David Hamp-Gonsalves writes:

I bought a robot cat litter box called the CatGenie 120 and it was great… until I realized that the helpful low soap warning was actually DRM which blocks all cleaning actions once its official soap cartridge is “empty”.

David goes on to discuss his foray into reverse engineering including snooping on I2C busses:

From the datasheet I knew that the main device was communicating with the CR14 RFID reader via I2C. I had learned about cheap logic analyzers and Sigrok from the podcast so I ordered one off of AliExpress for 5$ and waited. Once it arrived I ran into a series of issues. First the wires that connect to the chip used incorrect colors (I think to be misleading) and combined with this being my first time using a logic analyzer it took me awhile to figure out. After that my lack of knowledge about I2C and signal analyzers sampling rates caught up to me and killed another few days of free time.

Eventually I got everything working and recorded my first accurate signal capture:

Read the entire post on David’s blog.