A lot of questions about Xdrip+

There is a very friendly very helpful xDrip facebook group.
I think that may be more suited to answering your questions than this forum.
They are a private group but pretty open when you request membership.

Some of your questions have been asked previously in that group so, like this forum, I recommend using the Search function before posing them - being a techy group (and your questions are techy), people are more willing to help you if you have helped yourself.

My other tip is to explain your set up when posing your questions. xDrip is global, used for more than Libre and supported on many different phones with their own foibles.

And they refer to PWD rather than "diabetics"

1. will xdrip continue giving readings after the 14 day limit?

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Possibly. I have only done this twice. The first time it lasted for maybe 2 days extra and on the second occasion it stopped about six or seven hours after the expiry time. However I should point out that several people have reported that the libre's results are less accurate coming near the end of the 14 days, hence it is possible that accuracy will be even worse after the 14th day.

2. Will xdrip give readings without the 1 hour delay?

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It asks when you inserted the sensor and does not give you results until the hour is up. I suspect that if you lied, it would give you results immediately. Early results are supposed to erratic, so I haven't tried this.

3. Will xdrip display the actual Glucose indicated by the sensor, even if it is less than 2.2 mmol/L?

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I think the answer is No. (Although the limit might actually be 38 mgValue or 2.1 mmol/L)

4. Can xdrip use NFC or do you have to use a blue tooth bridge?

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Not 100% sure on this. Xdrip can scan using NFC, but when you start XDrip you need to specify your Hardware type and this would not have an option to use NFC alone. (That is because XDrip is supposed to be for continuous monitoring and that is not possible with NFC). Hence I don't know if it is possible to get past this setup without some other hardware. (I have a MiaoMiao)

5. Can you see the raw data which the sensor outputs over NFC?

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There is a 'View Events log' menu option that shows what I presume is the raw data.

6. Can you export all of this data from the android device to a desktop computer?

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You need to setup a nightscout website (see https://github.com/nightscout/cgm-remote-monitor) and Xdrip uploads the information to that website and you can then download the information from there using their API.

There are a couple of fields that I have never used (including filtered and unfiltered) which I assume are the raw data.

7. What is the correlation algorithm used? I would like to run this over the last months data which is on my computer.
8. What is the algorithm to convert the sensor data into PG readings?

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Pass.
Not sure if it helps, but someone did ask that a similar question here https://github.com/NightscoutFoundation/xDrip/issues/87

Are you uploading your LibreLink app to LibreView? It's free and automatic. There are some pretty good reports too. But in addition ALL your data is kept 'for ever' and can be downloaded to your PC. It contains every sensor reading! A data analyser's dream

Well at the risk of being shot down.

Anywhere < 2.2 is pretty academic isn't it?

The hour startup and 14 day life are just parameters you have to live with. Don't really see a problem once you get in the swing of it.

Discrepancies between blood and interstitial fluid will always be the case. Too great and Abbott will change it, but within tolerance seems pretty practical. Again once you've got a 'system'.

As for using the reader. You can upload to Libreview from the website and same applies as I said above, just not in near real-time.

HTH

mattrix said:

I guess it would be academic if the Libre and my finger-stick meter had closer agreement with each other, but the Libre reads far lower than my meter. I did get a replacement for my first sensor, but the replacement and all subsequent sensors have also read lower. That is not to say my meter is perfect, it wouldn't surprise me if it was reading high, but it is what I have tuned my management to. I haven't worked out how to translate my decisions onto the Libre, yet.
If my PG is lower than 2.2 it would be nice to know how much lower, but the Libre just says "LO", for anything 2.2 or less. I hit "LO" frequently and I am not yet hypo, but would be if my PG drops another 0.5 - 1 mmol/L.

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Hi, Abbott is pretty clear on needing to confirm a hypo with a finger prick test. The sensors are less accurate below 4 and above 10mmol too of course.
The way the sensor works, I wouldn't be surprised if it was unable to detect anything lower than 2.2, as I believe it works by detecting a current across the filament caused by glucose in your interstitial fluid. I hope I'm not remembering this incorrectly, but it explains why dehydration can affect readings, as well as pressure. The higher the glucose levels, the higher the current. But definitely do a back up finger prick test when you're hypoing (under 4mmol) to confirm treatment needed. Hope that helps a little.

