Happy Howlidays (hur hur)

For my next project I thought I’d try to keep it simple and check out a holiday card I received (as I found out, it’s probably a better idea for me to look at more complicated devices…).

This card has a button in the top left that plays “Jingle Bells” using barks (Figure 1):

Figure 1: Overview of the card

Once you open the card, you can see the rough outline of where some of the internals are — I tried to outline it a bit with a pencil (Figure 2):

Figure 2: Inside the card

Carefully opening this up with a razor blade, we see a small motor, a button, a speaker, and the board it’s all hooked up to (Figure 3):

Figure 3: Card components

The small board is laid out pretty nicely, actually — pretty much everything was labelled:

Figure 4: Main board

My main issue at this point is that since this is such a cheap piece of hardware (kind of crazy to think that this entire thing is meant to be disposable, basically) it’s another chip-on-board based system:

Figure 5: Chip on board close-up

Looking at this and the rest of the board, I was able to find what appear to be be 8 pins — V0, V1, P1, P2, SDA, SCL, VSS, and one that’s a bit too obscured by the packaging material to be read. Trying to search for 8-pin microcontrollers or ICs isn’t really getting me anywhere. Seeing that there’s just SCL and SDA, I’m thinking maybe it’s I2C, so I tried hooking up the logic analyzer and seeing what comes out when the button is pressed. I managed to capture some output coming from the chip towards the speaker as well as the SCL activity, but nothing really too interesting for me at this point. I think I’m going to move on and try to look at something with a bit more stuff on it for me to look at — like maybe some actual ROMs I could dump. I thought I’d be getting a better start by looking at these really simple things, but I think that they’re a bit too simple for me to get much out of it at this point.

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