6 ms·

Electronics Teardown: Stelo Continuous Glucose Monitor (2024)

97 points by walterbell 2y ago

Trasmatta 2y ago
> Imagine a permanent CGM, powered simply by going outside in the sun for 15 minutes a day. What a life! Type 1 diabetic here: one of the reasons for changing the insertion site is because of the risk of infection / rejection. It's not just about the power requirements. As an alternative, Eversense is a long term CGM inserted by a healthcare provider that's supposed to last a year. I've heard mixed reviews. Speaking of mixed reviews, I have mixed feelings about non diabetics using CGMs. But if it lowers the price for all of us, then I'm on board.
- xnx 2y ago
  > I have mixed feelings about non diabetics using CGMs What downsides do you see?
  - Trasmatta 2y ago
    There are no downsides, really. It's mostly an emotional thing that comes from dealing with an awful chronic disease. So I mostly keep it to myself. e.g., I feel sad when a non diabetic uses a CGM and says something like "omg I had a milkshake and my blood sugar spiked all the way to 120!". There's nothing wrong with them saying that, of course. It's just challenging to hear when you have a body that can't produce insulin at all.
    - mynegation 2y ago
      I understand your feelings. One upside that I see from more people using it for non-medical purposes, is more data. That could potentially lead to new research and insights about diabetes, nutrition, and health in general.
      - Trasmatta 2y ago
        Yes definitely! Overall I see it as a win, which is why I don't say these things to non diabetics using CGMs that I meet IRL. I think it's a win for diabetics and non diabetics, and it's more about my internal grief of living with an incurable chronic illness (that I can take to my therapy session).
    - ineedasername 2y ago
      I used one recently on suspicion of a problem based on an odd but not typically related test result. Fasting glucose and a1c on bloodwork were fine. The CGM however showed blood sugar ping ponging from 120 to 200 all day, barely getting back to 120 by dinner after a lunch spike, and lows overnight, even worse < 70 when the dawn phenomena should be pumping it higher. The CGM has saved an unknown period of time by providing detailed metabolic data that traditional tests couldn’t
      - rzmmm 2y ago
        This sounds like a faulty CGM which is very common. With these values normal A1C, <5.7% doesn't sound plausible.
        ineedasername 2y ago
        Periodic finger prick tests during peaks and valleys confirmed it. A1C is a long term average and will not pick up issues that have developed in the past 4-6 weeks.
  - Reventlov 2y ago
    I've seen stock-outs on free freestyles, following “influencer” videos on tiktok. That's a problem.
    - blagie 2y ago
      It's a problem that solves itself: - If more people buy something, in the short term, you have shortages. - In the long term, you have better economies of scale and prices go down. These things should be available for maybe $15 at most, generically, off-brand. Personally, I think this is the kind of exercise most people should go through perhaps annually.
    - scheme271 2y ago
      The freestyle shortages were due to issues with production of the libre 3 and a transition from libre 3 to libre 3+. Abbott really kind of screwed things up with the transition (coupled with a recall on some of the sensors)
- geor9e 2y ago
  Yeah, battery life was never a problem. The Dexcom G4 battery lasted like seven months. I've heard of some people claim they can keep a sensor going a few months, by restarting the transmitter, but they're definitely outliers. For most people biofilm builds up and the sensor data gets really noisy. Massaging the flesh around the sensor can help extend it. I typically go ~20 days per sensor.
  - DaFuk 2y ago
    No restarts required if you use the Anubis transmitter. The battery is replaceable too. I get 14 days out of most but by day 10 the readings are lower than actual, I have to finger stick test and calibrate.
walterbell 2y ago
Will we see open-source software that can interact with these sensors? https://sequenex.com/the-otc-cgm-market-comparing-stelo-lingo-libre-rio/ https://sequenex.com/the-otc-cgm-market-comparing-stelo-ling... > Stelo, created by Dexcom, was the first of these sensors to receive OTC approval from the FDA. This small, completely disposable device uses the same hardware as the Dexcom G7. The main difference between it and the prescription-only device is the software that pairs with it. While the sensor has the same capabilities as the one marketed for people on insulin therapy, the OTC software restricts much of this functionality. > Lingo.. uses the same hardware and housing as the [prescription-only] Freestyle Libre 3. Like Stelo, the software system is where the real differences exist... Abbott’s second OTC CGM is Libre Rio. This sensor looks identical to the Lingo and Freestyle Libre 3. The main difference is in the marketing
- Trasmatta 2y ago
