I plan on programming my boards using ArduinoISP from my Arduino UNO, so I thought I would get a jump-start on firmware development and testing an ISP setup by building a breadboard prototype of my circuit (as I've always programmed over UART in the past).

I soldered together a little SIP ISP programming header, and set the fuses of a DIP ATmega328P with Optiboot I had laying around to run with the 8MHz internal oscillator (since I didn't have a 16MHz crystal on hand, Nick Gammon's wonderful Arduino tools helped me out with an alternate clock source). On the actual board, I plan on using the 8MHz oscillator for the CPU, and running a Timer2 RTC with an external 32KHz crystal. After laying things out (including a button to simulate the touch sensor), a simple test program (blinking one of the Charlieplexed LEDs) worked great:

After some research into more easily controlling a Charlieplexed LED matrix, I went with Alexander Brevig's Charlieplex Library. This allowed me to run a more complex test with all of the LEDs, and had a great design for storing matrix pairs in an array of structs, but a bug quickly surfaced that could affect minimum refresh time on larger displays - If I didn't clear() the display before switching an LED on every time, then multiple LEDs were lit (which means that not all of the 6 control pins were truly driven into high-impendance "disconnect" upon writing a "low" using the library's charlieWrite() function). I modified the library to my liking, including the fix to this bug (writing both control pins for an LED to high-Z disconnect - input mode written LOW - upon writing the LED to "low" using the library).

Next was to figure out sleep modes and pin-change interrupt wakes via the touch sensor. Nick Gammon's tutorials were again extremely useful, and got me up and running with a writing registers for interrupt setup. I can't test anything I write for the Timer2 timekeeping interrupts until I assemble a prototype board, because I don't have a 32KHz crystal on hand, but that and ultra-low sleep modes are the next steps. I also would like to allow shorting of some of the ISP pins to 3V3 to allow for setting the "time" in case of power failure or reset...

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Videos are taken, but not yet hosted anywhere - they'll come later.