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Battery-saving Analog Watch Face (BAWF)

Version 0.2, September 2023

Screenshot

This is an extremely simple, non-configurable watch face, originally for the Garmin Vivoactive 3. It may work on other Garmin products with round faces, but all I've tested with real hardware are the VA 3 and Venu 2.

The same code can build white-on-black and black-on white version of the watch face. White-on-black is probably better on OLED devices like the Venu 2, because there is no backlight. On LCD devices, colour makes no difference to battery life.

The sole purpose of this application is to present an Analog watch face with the minimum amount of power consumption, to extend battery life. To that end there is no seconds hand, no dynamically-generated fitness information, nothing except time and date. I've been very careful to ensure that the amount of math required to draw the face is minimized, and repeated calculation avoided.

Thirty-party watch faces for Garmin fitness products are frequently blamed for causing battery drain. It's very easy to implement a watch face carelessly, so that it does too much work, too often. Anything that displays a second hand will need to redraw at least part of the screen every second. This watch face is generally updated only once per minute.

Building

If you're reading this, you probably already know how to build ConnectIQ watch face apps.

I build at the command line like this:

monkeyc -o bawf.prg -y /path/to/my/certificate.der -f ./blackonwhite.jungle -d vivoactive3

This builds a version with black figures on a white background. There's also a whiteonblack.jungle file to build a white-on-black version.

Instructions on building at the command line are here:

https://developer.garmin.com/connect-iq/reference-guides/monkey-c-command-line-setup/

To run on the simulator:

monkeydo bawf.prg vivoactive3
monkeydo bawf.prg venu2

Installing

To install on a watch, just copy bawf.prg to the /GARMIN/APPS/ directory when the watch is mounted as a USB drive.

Change history

0.2 September 2023

  • Bug fixes for Venu-era devices (Garmin has made breaking changes in the Monkey C API!)
  • Added support for white-on-black, particularly for OLED devices.