Design review / thoughts

[Mike Grusin]

Hey Mary, I hope you're feeling better!

This is a REALLY cool concept, I love the geometry and the layout! I think this will be totally successful when you're done with it.

I don't see any obvious problems in the schematic, so I'll talk about a few design paths you might consider depending on your near-term (get through this workshop!) and long-term goals.

If you're looking to prune the BOM for cost savings, I just brought up a SAMD21 with surprisingly few external parts (e.g. no USB HOST stuff), see the attached 4x4 button pad schematic for details. I'll also attach a schematic for the LilyMini, I was pretty proud of the power circuit that uses a MOSFET as a "perfect diode" to switch seamlessly between USB and a coin cell. I do think that if you're going to include a rechargeable coin cell, you should add a charger chip to charge it via USB (if not for the workshop version, then definitely for the production version).

Since the MSGEQ7 seems to be EOL, maybe just run the audio out of your mic/amp to an analog input on the SAMD21? It should be fast enough to sample audio frequencies. I think the SAMD21 has a true analog output as well if you want to run it through an amp to a small speaker in the future.

In general, the SAMD21 has quite a bit of horsepower and may be able to take over the functionality of some of the external parts like the haptic driver (replace it with a simple transistor driver and let the SAMD PWM it as needed). This would lower the cost, but shifts the hardware problem to software...

Since time is so short, I'd consider simplifying the boards as much as you can for this workshop, and use the workshop experience as beta-testing to help direct the next version.

I'm really excited to see this brought to life! Good luck and let me know what I can do to help.