  I believe xDrip works with it. I use it for my G6. The app is amazing, SO much better than the official Dexcom app.
  - guiambros 2y ago
    My understanding is that the Stelo doesn't offer an API, like the Dexcom G6/7 does. That is really unfortunate, because the default Dexcom apps are terrible (the Stelo app is slightly better / more modern, but has all the limitations of the Dexcom app, plus no calibration).
    - geor9e 2y ago
      So xDrip was created to completely skip the Dexcom APIs. With G4 we used a wixel microcontroller, to pass the proprietary radio signal to bluetooth. We'd carry it in our pockets in a tiktac case with a lipo. A graph of our blood sugar would show on our Pebble smartwatches at the time. Once Dexcom built Bluetooth into their transmitters, xDrip was then able to directly pair. There's a lot of smart people on the project, reverse engineering all the Dexcom protocols, and even some other brands of CGM. It does work with Stelo too. xDrip can then sync the data it collects to various APIs/websites. I've been a dexcom user since G4 and never once signed up for a Dexcom account or installed a Dexcom app - the open source stuff was always so much better.
aurizon 2y ago
Is depletion of the glucose oxidase reagent the limiting factor, versus the ~~17 week estimated battery life? One would expect an item with a 17 week battery that also has the glucose oxidase reagent electrode that also lasts ~~17 weeks to have a higher service life - since it does not, I expect the electrode is the limiter and it might have perhaps 30 days? Of course, it has a clock and a limited life to guarantee correct service beyond the 15 day clockout. It will take a better hacker than me to amend the software to explore these electrode limits in a safe manner. One would expect a foreign body might face attack by the body that inexorably acts to cover/passivate this foreign body.
- walterbell 2y ago
  Some discussion in this 2018 article, https://hackaday.com/2018/12/03/why-is-continuous-glucose-monitoring-so-hard/ https://hackaday.com/2018/12/03/why-is-continuous-glucose-mo... https://idoroseman.com/freestyle-libre-blood-glucose-monitoring-system-teardown/ https://idoroseman.com/freestyle-libre-blood-glucose-monitor... > The sensor life is limited by the amount of chemical coating on the probe and the amount of glucose in the interstitial fluid. It could last longer for a person with low and steady BG than for one with chronically high, so the sensor life is a conservative compromise between battery size, Bluetooth wake cycles, and probe life. If the probe had a larger supply of reactant or its dispersal rate could be slowed, the sensor life could be extended to the battery capacity or the max that the FDA would permit.
  - aurizon 2y ago
    Thanks for that +
- geor9e 2y ago
  On the G4 through G6 generation of Dexcom sensor, there is a trick to restart the timer. So I regularly get about 20 days per sensor. The limiting factor is really just the sticker peeling off. So you have to put some kinesiology tape over the whole thing to keep it on. The other limiting factor is the noise in the data gets bad. By massaging the flesh around the sensor, I can make the noise go away. so i don't think the reactant is running out, i think it's biofilm building up so it can't interact with the interstitial fluid as directly.
geor9e 2y ago
If you like this, you might like the Omnipod teardown as well. It's what pairs with continuous glucose monitors. It's an entire insulin pump that you throw away every three days, so the engineering to make the parts that cheap is pretty amazing. They don't waste money on any motors. they just ratchet a worm gear with something called muscle wire. It's a nicanol alloy that shrinks when current heats it. You hear a click click click as it injects a 20th of a unit of insulin at a time. https://www.youtube.com/watch?v=e2MQUUkubgs https://www.youtube.com/watch?v=e2MQUUkubgs
- quanto 2y ago
  SMA wires are not particular cheap. Rather, due to mass production of cellphones, small "pager" motors are incredibly cheap (tens of cents). From the video, it seems that the SMA wires used for precise control & counting of the gear teeth. Thanks for the awesome video.
  - geor9e 2y ago
    It's pretty cheap https://www.sparkfun.com/muscle-wire-0-005-diameter-1-foot.html https://www.sparkfun.com/muscle-wire-0-005-diameter-1-foot.h... It's not the wire that's precise here - it just provides enough force to get a the stamped metal piece over the tooth of the plastic gear, then it slams into a hard stop, then the button batteries dump current into the other wire, which pulls it the other way, pushing the gear one tooth width, and slamming into the other hard stop. Each back and forth ratchet of the tooth turns the worm gear on the plunger the precise 0.05 units. Another cool part of these is the initial insertion - there's a huge torsion spring that stabs a hollow needle into the skin then fully retracts it, leaving the rubber tube. Then there's a little corner of the PCB with a cutout and power trace, you can stab with a paper clip to disable the pod in an emergency. Then there's this membrane that equalizes the air pressure in the pod if you're flying with it. It lets air through but not water. So you can dive in a lake with it too. I love clipping these things open and just marveling at the clever engineering for cheap mass production of such a sophistocated device.
