaps holds the six most recent calibration data points (BG and time) as entered. The transmitter might send an uncalibrated (raw?) data signal every 5 minutes to the Receiving device. As well, queuing/messaging technology could be used to send the calibration data points and 3 hr of backfill only if needed. The 505 algorithm running on either the Dexcom Receiver or the Dexcom G5 Mobile App or the Tandem t:slim X2 might then use a linear least squares regression method to “on the fly” apply the calibration data points to the raw data so as to produce a final BG reading.
Or it could be doing something entirely different.
There is a guy who did this a lot with G4’s and made videos about them on Youtube. I asked him if he’d be posting a G5 video and he indicated this will be coming in the very near future so hopefully something will be published by him soon - if it is, I’ll link it.
His videos are very thorough and awesome videography also, so I really hope he posts them - he doesn’t leave out a single step and each one is fully explained.
I am still puzzled by the calibration questions It seems to me it is very likely to be on the G4 receiver — although the G4 could pass the updated code along to the transmitter in an update process.
it seems like the likely thing, since, when you calibrate on any device, the results are shortly reflected on others. but…
I agree too.
This is new info to me – yes, I also agree that it implies it happens outside the transmitter.
Not really. I’m not using Xdrip+ so I’ve not looked into the code or any other materials or discussions around Xdrip+. If you are into reading Java, here is how calibration is implemented. At a glance, it appears the calculations are done based on raw data coming from the transmitter, and values from the meter, as one would expect. For people interested in Xdrip+ technical details or questions, I’d recommend the Xdrip-plus gitter channel.
Should be an easy experiment to determine if the syncing is occurring on the receiver or not with the G5. Run it with the phone while the receiver is off. Then then turn off phone and the receiver on and see if it picks up the correct data-- if so it must have came from the transmitter
Good point - agreed. I do not have G5, so I am unable to perform the experiment, but I’d be interested to know of the outcome of the experiment.
After looking around some more, I think the most likely scenario is that G5 calibration algorithm still resides on the receiver and on the app, but the calibration parameters are communicated back to the transmitter, which is how all receiving devices are ultimately synced regardless of their on/off state at the time of calibration.
That would be what it would determine… whether the transmitter is a 2- way device or just a “transmitter”
ETA just tried it and even with my phone completely off the transmitter fired up, required no calibration and reflected same level as phone had before I powered it down so I agree that the calibration must be somehow acknowledged by the transmitter itself
Small point, but in your Oct 9 Resources list, the link for Dexcom Clarity is for the US site, which last time I checked used mg/dL only. People in countries using mmol/L (such as ) will want to go to https://clarity.dexcom.eu/ (which allows use of either unit of measurement).
With respect to the question of whether the arithmetic that converts raw sensor data to a BG value happens in the receiver or the transmitter, the answer is that it was in the receiver for the G4, but in the transmitter starting with the G5. The G5 “smart transmitter” was explained (at a high level) by the CEO in a couple quarterly conference calls a while ago (about a year?). The G5 transmitter does it so that it can send consistent BG values to simple display devices (like watches) without requiring that they implement all the logic, and to make it easy for multiple devices to interact with the G5 transmitter without complex protocols to keep track of which receiver/pump/phone is in charge: the transmitter is always in charge.
@bkh - Would you be able to provide a link? I just searched the 2016 and 2017 quarterly earnings calls and couldn’t find it so I must be missing it. I would be interested to read what he said. Thanks.
I think I found the reference to the Dexcom smart transmitter - going back further - in the 2015 Q1 Earnings Call.
However, I don’t see how this makes sense in terms of the xdrip functionality also working? Maybe @docslotnick has some thoughts on how the xdrip could fit into this?
April 29, 2015
Kevin Sayer, CEO, Dexcom
Let’s start with Gen 5. As I stated in my opening remarks, the G5 mobile system was filed with the FDA in February of this year.
The key component of this system is a smart transmitter. The algorithm currently running on the receiver will instead reside in the transmitter. The smart transmitter will directly send a glucose value via Bluetooth low energy to up to two devices. Patients will no longer be required to carry a receiver for connectivity, excuse me – as they do now. The signal will go straight to the smartphone.
The G5 mobile platform will have a significant impact on DexCom as well. The G5 mobile system utilizes our FDA-approved G4 PLATINUM sensor with the improved 505 algorithm so there will be no disruption in sensor operations for this launch.
Currently, we believe that the FDA will require each new patient to purchase a DexCom Receiver, which will more than likely be used as a backup.
It seems to me it is very likely to be on the G4 receiver — although the G4 could pass the updated code along to the transmitter in an update process.
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