There are many things that make this project easy-er to build. That I happen to have a Teensy 3.6 in a drawer goes pretty far. I've also worked with the Arduino SD Fat library, in the past, to perform high speed card writes. Turns out Bill Greiman has updated the tools. His example will benchmark the write time (I added benchmarking the analog read time) and print out the stats of every record session including any overruns. It also has a section for acquiring data that reads analog pins. I'm using analog sensors, so that's not even a lift.

I have 5 sensor inputs. Two Pulse Sensors, and the three axis accelerometer. Acquiring and writing data always takes time, so it's important to verify a jitter 'free' sample clock. In order to do that, I'm toggling pin 24 on every sample. It should output a square wave that is half the sample rate. This is a 'sope of the pin.

Pin toggle on sample. should be 1kHz. SPS is 2kHz

Greiman's example also has a tool to convert the .bin file to .csv file. Dang.

I think the interface will be primarily via computer serial port.

I want to add a button to at least initiate a record session.

Also, some LEDs to indicate that the thing thinks it knows what it thinks it's doing.

The good news is that I have all the parts laying around, and I can print a case in house.

More pics on the next log.