Open Source Medical Devices - I want to change things

Diabetes Technology
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I did a bit of reading, it still looks like you need the Phone/Tablet. This describes it well: http://circles-of-blue.winchcombe.org/index.php/2015/01/11/wearenotwaiting-thanks-to-dexdrip-introduction/

The phones app picks up the reading and relays it to nightscount which puts it on the web, then from there it can go to a watch, website another phone etc. I dont think the smartwatches themselves cannot connect to the DexDrip's bluetooth module. That would be cool, but I don't think that is how it works yet. So for people who do not own a android let a lone a smart watch, they're looking at another couple hundred to get the reading on their wrist. I'm talking less than $50 to get it going, and you wouldn't have to carry around the DexDrip "module" because its in this small device. It needs to be simple, inexpensive, as a "just make things convenient" sort of way. Basically like a heart rate monitor watch.

All of my boards are surface mount, and at least 2 layer. I don't do through hole, mostly 0402 components, so it will be a small form factor. I don't know if touchscreen would be a good idea, very expensive/complex with very little benefit, not easy to do, especially with a micro-controller. It needs to be basic, Use the CC2511 as the microcontroller, and a OLED screen, no daughter board needed. This is the screen I'm thinking but without their large breakout board:

Not much user input is needed, something to change the device ID so it can connect to the transmitter, and maybe something to wake up the watch to get the reading. There are small scroll wheels with a click input that could work well. DexDrips software can then be used directly with very little modification.

I like your forward thinking, but at this point its not going to be a manufactured project.I would love it to be, but financially not feasible right now. I'm thinking just an open source circuit board with a case design that could be ordered on shapeways or 3D printed at home. I can sell the individual boards on www.tindie.com, through my site, or on a personal level like TuD, for those who want them. I can get the boards made in small batch from OSHpark.com for less than $5 a board in sets of 3. As you probably know, getting a batch done in China, while cheap per board still required a large initial cost usually a couple grand. Funding for me is the problem right now. Maybe in the future if there is a high demand we could go that route, but for right now its pretty easy to just order small quantities and build them myself with my toaster reflow oven in as demand is required. Also if someone just wants to go the route and make their own, they can do that as well. I've done a few small run orders, I designed these soil moisture meters for a company and did a batch around 150 boards, has a stainless stencil made, it only took a day or two for assembly. With my PIDDYBOT balancing robot I used a company called OSHstencils.com and they make really precise stencils out of Polyimide for a few bucks and can last for a few hundred boards. Its really amazing what is available to makers now.

I will probably finish up the initial design later today, post up some dimensions, pictures, etc.

42

I haven't made much development on the watch quite yet. Planning out some parts but was a little busy with other things.

I actually received a newer revision PCB of the NIRGM(above image). The glucose monitor that uses NIR light. I added the components to it over the weekend and did a bit of testing but nothing too rigorous. What I changed was the sensitivity to the light response. I will probably have to talk to some of my colleagues about programming it.

If anyone on here wants to build one, who thinks they may want to experiment with programming one(Mario? haha), let me know. I can either provide the files, or working circuitboard, or anything needed to build one. I could build one as well for the cost of parts(can't afford making a bunch to give out right now- if I could I would!), as in gather parts and solder/assemble for you then send it off.

Other than that there is not much of an update unfortunately.

43

If you provide me with a circuit board and a BOM or parts/parts list I can build one up.
What programmer is needed for it? I have access to an arduino and of course my main PC if it has a USB port.
Drop me a message on here and we can work it out. I am glad to help. :)

- Mario

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For those of following this thread, you may be interested in these 2 groups of people who are working on closed-loop pump/cgm systems:

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I received sensors from MarkR, so I could have a look at how they work and so I can test fit my transmitter I designed.

Rather simple in design, some conductive rubber and the wire is fed through it. You can see in the picture below(kind of) how there is 2 layers of the wire and then the insulation - from left to right on the left, shiny part, then darker part, and then the insulation. Since the wire is only held in place by the force of the rubber, any movement of the wire could cause it to not work properly - this is what I think anyway. This is due to the one contact that has very little room to play.

It was interesting to look at, and should be good if(when?) I decide to make an open source transmitter. After reading the PDF on the how the sensor works everything is sort of falling into place. I'm actually pretty interested in getting a pack of sensors and getting the raw data from them on myself. The article really does explain a lot. I was surprised to read about since there is a delay in the glucose reading for the CGM they use predictive algorithms to determine the actual value. Before I was assuming that they just gave you the reading of a 15 minute delay and were like "Deal with it". Though I still believe there has to be a better way to get fast constant readings. I just know its out there.

Some other news, not 100% yet, but one of the directors of the program I just graduated from, B. Tech, he has been involved with some of my projects before and is willing to put a bit of money in to expand the research in developing an open source transmitter/receiver as well while using dexcoms sensors. So that could help! Won't be a lot, but probably enough to get a transmitter and some sensors. Anything helps really.

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Awesome stuff

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You might find this interesting/valuable: http://www.diabetesforecast.org/2014/05-may/anatomy-of-a-cgm-sensor.html

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For those not on Twitter or following me. (I'm @idlehandsdev) I posted that I received my DexDrip boards I was working on.


They are boards that can listen to your G4 and then send a value to your android device. All in one simple board instead of having to piece components together and what not. Also going to design a 3d printed case for it, keep it slim and tidy for those not able to put their own kit together.

I'm probably going to be pestering my Doctor as some point relatively soon about getting my own CGM. Which should help with developing some of the things I'm working on(and of similar importance, my BG).

