Mayavi

Watch will feature an "etch a sketch " mode...

With Nordic UART Service and a simple text command, can now set time...

Since we have two buttons, I think Mayavi will have a drawing mode - like an Etch A Sketch. Double taps can clear the screen thanks to accelerometer...

Almost done with schematic...

This will do, and I can skip the 32 kHz Xtal...

This should help me with coding. Made with draw.io...

Moved to nRF5 15.0 SDK. Added LIS2DH12 accelerometer driver and GPIOTE support for button presses. Code pushed...

Started prototyping the project with nRF52-DK. I had previously ported the Adaruit GFX and SSD1306 libraries to nRF52, so getting a counter up and running wasn't too hard...

...everything looks like a nail.

I put some thought into what controller I should use for the watch, and what it should display. 

My initial idea was to use an AtTiny chip. Then, I though that an AVR might give me a bit more flexibility, Arduino bootloader, etc. Well, then why not an ARM? SAMD21 will do nicely. Finally I thought - I'll just use an nRF52832 - ARM Cortex M4, gives me BLE to fool around with, and that's the platform I am most familiar with anyway.

Also, after thinking about LEDs, bubble displays and tiny 7-segment displays, I decided on an OLED since that gives the possibility for some fun graphics.