I'm still thinking you're trying to sail too close to the limits. If you act a bit higher up, the question should become irrelevant. Assuming the Libre is within tolerance. I have my alarms at 5.0 and 8.0 at the moment. This I figure gives me leeway to eat or inject depending on my knowledge of what I am or have been doing.

It is a work in process though.

HTH

UK T1 said:

Hi, Abbott is pretty clear on needing to confirm a hypo with a finger prick test. The sensors are less accurate below 4 and above 10mmol too of course.

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Just a note that this only applies to the Libre1, which both I and mattrix are using. The Libre2 has improved accuracy particularly in the low glucose range and that there is no need to prick your finger even when glucose is low, falling or rapidly changing.
Although Abbott do say that finger pricks are required if your glucose readings and alarms do not match symptoms or expectation.

Source last page of https://www.freestylelibre.co.uk/co...ng from FSL to FSL2 SELF-FUNDED - DIGITAL.pdf

mattrix said:

What will xdrip show me that the Libre reader/meter won't?

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Xdrip will show datapoints on the graph, allow sharing of data without extra steps, connectivity with cloud based apps and most importantly allow for calibration.

mattrix said:

1. will xdrip continue giving readings after the 14 day limit?

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Yes it will but not for too long so ypu may be able to get 15 or 16 days out of each sensor at max. Once past 14 days you would be better off calibrating frequently with finger pricks.

mattrix said:

2. Will xdrip give readings without the 1 hour delay?

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No, xdrip will only start obtaining data once the sensor has been activated and if I recollect correctly it kept trying to connect to Libre 1 but did not get any data until sensor completed 1 hour of activation.

mattrix said:

3. Will xdrip (uncalibrated) display the actual Glucose indicated by the sensor, even if it is less than 2.2 mmol/L?
(the reader/meter just displays "LO")

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Yes it will show the numbers.

mattrix said:

Can I use xdrip as a replacement for the Libre reader/meter?
ie no MaioMaio or internet connectivity

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You cannot use xdrip as replacement to libre app as you still need to activate sensor using official app. However, once activated you don't need libre app as even if you do not have miaomiao you could use the scan NFC function in xdrip setting to manually get the readings. Internet is not required for xdrip to function as reader. Internet is required if you want your data synchronised to the cloud.

mattrix said:

4. Can xdrip use NFC or do you have to use a blue tooth bridge?

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Xdrip allows usage of NFC but its experimental feature and does come with a do at your own risk warning; suggesting in rare cases it can render the sensor useless. I have not had that issue but if the warning is there, why tempt fate. If you have no miaomiao and do not want to invest in one, I would say Libre 2 with Diabox is the perfect way to go forward... details for that are on my blog posts.

mattrix said:

5. Can you see the raw data which the sensor outputs over NFC?

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I think you can, although those raw datapoints were of no interest to me so I never bothered.

mattrix said:

6. Can you export all of this data from the android device to a desktop computer?

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Yes you can through a csv export.

mattrix said:

How does xdrip do its magic?

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Xdrip obtains data from the transmitter (miaomiao or bubble) to which it applies the standard algorith of Calibration by default or the one chosen by user in the settings and then shows the interpreted value.

mattrix said:

7. What is the correlation algorithm used? I would like to run this over the last months data which is on my computer.

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The algorithm they use is on their github page but I am not sure if you can apply that retrospectively to existing data without some programming of your own and still it will be quite unreliable data because when we apply calibration points in the app it uses those points to adjust the slope mathematically. I would recommend not to waste your time on calibrating old data which may not even be accurate and will require more time for less value.

mattrix said:

8. What is the algorithm to convert the sensor data into PG readings?

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As above. There are few other algorithms too but most are reverse engineered by techies far more knowledgable than us mere mortals. Again unless you are a technically aware person heavily into programming and are comfortable understanding and modifying existing codebase, I would recommend not to bother applying that algo to older data. If you do want to know more perhaps their github page will be a good place to start.

mattrix said:

Can diabox do NFC more reliably than xdrip?

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I think so... although I must admit I have only ever used diabox with libre 2. Libre 1 anyway required miaomiao and so I was just used to carrying on with xdrip setup.

The band that comes with miaomiao is not very tight and atleast for me it never resulted in a sensor coming off but I appreciate everyone has a unique use-case.

I agree that calibration is the best feature upgrade to libre sensors achievable through xdrip.