    - quanto 2y ago
shannietron 2y ago
The biggest reason for sensor life is likely due to the sensor (needle) being attacked by immune cells, inflammation or fibrotic scarring. This type of foreign body reaction causes the amount of glucose available to the sensor to drop and reach a point where it just isn't accurate/sufficient anymore This likely why the sensor life is advertised as ~12-15 days: "*Sensor Survival Clarifying Statement: A study was conducted to assess the sensor life where 77.9% of sensors lasted the full 15 days. In other words, when using the product per the package labeling, approximately 20% of sensors may not last for the full 15 days, 10% of these sensors may last less than 12 days." https://www.stelo.com/faqs/using-stelo/how-long-can-i-wear-my-stelo-glucose-biosensor https://www.stelo.com/faqs/using-stelo/how-long-can-i-wear-m...
quanto 2y ago
The 15-day limit is due to the enzyme degradation on the electrode. > While GOx maintains this level of activity in vitro, its stability in vivo is of the order of 10–14 days, necessitating novel immobilization and enzyme modification strategies to extend the functional lifetime of these oxygen-sensitive sensors. https://pmc.ncbi.nlm.nih.gov/articles/PMC3879770/ https://pmc.ncbi.nlm.nih.gov/articles/PMC3879770/ Coincidentally, when I was doing this field of research, I wanted a hardware/software design that could algorithmically compensate for the sensor degradation. I even wanted to mathematically model the electrochemistry to find a clean solution. My electrode was nanoporous platinum, which then was considered more advanced/fashionable/versatile than glucose oxidase coating. In the end, I decided on reading off some cached table, not unlike a consumer electronics estimating remaining battery life. On a separate note, you can design a fuel cell out of blood glucose. So, your body glucose generates electricity to fuel your electronics. The amount of electricity generated is not too off the target power for ultra-efficient circuits, and we even conducted in-vitro experiments as a proof of concept. All of this was 20 years ago. I am glad that there are commercial solutions now but a bit saddened that the field hasn't progressed as fast as other areas of technology.
- MengerSponge 2y ago
  You know better than almost anybody just how hard it is to insert sensors in the body. Optical techniques let you bypass that degradation, and a company actually shipped a portable raman-based glucometer something like a decade ago. Its battery life wasn't good enough, but making a wearable, miniaturized Raman spectrometer was crazy impressive.
  - walterbell 2y ago
    Recent discussion on optical glucose sensors, https://news.ycombinator.com/item?id=43124436 https://news.ycombinator.com/item?id=43124436
    - MengerSponge 2y ago
      Neat. Too bad nobody remembers C8 Medisensors! They went under more than a decade ago, and it's too bad that they didn't leave a lasting cultural or digital footprint. They did ship a raman-based CGM: https://www.diabetesincontrol.com/c8-medisensors/ https://www.diabetesincontrol.com/c8-medisensors/
londons_explore 2y ago
Why is this thing sending 50 bluetooth packets? Wouldn't 1 per 5 minutes suffice? Just a couple of bytes should be fine for the reading. What other data could possibly be needed? To me this smells of it sending a huge json payload with software version numbers and other unnecessary junk simply because the interface between the hardware and app wasn't designed with power efficiency in mind.
- huslage 2y ago
  The sensor likely needs to send all of this info for compliance reasons. Each measurement needs to be tied to the sensor directly I think.
tracker1 2y ago
Between insurance since I couldn't afford the Cobra costs when my last job ended. I've been using these for the past month and they work okay. The only down side is the software states it's not for t2d on insulin or 5qd for that matter. It only shows input from 70-240, outside that range all you know is it's above or below. So it's hard to tell how much correction you need at times. It really sucks how much medications and cgm cost over the counter.
- huslage 2y ago
  The sensor is the same. I wonder if xDrip can read a wider range?
wonder_er 2y ago
I wrote a thing a while ago about my experience with continuous glucose monitors. This post about the Stelo is fascinating. https://josh.works/cgm https://josh.works/cgm
afandian 2y ago
Don’t miss Mike Harrison / “Mike’s Electric Stuff” on YouTube. Here’s his teardown of an insulin pump that has many similarities. https://m.youtube.com/watch?v=e2MQUUkubgs https://m.youtube.com/watch?v=e2MQUUkubgs

