I'm playing catch-up to document a week's worth of late nights. This is the version 0 of the CoinOp badge schematic before doing any layout. I based my parts choices on the following:
- Cheapest TQFP microcontroller I could find with as many pins as possible. I found some ATmega48 chips on Digikey for $0.70 at low volume and this is less than using constant current drivers.
- Coin-cell battery (CR2032). They're cheap and easy to find. I'll be somewhat limited on current by directly driving from the uC but this battery doesn't have much juice so the two are a good pairing.
- 3 red LEDs for each blaster so I can do a back to front animation
- 2 blue LEDs for each shield
- 4 red LEDs for each engine. I've run out of pins so I used a charlieplex for these
- 2 buttons, one will be used to wake from sleep. I decided to connect these to VCC and us an external pull-down resistor so that I'm not burning the internal pull-up during sleep mode. If my power-down mode sucks I've also included a 2-pin pad that is shorted. I can always cut the trace and put a pin header so that jumper can be used to disconnect the battery.