Now that we’ve figured out how the jumpers work, let’s try to figure out what the pins do. To start, let’s give them numbers.
Pins 1, 4 and 8 are the pins that are used for jumpering (see last post).
Using an oscilloscope, no signals appear on pins 4 and 8, but spikes 30 ms apart appear on 1. Perhaps this is use to signal the Tamago that a figure has been attached.
Nothing seems to be happening on pin 2, but the figure doesn’t work if it’s covered. I’m going to guess that it’s power or ground.
Pin 3 gives some rather glitchy square waves. Alex W suggested that figures might use I2C (I’m assuming they have a mask ROM inside), so this might be the data line of I2C.
Pin 5 has no signal, and the figure is not detected at all if it’s covered. It might be power or ground as well.
Pin 6 has some very clean square waves. The waves are 300 us wide. It is by far the cleanest signal. This could also potentially be data (the waves aren’t uniform).
Pin 7 contains noisy square waves like 3.
It also outputs an odd waveform when not in use.
So it looks like three pins have square waves on them, so there are three possible lines for I2C (and one would be an echo), or perhaps the ROM responds to something altogether different. Regardless, the frequency looks like it’s about 3.33 kHz.
Next time, I’ll hook it up to an arduino, and try to decode the signals better.