97 points by walterbell 2y ago

> Imagine a permanent CGM, powered simply by going outside in the sun for 15 minutes a day. What a life! Type 1 diabetic here: one of the reasons for changing the insertion site is because of the risk of infection / rejection. It's not just about the power requirements. As an alternative, Eversense is a long term CGM inserted by a healthcare provider that's supposed to last a year. I've heard mixed reviews. Speaking of mixed reviews, I have mixed feelings about non diabetics using CGMs. But if it lowers the price for all of us, then I'm on board.

xnx 2y ago
> I have mixed feelings about non diabetics using CGMs What downsides do you see?
- Trasmatta 2y ago
  There are no downsides, really. It's mostly an emotional thing that comes from dealing with an awful chronic disease. So I mostly keep it to myself. e.g., I feel sad when a non diabetic uses a CGM and says something like "omg I had a milkshake and my blood sugar spiked all the way to 120!". There's nothing wrong with them saying that, of course. It's just challenging to hear when you have a body that can't produce insulin at all.
  - mynegation 2y ago
    I understand your feelings. One upside that I see from more people using it for non-medical purposes, is more data. That could potentially lead to new research and insights about diabetes, nutrition, and health in general.
    - Trasmatta 2y ago
      Yes definitely! Overall I see it as a win, which is why I don't say these things to non diabetics using CGMs that I meet IRL. I think it's a win for diabetics and non diabetics, and it's more about my internal grief of living with an incurable chronic illness (that I can take to my therapy session).
  - ineedasername 2y ago
    I used one recently on suspicion of a problem based on an odd but not typically related test result. Fasting glucose and a1c on bloodwork were fine. The CGM however showed blood sugar ping ponging from 120 to 200 all day, barely getting back to 120 by dinner after a lunch spike, and lows overnight, even worse < 70 when the dawn phenomena should be pumping it higher. The CGM has saved an unknown period of time by providing detailed metabolic data that traditional tests couldn’t
    - rzmmm 2y ago
      This sounds like a faulty CGM which is very common. With these values normal A1C, <5.7% doesn't sound plausible.
      - ineedasername 2y ago
        Periodic finger prick tests during peaks and valleys confirmed it. A1C is a long term average and will not pick up issues that have developed in the past 4-6 weeks.
- Reventlov 2y ago
  I've seen stock-outs on free freestyles, following “influencer” videos on tiktok. That's a problem.
  - blagie 2y ago
    It's a problem that solves itself: - If more people buy something, in the short term, you have shortages. - In the long term, you have better economies of scale and prices go down. These things should be available for maybe $15 at most, generically, off-brand. Personally, I think this is the kind of exercise most people should go through perhaps annually.
  - scheme271 2y ago
    The freestyle shortages were due to issues with production of the libre 3 and a transition from libre 3 to libre 3+. Abbott really kind of screwed things up with the transition (coupled with a recall on some of the sensors)
geor9e 2y ago
Yeah, battery life was never a problem. The Dexcom G4 battery lasted like seven months. I've heard of some people claim they can keep a sensor going a few months, by restarting the transmitter, but they're definitely outliers. For most people biofilm builds up and the sensor data gets really noisy. Massaging the flesh around the sensor can help extend it. I typically go ~20 days per sensor.
- DaFuk 2y ago
  No restarts required if you use the Anubis transmitter. The battery is replaceable too. I get 14 days out of most but by day 10 the readings are lower than actual, I have to finger stick test and calibrate.

walterbell 2y ago

Will we see open-source software that can interact with these sensors? https://sequenex.com/the-otc-cgm-market-comparing-stelo-lingo-libre-rio/ https://sequenex.com/the-otc-cgm-market-comparing-stelo-ling... > Stelo, created by Dexcom, was the first of these sensors to receive OTC approval from the FDA. This small, completely disposable device uses the same hardware as the Dexcom G7. The main difference between it and the prescription-only device is the software that pairs with it. While the sensor has the same capabilities as the one marketed for people on insulin therapy, the OTC software restricts much of this functionality. > Lingo.. uses the same hardware and housing as the [prescription-only] Freestyle Libre 3. Like Stelo, the software system is where the real differences exist... Abbott’s second OTC CGM is Libre Rio. This sensor looks identical to the Lingo and Freestyle Libre 3. The main difference is in the marketing

