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TOTP tokens on my wrist with the smartest dumb watch

(blog.singleton.io)
274 points alexmolas | 2 comments | 26 Jul 24 19:20 UTC | HN request time: 0.451s | source
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matheusmoreira ◴[27 Jul 24 07:20 UTC] No.41084977[source]▶
Love this project, use it literally every day.

Not too long ago I implemented a new interface for defining the TOTP codes from within the source code. Unfortunately that work has invalidated the instructions in this article. It works like this now:

  static totp_t credentials[] = {
    CREDENTIAL(2F, "JBSWY3DPEHPK3PXP", SHA1, 30),
    CREDENTIAL(AC, "JBSWY3DPEHPK3PXP", SHA1, 30),
  };
https://github.com/joeycastillo/Sensor-Watch/blob/main/movem...

I also added user calibration to the pulsometer in order to allow it to be used as an asthmometer. It has already helped save lives.

It's also got calibration and thermal compensation features which enhance the watch's accuracy to about 10 seconds per year.

It's got a growing community. A lot of people have showed up to hack on the firmware. Recently someone made an endless runner game for the watch:

https://github.com/joeycastillo/Sensor-Watch/pull/419

The maintainers are really nice people too.

If you're looking for a great open source project to sink some time into, this is it.

replies(1): >>41088704 #
1. thomasbbrunner ◴[27 Jul 24 19:23 UTC] No.41088704[source]▶
I imagine you'd use a common watch battery to power this. Can you comment on the battery life? Could not find it in the docs.
replies(1): >>41089686 #
2. matheusmoreira ◴[27 Jul 24 22:11 UTC] No.41089686[source]▶
Same battery as the original watch. Most of the watch's parts are reused, including the battery clip and the battery itself. Only the circuit board is replaced.

The original module lasts about 10 years on a single coin cell. The sensor watch can't match that incredible lifespan but it's still very respectable. Power profiling and testing has shown that it has over a year of endurance. There's a builtin battery voltage sensor which serves as a power reserve meter. Maximum power would be 3 V and low power would be something like 2.2 V.

I modified the low power mode timers to make it go to sleep after ten seconds in order to extend it as much as possible. Low power mode means the CPU wakes up once per minute instead of once per second. The only drawback is the lack of seconds display but the truth is I've come to consider that a feature. If I want to know the seconds, I push the alarm button to wake the watch up.