Casio Watch Hacking

Today I circumvented some questionable business practices from Casio by hacking some hidden features on a couple of their watches.

Background

I wanted a cheap digital watch. Something with alarms and a stopwatch. The Casio W-800H-1BV fit the bill and looked pretty snazzy. It also offers dual time support, which I've kind of been wanting as my work life progressively revolves more around UTC. It also supports calendar functionality like date tracking and day-of-week display. Seemed like a good choice.

I purchased one from Amazon, and it arrived today. The 1BV is the 'blackout' version which features a negative screen; white text on a black display. It ended up being a little bit hard to read, but I was making peace with it.

The Hack

At some point while researching how to use the new watch, I found some Youtube videos that mentioned you could break some solder connections in the internal module to enable a 'countdown timer'. I figured that could be useful so, why not give it a shot?

After work I grabbed my tweezers, opened up the watch, and went to town. A bit too hard, it turns out. I removed the solder connection, successfully enabling the countdown timer, but I somehow broke the speaker in the process. When I re-assembled the watch, it didn't make any noise. Which kind of defeats the purpose of having a watch with alarms.

So, I went to Walmart after dinner to see if I could find a similar model with the same internal module to replace it. I found the non-blackout version of the same watch, the W800H-1AV.

Bought it, took it back home, and tried again. This time I did things properly, with a soldering iron and wick, and removed the solder without scratching up the PCB.

While I had the watch open, I noticed several other solder pads. I did some research and found that you could short one of them and get 5 alarms instead of the usual 1. Neat. So I did that too.

+-----------+
|    +-+ o  | <- open this to enable countdown
|    +-+  o |
|         o |
|         o | <- short this for 5x alarms
|         o |
|         o |
+-----------+

Crude rendering of the control module. `o` represents solder pads. `+-+` represents the logic controller

I ended up swapping the 1AV's non-blackout screen into the 1BV's blackout case, and slapping an old expansion band I had laying around to complete the project.

I'm not sure why Casio designed their modules this way. I suspect it's cheaper to just produce the same modules but solder things differently for different models. Which is a bit lame, but it made for a fun project this evening nonetheless.