D21 led smartwatch design help ???

Official Hardware Classic Zero
1

Hi, I want try design smart watch with segment display.

But I have no experiences with ARM ...

Why led display???

  1. because is retro and retro is now cool

  2. On maket is millions of lcd, oled, epaper watches
    then millions smart-bands with 3 leds .... and nothing between ?

  3. I want show another way :slight_smile:

... you can see may work here ...hackaday.io
or on video ...youtube

Why samd21 ?

  1. sketch with alarms, sunset sunrise calculator, speech output is is now about 31kb on atmega328.
  2. D21 ... lot memory
  3. officially supported in arduino IDE
  4. usb bootloader for updates
  5. DAC

What I need know ?

  1. lowest Stand-by consumption with RTC or without
  2. how go to sleep and how to set interrupts to wake on any pin
  3. how to play wave file from internal memory(sd card)
  4. how to change PWM frequency
  5. power consumption
    ... some ideas ...?

Thanks.