Hi Luke, thanks for the driver, just tried the latest code with my Drillbits, I have 2 issues:

1. Stats is unavailable for thumbs, so bfgminer causes lots of "Short read in response to 'T'" error.
Just adding a "if (dev->procs == 1) return false;" in drillbit_get_stats fixes this for me;

2. The range for external clock should be wider, many people overclock Thumbs to higher than 230.
Currently cgminer driver do not limit it, just prints a warning when lower than 80 or higher than 230.
Angus of Drillbit Systems had suggested to try 250 for up to 3GH/s with active cooling and enough power (1000mA).