Lately I have become very intrigued with those close loop systems that were posted. Its almost making me want to design my own. I'm not sure if I would be brave enough to test it out on myself. And there would be a lot of steps on the way including getting a CGM, a pump, learning to use the pump, all of that. But its totally a possibility.

I should be receiving another transmitter from a member here that is still in working condition! If I can get some working time out of it I can possible test the DexDrip with different resistance values mimicking a sensor.

I've been a little busy with school semester coming to an end in April. So I will need to think about my next plan of attack with regards to these projects. There are several small projects that I could tackle, but I need to see the best place to put my time.

49

A little update, still working on these things slowly. I put the project on HackADay.io - NIRGM - Non-Invasive NIR Glucose Meter | Hackaday.io and entered it in the hackaday prize. Which means potentially I could get funding up to $100,000 to turn the project into a product or do a lot of research. It has been getting a great response. If anyone here is into that kind of stuff please sign up and give a skull and follow the project. It will help.

A lot of responses to people wanted to help as well which is great. Need to figure out a plan on how to procede. I want the project to be open but I also want to make sure it stays on track in the direction that will benefit it the most.

3 Likes
50

Are you still working on a way to reuse the Dexcom transmitters once the battery is dead? I just received my G5 in the mail yesterday and would be more than willing to send you the transmitter once it dies. Iā€™ve been told it has an automatic shutoff at 108 days so even if it has battery life left itā€™s unable to be used. Complete waste in my opinion. Iā€™ve looked at other posts on opening it up to replace the batteries, which I plan to try as well with another transmitter, but thought you may get better use out of it and actually help thousands, whereas Iā€™ll probably hack it to death and trash it! If youā€™re interested please let me know and Iā€™ll mail it to you around the end of January.

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Awesome! Yes you have PM, sorry my other reply I thought I was writing a PM. haha.

53

Hi, is anyone still working on a open source Dexcom Transmitter topic??

I also thought developing a PCB for the Dexcom G4/G5 allthough having a different approach in mind.
I have one of the Abott Libre devices here and it is a single chip solution.
They use the RF430FRL152H from Texas Instruments as far as I can see and they use NFC communication. I think the chip does not need a oscillator and the data is meaured by the integrated sigma delta ADC as far as I understand. This makes the PCB design quite simple. Allthough the device is not real time it has several advantages i.e. it stores glucose data for some hours and NFC consumes nearly no power.
So if someone allready has a solution for the two wire based measurement method of the Dexcom i.e. knows how the electrode has to be driven to measure current of the reaction then it would be nice if he shares the findings here.

@hodginsa
Do you still have one of those prototype PCBs available??? Did you ever get it working???

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The battery replacement in the G5 is fairly simple, as it is not a sandwich PCB. The problem is the software blockage, which kills the receptions from transmitter after approx 105 days of use. xdrip can continue to read it, but I would rather use the original software.

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Hi.
I just found this thread on Google and signed up just to comment because I have been researching this exact project. Iā€™m T1, and I would need to self fund CGM, so this work by @hodginsa is inspiring.

Awesome project.

Sean, may I ask what has happened since your last post in November 2015? Are you still working on it?

Iā€™m also a maker (but nothing like as prolific/proficient as Sean) and I would like to give this a shot myself, on the same open source basis and report back the results. Iā€™m a member of a fablab where we have 3D printers, 3D scanners and a CNC milling machine.

I would like to concentrate on the G5 version, which can communicate directly with teh XDrip software on a phone, without the need for the DecDrip board/bridge.
If anyone has a dead G5 transmitter that I could have or buy for this purpose please message me.

56

Not much has progressed on my end. I made a board with the components populated and was able to put the xdrip firmware on it, but was not able to connect to any of the transmitters that were sent to me. Not having, or being able to afford a working dexcom system made it difficult to test and develop - that plus being over worked from doing my masters didnā€™t make it any easier.

Part way through I noticed the OpenAPS group was working on something in combination with Sparkfun to connect to the intel Edison. So I figured they would have a board developed by now. But I havenā€™t been keeping up with the progress. Maybe look into that?

57

Thanks for the update @hodginsa.
The good news is that the G5 transmitter now uses low energy bluetooth to transmit directly to an iPhone (with the Dexcom app) and thanks to the fantastic work by these guys directly to an android phone with xDrip-plus.

So itā€™s looking like you donā€™t need and extra board or hardware bridge at all, or even the Dexcom receiver for that matter.
Iā€™m trying to get this set up using only a repaired transmitter and xDrip-plus, which only leaves the Dexcom sensors to pay for, and I have made the decision that I owe it to myself to somehow make it work financially.

If enough smart people started working like this on the hardware side, at this rate we could really have a fully open source CGM system.

58

Iā€™ve also been reading @Dave26ā€™s post about getting it directly to a smartwatch with the android wear xDrip plus. It seems you still need the phone for setting up the sensor, but it seems that you can leave the phone behind teh rest of the time and the watch will continue displaying and collecting the sensor data.

59

Yesterday I made my first sensor Change on a G4.
When the sensor was off I took the G4 transmitter device and looked what potential is applied to the pins.
It seemed that each 2 seconds about 1.63 Volts are aplied for a short time which then decay slowly.
I think one possibility to measure nano and picoampere currents is to charge a capacitor and measure the time it takes to discharge. Maybe this principle is applied here. Texas Instruments has an IC, the DDC114, which works this way.
It would be interesting to see if it is possible to measure the current flowing through the sensor with the integrated ADC of a microcontroller this way.

Next time I will try to catch the voltage on a Oscilloscope.