Reverse Engineering an Insulin Pump for DIY Closed Loop Therapy #Diabetes #Diabetic #ReverseEngineering @PS2
Pete Schwamb writes recently on Noteworthy about Insulin Pumps, Decapped chips and Software Defined Radios:
Roughly 3 years ago, I heard about a website offering a bounty for something that was very close to my heart: reverse engineering communications to an insulin pump. My daughter was already using a system that I had helped to create called Loop, with a Medtronic pump that I had reverse engineered the RF comms for. But the Medtronic pump required her to disconnect during her gymnastics for hours at a time. The tubeless design of this Omnipod pump sounded great, and I had all the tools to start working on the problem.
The Omnipod system consists of a small disposable pump called a pod, and a controlling unit called a PDM.
Because the PDM communicates with the pod using radio and the pod has no built in interface, it means the pod is entirely controllable over the radio. There was the potential to create a full integration with Loop using just a RileyLink, or a modified version of it.
I had to write new firmware that would handle the pod modulation and encoding. I also had to rewrite the way the two chips on the RL talked to each other to handle 0’s, as 0 was a special end of packet marker for Medtronic (pumps). Much in Loop needed to be reworked to support multiple Pumps, and new interfaces made to support pairing, deactivating, and handling faults. Thankfully Nate Racklyeft had set a solid foundation in Loop for this to happen.
New Features For Loop
Omnipod integration required rethinking of some interface elements, and adding new controls. The pod doesn’t report battery, and there is little a user can do about a low battery if one were to somehow happen, so displaying a battery level widget didn’t make sense. Also, without a UI on the pump, the user needs to be able to cancel a bolus quickly. The reservoir icon was a picture of a Medtronic reservoir, so we wanted to rethink that. Thank you to Paul Forgione for designing the pod logo that now shows reservoir level.
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