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uWatch on wrist showing time

µWatch unofficial FAQs[edit]

The uWatch is an RPN and Algebraic scientific calculator watch that you can build yourself. The software is open source under the GPL license at Sourceforge. I'm assuming you've already read the official uWatch FAQ, so we'll jump right into some more technical details.


See Open Source Watch

The OSWatch and the uWatch are both open-source wristwatches that are fully user-programmable.


See watch display

The display is perhaps the most critical part of a wrist computer such as the uWatch and the Open Source Watch.

The history of the uWatch mentions the 53mm x 20mm compact 16x2 line LCD that convinced David L. Jones that the uWatch project was actually doable with off-the-shelf components. If you are doing low-level programming of the uWatch, such as making "custom characters", you might want to look at the datasheet (via "Moon Phases").

Alas, that original display pulls about 2 mA, more power than anything else on the uWatch -- even the CPU uses less power (at 250 KHz). That's the main reason the current uWatch cannot run the display continuously (like a standard watch), but much be explicitly "turned on" every time you want to read the time.

The current uWatch2 rough draft seems likely to use the Newhaven NHD-C12832A1Z-FSW-FBW-3V3 128x32 Pixels display. Which uses less than 100uA which would enable a continuous display watch. The "white LED backlight" uses 30 mA at 3.0 V but is still very usable at much lower currents.

There's some discussion of some of the screens considered for the first iteration of the Open Source Watch at http://oswatch.org/details_screen.php .

Proposed displays: Limited to less than 10 mW of power when updating the time once a second (FIXME: reduce this limit and prune higher-power displays when this list gets too long): In no particular order:

Some threads discussing diplays: "Hardware Stuff » Why not a smaller LCD...",


The buttons are crucial for a calculator watch. It is difficult to compromise between:

  • fast typing speed:
    • it's much faster to have lots of buttons, so you can directly push a button for "tan" than to scroll through some soft menu searching for it.
    • large buttons are generally faster to rapidly punch than tiny, closely-packed buttons
  • physical size:
    • We want something that is not too heavy and bulky to wear on the wrist. This means lots of large buttons are not going to happen.

The first uWatch prototype used surface-mount buttons. The original uWatch for sale uses the (through hole!) Panasonic EVQ-PJG05Q switch for its buttons. [3] (current price)

  • please tell us about other buttons that would be appropriate
  • ... capacitive touch "buttons" ? ...
  • ...


The processor is, perhaps surprisingly, not a crucial choice. In the last few years, several companies have released processors that meet the stringent low-power and other requirements (which are????). In theory, since most of the software is written in the C programming language, it is theoretically easy to port the software to a different CPU.

The original uWatch uses the 16 bit Microchip PIC24FJ64GA004. It uses 50uA at 32KHz, ... (FIXME)... uA at 250 KHz.

Other proposed processors have been discussed on this thread: "Hardware Stuff » Ideas for Mk2 watch".

... the Microchip "Extreme Low Power Microcontrollers" claim to have "Real-time Clock/Calendar down to 500 nA". http://www.microchip.com/xlp

Nate gives some low-power tips in "Adventures in Low Power Land".

Arne Martin Holberg and Asmund Saetre. "Innovative Techniques for Extremely Low Power Consumption with 8-bit Microcontrollers".

Other open-source wristwatches[edit]

(FIXME: should this list go on some other page?)

"IS YOUR WEARABLE TECH TOO SUBTLE?" "My 3D-printed Big-Ass SmarTwatCh" http://zackfreedman.com/2014/07/19/my-3d-printed-big-ass-smartwatch/ https://hackaday.com/2014/07/19/wearable/ "Arduino-based, has a breathalyzer, and is not subtle!"

"Introducing the F*Watch, a fully open electronic watch" https://hackaday.com/2014/10/17/introducing-the-fwatch-a-fully-open-electronic-watch/ "The watch is powered by a 500mA LiPo battery. All the tools that were used to build it are open source (FreeCAD, KiCad, GCC, openOCD, GDB) and our readers may make one by downloading all the source files located in their repository." http://www.ohwr.org/projects/f-watch/repository

"DIY OLED smart watch" https://hackaday.com/2014/07/07/diy-oled-smart-watch/

"Make your own smart watch" https://hackaday.com/2014/02/17/make-your-own-smart-watch/

"a bracelet that allows you to strap your raspberry pi to your wrist." http://www.3ders.org/articles/20130604-lighting-up-graduation-with-an-awesome-3d-printed-web-connected-led-cap.html http://www.damngeeky.com/2013/06/11/11891/3d-printed-control-my-cap-is-perfect-to-light-up-your-graduation-night.html

"a working prototype of Fallout's Pip-Boy 3000" http://singularityhub.com/2014/05/08/inspired-by-video-game-makers-construct-wearable-wrist-computer-for-space-explorers/ (appears to be more functional)

"A fully 3D printable Pip-Boy 3000" http://www.3ders.org/articles/20130630-a-fully-3d-printable-pip-boy-3000.html http://www.geeky-gadgets.com/diy-3d-printed-fallout-pip-boy-3000-wearable-created-10-09-2015/ (far more "realistic", painted to look "weathered")

"GyroPalm" http://3dprintingindustry.com/2015/07/14/3d-printed-gyropalm-seeks-to-control-your-electronic-world/ includes infrared and inertial measurement sensors. "the GyroPalm is open source and 3D printed"

"Smartlet: go on, wear your iPhone on your wrist" http://www.thecrowdfundnetwork.com/smartlet-go-on-wear-your-iphone-on-your-wrist/

"DIY Digital Wristwatch" http://blog.zakkemble.co.uk/diy-digital-wristwatch/comment-page-1/ https://github.com/zkemble/NWatch

"Homebrew smartwatches" by: Brian Benchoff http://hackaday.com/2015/08/12/hackaday-prize-entry-homebrew-smartwatches/

"Get up, stand up. with a little help from the mindfulness bracelet" by: Adam Fabio http://hackaday.com/2015/06/16/get-up-stand-up-with-a-little-help-from-the-mindfulness-bracelet/ (it technically keeps time, but it doesn't display time visually ...)

"Ben Heck’s Oscilloscope Watch" https://www.youtube.com/watch?v=HOqBInoDEhE modifies a Xprotolab to make a functional o'scope worn like a wristwatch. Places battery pack in the strap rather than under the display, and other techniques, to reduce maximum thickness, to achieve the goal of "keep watch under 1/4" thick (about 7 mm)". The firmware and PC interface software are open-source.

further reading[edit]

Late breaking news: there is now another µWatch wiki; is that the Official µWatch wiki? Feel free to move all the content on this page to that wiki. --DavidCary 15:58, 19 November 2009 (UTC)

Oops, that wiki has gone offline. So we'll keep this wiki page at Open Circuits. --DavidCary 23:08, 4 September 2011 (UTC)