Trasmatta 2y ago
I believe xDrip works with it. I use it for my G6. The app is amazing, SO much better than the official Dexcom app.
- guiambros 2y ago
  My understanding is that the Stelo doesn't offer an API, like the Dexcom G6/7 does. That is really unfortunate, because the default Dexcom apps are terrible (the Stelo app is slightly better / more modern, but has all the limitations of the Dexcom app, plus no calibration).
  - geor9e 2y ago
    So xDrip was created to completely skip the Dexcom APIs. With G4 we used a wixel microcontroller, to pass the proprietary radio signal to bluetooth. We'd carry it in our pockets in a tiktac case with a lipo. A graph of our blood sugar would show on our Pebble smartwatches at the time. Once Dexcom built Bluetooth into their transmitters, xDrip was then able to directly pair. There's a lot of smart people on the project, reverse engineering all the Dexcom protocols, and even some other brands of CGM. It does work with Stelo too. xDrip can then sync the data it collects to various APIs/websites. I've been a dexcom user since G4 and never once signed up for a Dexcom account or installed a Dexcom app - the open source stuff was always so much better.

aurizon 2y ago

Is depletion of the glucose oxidase reagent the limiting factor, versus the ~~17 week estimated battery life? One would expect an item with a 17 week battery that also has the glucose oxidase reagent electrode that also lasts ~~17 weeks to have a higher service life - since it does not, I expect the electrode is the limiter and it might have perhaps 30 days? Of course, it has a clock and a limited life to guarantee correct service beyond the 15 day clockout. It will take a better hacker than me to amend the software to explore these electrode limits in a safe manner. One would expect a foreign body might face attack by the body that inexorably acts to cover/passivate this foreign body.

walterbell 2y ago
Some discussion in this 2018 article, https://hackaday.com/2018/12/03/why-is-continuous-glucose-monitoring-so-hard/ https://hackaday.com/2018/12/03/why-is-continuous-glucose-mo... https://idoroseman.com/freestyle-libre-blood-glucose-monitoring-system-teardown/ https://idoroseman.com/freestyle-libre-blood-glucose-monitor... > The sensor life is limited by the amount of chemical coating on the probe and the amount of glucose in the interstitial fluid. It could last longer for a person with low and steady BG than for one with chronically high, so the sensor life is a conservative compromise between battery size, Bluetooth wake cycles, and probe life. If the probe had a larger supply of reactant or its dispersal rate could be slowed, the sensor life could be extended to the battery capacity or the max that the FDA would permit.
- aurizon 2y ago
  Thanks for that +
geor9e 2y ago
On the G4 through G6 generation of Dexcom sensor, there is a trick to restart the timer. So I regularly get about 20 days per sensor. The limiting factor is really just the sticker peeling off. So you have to put some kinesiology tape over the whole thing to keep it on. The other limiting factor is the noise in the data gets bad. By massaging the flesh around the sensor, I can make the noise go away. so i don't think the reactant is running out, i think it's biofilm building up so it can't interact with the interstitial fluid as directly.

geor9e 2y ago

If you like this, you might like the Omnipod teardown as well. It's what pairs with continuous glucose monitors. It's an entire insulin pump that you throw away every three days, so the engineering to make the parts that cheap is pretty amazing. They don't waste money on any motors. they just ratchet a worm gear with something called muscle wire. It's a nicanol alloy that shrinks when current heats it. You hear a click click click as it injects a 20th of a unit of insulin at a time. https://www.youtube.com/watch?v=e2MQUUkubgs https://www.youtube.com/watch?v=e2MQUUkubgs

quanto 2y ago
SMA wires are not particular cheap. Rather, due to mass production of cellphones, small "pager" motors are incredibly cheap (tens of cents). From the video, it seems that the SMA wires used for precise control & counting of the gear teeth. Thanks for the awesome video.
- geor9e 2y ago
  It's pretty cheap https://www.sparkfun.com/muscle-wire-0-005-diameter-1-foot.html https://www.sparkfun.com/muscle-wire-0-005-diameter-1-foot.h... It's not the wire that's precise here - it just provides enough force to get a the stamped metal piece over the tooth of the plastic gear, then it slams into a hard stop, then the button batteries dump current into the other wire, which pulls it the other way, pushing the gear one tooth width, and slamming into the other hard stop. Each back and forth ratchet of the tooth turns the worm gear on the plunger the precise 0.05 units. Another cool part of these is the initial insertion - there's a huge torsion spring that stabs a hollow needle into the skin then fully retracts it, leaving the rubber tube. Then there's a little corner of the PCB with a cutout and power trace, you can stab with a paper clip to disable the pod in an emergency. Then there's this membrane that equalizes the air pressure in the pod if you're flying with it. It lets air through but not water. So you can dive in a lake with it too. I love clipping these things open and just marveling at the clever engineering for cheap mass production of such a sophistocated device.
  - quanto 2y ago

