Hi,
I have my own USB CNC controller ( something close to ncPod - 120Mhz Arm Cortex CPU capable of about 100kHz operation). It works with different software then Mach.
I wanted to to write Mach plugin for it, but there is no good documentation for it. There are few people who know it quite well, but this knowledge is commercially valuable , so nobody was interested to join me.
I have it quite alive. There are few things missing ( like input/output processing, homeing, jog operation), but basic motion works. There is also console windows to dump all interesting internals
I decided to share it before finishing as there are some other people working on similar design (
http://www.machsupport.com/forum/index.php/topic,17602.0.html)
So - please have a look at sources, play with it.
It is free to use as long as you share your knowledge to make it really good template for starting own motion plugins.
You need Visual C++ Express 2010 to compile it.
You will need to change in project post processing step - to accomodate path to your Mach directories.
In case your console window is too small - change it . Once changed it will keep setting for consequiteve runs.