The MPG-200 is a midi to PG-200 protocol converter. It lets you use any midi controller or DAW in place of the expensive PG-200 controller for the Roland JX-3P or MKS-30.
The MPG-200 is highly configurable through Sysex. Each parameter is mappable to any Midi CC, and switch range boundaries are individuably mappable for each switch.
A sysex file generator can be found here. It lets you tweak the parameters and generate a valid configuration sysex. If you're running Google Chrome you can even run the sysex update the MPG-200 directly from your browser.
A firmware update system can be found here.It lets you update the MPG-200 firmware over midi. It only works if your browser supports WebMIDI (I don't know if other browsers than Google Chrome do).
The full PG-200 protocol is described in detail here