Macraigor has introduced a tiny full-speed JTAG (IEEE Standard 1149.1) or BDM (background debug mode) debugger that essentially converts a JTAG header to a USB header.

h**p://linuxdevices.com/news/NS7199991898.html

and also
h**p://www.macraigor.com/usbDemon.htm

The usbDemon™ is a mid-cost interface used in the design, debug, and programming of microprocessor based embedded systems. One side of the usbDemon interfaces to the USB port of a host IBM compatible PC and the other side connects to an OCD (On-Chip Debug) port of the target system. This port may be JTAG, E-JTAG, OnCE, COP, BDM, or any of several other types of connections.


Иследование jtag_usb.dll от Macraigor Systems OCD Commander,
дало результать што Macraigor fast USB JTAG interface использует FT2232 чип .....

Очень заманчиво сделать клон usbDemon™.