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 download and run the generator through a local web server, and view the page using google chrome, you can even program the MPG-200 directly from your browser.
The full PG-200 protocol is described in detail here