Impact Monitors

After Solbourne left the hardware business a couple of ex-Solbournites, Ty Sell and Mark Thomas, and I did some consulting before starting an engineering services company called Bolder Design Labs (BDL). We primarily provided ASIC verification services. While I had that gig going my wife had become involved with a small medical device start-up. I ended up helping them design a product for use in limited weight bearing regimens called the ForceGuard. It used a very simple PIC microcontroller and some analog electronics to measure the pressure exerted on a cleverly designed in-shoe footpad filled with Fluorinert (the stuff used to cool the Cray-2 and also used in the simulated liquid breathing system in the movie "The Abyss").

Although the firmware was fairly simple (about 4 Kbytes) it had to get FDA approval as a class II medical device. Lots of records, module-level testing and system testing. It actually made me think about the process of software development like never before. The firmware was a big state machine so I could avoid using interrupts but still keep up with the real time activities using a very slow processor clock (32 kHz / 8192 instructions/second). The device would run months or years on a set of batteries. I enjoyed working with my wife and we did really well together. It was a pretty big load doing this project as well as my full-time work at BDL.
Impact Monitors system
PCB
The wire was added to force the PIC into reset as the unit was switched off to prevent errant writes to an EEPROM.
Brochure