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Designing myself a good watch.
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datasheets POCSAG docs. #118 Apr 14, 2019
firmware Better tracking of how POCSAG messages are received. Apr 20, 2019
hardware Added a BOM entry for the 868MHz filter. Nov 15, 2018
photos First photos of the device. Apr 12, 2017
website Better makefile for the website. I ought to rewrite the infernal thing. Nov 3, 2018
.gitignore Updated .gitignore. Aug 29, 2018
Jenkinsfile Jenkinsfile to test firmware and energy consumption on real hardware. Sep 26, 2018 Manual merge. Nov 11, 2018

Howdy y'all,

This is a side project of mine to build a replacement circuit board for the Casio 3208 module, used in the Casio CA-53W and CA-506 calculator watches. It is not compatible with the 3228 module used in the Databank watches, which have four external buttons instead of two. As a side project, it has no warranty whatsoever and you shouldn't use it for anything.

In the rare case that you find this project to be useful, you owe me a pint of good, hoppy pale ale. All license to use this project is revoked if you try to pass off a pilsner instead.

In addition to the source code, there is handy documentation in the wiki and a general interest website at

73 from Knoxville,


Software Status

Our firmware is freely available in this repository, compiling with the standard MSP430 compiler packages that ship with Debian. It consists of a Clock, a Stopwatch, an RPN Calculator, and a Hex Memory Viewer with Disassembler, all written in C. It compiles in Debian with all of the MSP430 packages installed.

On watches with a radio, we have Morse and GFSK transmitters, as well as an OOK transmitter that will command cheap remote-controlled relays. It has a frequency counter. The radio is accessible from a host computer over the UART for building base stations and repeaters, or for rapidly prototyping radio applications in Python. P25 and DMR support might come soon.

Additionally, we've written our own client for the CC430's BootStrap Loader (BSL). You might find it handy for other projects involving that chip, or other MSP430F5 and MSP430F6 chips without USB. You will need to be a member of the dialout group to flash the firmware.

Firmware documentation can be built with Doxygen.

Hardware Status

Our replacement board is based around the CC430F6147, which combines an MSP430 microcontroller with an LCD controller and a sub-GHz radio. Thanks to pin compatibility, our fancy linker scripts produce a firmware image that works just as well on the older CC430F6137 chip.

The GoodWatch30 is our current hardware revision, with filters that run from 300 MHz to either 500MHz or 915MHz. The GoodWatch20 family had narrower filters at 433MHz, but is still supported.

See BOM.txt in the hardware directories for a parts list, and the wiki for an assembly guide.

Related Projects

Pluto is a replacement PCB for the Casio F-91W that is also based on an MSP430. We happily use that project's energy monitor utility for measuring our power budget.

FaradayRF is a CC430 radio board intended for amateur use, with a 500mW amplifier and GPS receiver. Their radio chain is far more carefully designed than ours, but in time, we hope that the two projects will communicate with each other.

openchronos-ng-elf seems to be the most recently maintained firmware for TI's OpenChronos devkit, which uses the CC430F6137.

The CharlieWatch from Trammell Hudson is a nice little fork of the GoodWatch that uses a charlieplexed array of LEDs instead of a Casio watchcase.

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