shannietron 2y ago

The biggest reason for sensor life is likely due to the sensor (needle) being attacked by immune cells, inflammation or fibrotic scarring. This type of foreign body reaction causes the amount of glucose available to the sensor to drop and reach a point where it just isn't accurate/sufficient anymore This likely why the sensor life is advertised as ~12-15 days: "*Sensor Survival Clarifying Statement: A study was conducted to assess the sensor life where 77.9% of sensors lasted the full 15 days. In other words, when using the product per the package labeling, approximately 20% of sensors may not last for the full 15 days, 10% of these sensors may last less than 12 days." https://www.stelo.com/faqs/using-stelo/how-long-can-i-wear-my-stelo-glucose-biosensor https://www.stelo.com/faqs/using-stelo/how-long-can-i-wear-m...

quanto 2y ago

The 15-day limit is due to the enzyme degradation on the electrode. > While GOx maintains this level of activity in vitro, its stability in vivo is of the order of 10–14 days, necessitating novel immobilization and enzyme modification strategies to extend the functional lifetime of these oxygen-sensitive sensors. https://pmc.ncbi.nlm.nih.gov/articles/PMC3879770/ https://pmc.ncbi.nlm.nih.gov/articles/PMC3879770/ Coincidentally, when I was doing this field of research, I wanted a hardware/software design that could algorithmically compensate for the sensor degradation. I even wanted to mathematically model the electrochemistry to find a clean solution. My electrode was nanoporous platinum, which then was considered more advanced/fashionable/versatile than glucose oxidase coating. In the end, I decided on reading off some cached table, not unlike a consumer electronics estimating remaining battery life. On a separate note, you can design a fuel cell out of blood glucose. So, your body glucose generates electricity to fuel your electronics. The amount of electricity generated is not too off the target power for ultra-efficient circuits, and we even conducted in-vitro experiments as a proof of concept. All of this was 20 years ago. I am glad that there are commercial solutions now but a bit saddened that the field hasn't progressed as fast as other areas of technology.

MengerSponge 2y ago
You know better than almost anybody just how hard it is to insert sensors in the body. Optical techniques let you bypass that degradation, and a company actually shipped a portable raman-based glucometer something like a decade ago. Its battery life wasn't good enough, but making a wearable, miniaturized Raman spectrometer was crazy impressive.
- walterbell 2y ago
  Recent discussion on optical glucose sensors, https://news.ycombinator.com/item?id=43124436 https://news.ycombinator.com/item?id=43124436
  - MengerSponge 2y ago
    Neat. Too bad nobody remembers C8 Medisensors! They went under more than a decade ago, and it's too bad that they didn't leave a lasting cultural or digital footprint. They did ship a raman-based CGM: https://www.diabetesincontrol.com/c8-medisensors/ https://www.diabetesincontrol.com/c8-medisensors/

londons_explore 2y ago

Why is this thing sending 50 bluetooth packets? Wouldn't 1 per 5 minutes suffice? Just a couple of bytes should be fine for the reading. What other data could possibly be needed? To me this smells of it sending a huge json payload with software version numbers and other unnecessary junk simply because the interface between the hardware and app wasn't designed with power efficiency in mind.

huslage 2y ago
The sensor likely needs to send all of this info for compliance reasons. Each measurement needs to be tied to the sensor directly I think.

tracker1 2y ago

Between insurance since I couldn't afford the Cobra costs when my last job ended. I've been using these for the past month and they work okay. The only down side is the software states it's not for t2d on insulin or 5qd for that matter. It only shows input from 70-240, outside that range all you know is it's above or below. So it's hard to tell how much correction you need at times. It really sucks how much medications and cgm cost over the counter.

huslage 2y ago
The sensor is the same. I wonder if xDrip can read a wider range?

wonder_er 2y ago

I wrote a thing a while ago about my experience with continuous glucose monitors. This post about the Stelo is fascinating. https://josh.works/cgm https://josh.works/cgm

afandian 2y ago

Don’t miss Mike Harrison / “Mike’s Electric Stuff” on YouTube. Here’s his teardown of an insulin pump that has many similarities. https://m.youtube.com/watch?v=e2MQUUkubgs https://m.youtube.com/watch?v=e2MQUUkubgs