Unlike a lot of other software or controllers, you don't even have to know what does what in midi cc for the 225e to do it's magic. Much like patching a cable from point A to point B you simply need to dial in the number of the controller you want to use, tell it what jack to come out of, and then you are free to go back to CV patching with banana cables just like every thing else on the 200e but with the added feature of being able to use any midi controller pad, sequencer, bit of computer software, etc.
Given the wide variety of freeware programs and affordable Apps this opens up a brave new world to interface with or control the 200e. There are VST or midi sequencers, dedicated LFOs, and even things like hardware midi delays and arpeggiators that can trigger, sync, or modulate the 200e on it's own terms.
Last post I used an IPad to send note and gate info as well as tweak the volume and filter sweeps. Here's a short video showing how easy it is to set this up in the 225e.
If you've never wanted to use midi or felt it wasn't worth your time (I've been in both camps and am still not a huge fan of midi) this might be a good starting place to add to your 200e in a powerful and very affordable way. Given the fact that Buchla and Assoc made the 225e such an integral part of their 200e design and philosophy ignoring this is missing out on a large part of owning a new Buchla. The good part is you don't need to learn a lot of tech stuff or have binary computer programming skills to take advantage of the great features the 200e offers. Back in the day you used to have to know sysex commands and language to send start and stop strings of code to do anything. Thanks to the mix of modern and classic (a common Buchla way of looking at things) all you need to know is how to use a patch cable and a programmer than is as easy as the 200e preset manager.