Thursday, July 11, 2013

Getting it Smaller

Took a shot at reducing the case size.  The large version(7"x5"x2")  is good for 7.5 hours, and is nearly indestructible.  The small case is a tiny fishing tackle box, the size of a match box(5"x3"x1.75"), good for 2.5 hours.  I've left a USB cord attached to it, so it can be plugged in whenever possible.  Decent for trips to the gym.

5" long is as small as you can get and fit the Dexcom with it plugged in.  Had to special order a 90 degree micro usb plug. 

A picture of the inside of the box.  The battery is underneath.  The switch allows me to charge the battery while still running the PI.  Not sure what's with this brand of battery/charger circuit(enercell), but it shuts off power when charging.  The PI has been extensively modified.  I've cut off just about everything that sticks up.  Also, relocated the USB ports.  Allot of time was spent with a magnifying glass doing this work.  I've also shortened the numerous USB cables.  You run out of room fast with extra cord length.  USB plugs were also shaved with a razor blade to make them lower profile, and more bendable.  Power is supplied to the PI via the GPIO pins, since I didn't have another 90 degree USB.  Also removed the case from the battery, which freed up 1/8", allowing the Dex to sit on a plastic plate, and not directly on the circuitry beneath.

Did some additional tests with the Chronos, battery life is shorter on the transmitter side then using bluetooth.  So the Chronos is entirely out of the picture now.  

Monday, July 1, 2013

A fully functional Dex Watch...

Finally got this running on a Raspberry PI, so it's portable.

This is a waterproof Otterbox.  Costs about the same as the Raspberry PI.  The PI is underneath the Dexcom.  Some modifications were made to the PI with a dremel!  I removed the audio out and all the pin headers, to allow the battery to sit flat in the case.  The Powergen battery gives about 7.5 hours.

I'm now using the Metawatch.  This is the only Waterproof smart watch on the market(at this time).

There's still mud on the watch from its first enduro.

I was also hoping for increased range, between the PI and the watch, but I'm not really getting that.  The range is maybe a few feet greater than the TI Chronos.  What I do get is an easier to use API for the watch, and the ability to make the watch buzz, for low and high alerts.  That's glucose on the left, the minute the reading was taken on the right.  Also, in the center I show up or down arrows for rapid rise/fall rates.  The minute indicator is so I know if things aren't working.

Initially I wrote everything in C#.  Then I ported it over to Linux on my laptop.  In Ubuntu Linux, I was unable to communicate with the Dexcom using the driver that Linux chose.  Luckily, when I tried this on the Raspberry PI, the driver that loaded there, worked fine.

Getting the Metawatch working was also a challenge.  I ended up using a python script ( that is publicly available.  The C# drawing routine that I was using to generate the bmp for the display wouldn't run on the PI, so I ended up making a call out to imagemagik.

This is it for now.  I'm still not thrilled with the overall size, but it works for me.  I think it could be feasible to use a jail broken iPhone 5, the major hurdle would be the USB driver.