3 ms·

Or just reporpose an old phone.

• mseebach 9y ago
  I was thinking about this in terms of building a product. Even with that, a clock generally runs for months, even years, on a single battery. Not exactly phone territory, but might be feasible on the ESP8266, depending on how the oscillator behaves in deep sleep mode.
  • c3833174 9y ago
    >how the oscillator behaves in deep sleep mode. horribly
  • sokoloff 9y ago
    There are many dedicated real time clock chips, pre-designed for backup time-keeping and low power usage. Interfacing with one is going to be way faster/easier/better than trying to roll your own on a general purpose microcontroller, IMO. TI's bq32000 is $0.55@1K, is 3.3V for easy interface to the ESP, and takes just over 1 microamp in backup power mode. That's just one that I quickly poked at. (Side note: at this point, I'd think I'd want to be using an ESP32 in any new designs.)