From a technical perspective I found this story compelling, so I tried out a simple hack to see if it were "possible". Using an attiny85 uC, a couple resistors, a cap, and a couple diodes I had laying around, I was able to wire up a two terminal "device" that pretty much acts like a 5k pull up resistor on a I2C line.... But when you pass data through the signal line (SDA) wire it can read and modify it. It is crude a…
How did you get an ostensible power terminal (for pull up) and two terminals for MiTM (input and output) from two terminals? Assuming a situation where there are other pullups on the wire, how did you assert the low state (short to ground) without a connection to ground?