I recently worked with Kyosti to update the EHCI Debug cable.
You can find an updated version of the cable here, under examples/debugdev_full_duplex.
There is a .PDF with a build spec based on the newer version of the FX2LP boards that are easily available from taobao or eBay. It should work with the old ones too. It is a slightly modified version of Kyosti’s original (excellent) spec that got me started.
The new cable/firmware complies with the 8-byte packet requirement of the EHCI Debug Device specification to avoid overrunning the EHCI Debug port buffers. Also in theory it should be faster (perhaps if you remove the 8-byte packetization) due to the use of GPIF streaming.
The EHCI Debug cable implements the CDC ACM spec - I didn’t modify that part at all, but in theory it should appear as a standard serial port under Windows. I’ve tested it with Linux and OS X and both support it natively through CDC ACM drivers and I believe a friend of mine tested it working as such.
Also EDK2 supports it for SourceLevelDebugPkg. That needs some minor patches as EDK2 hard-codes the USB endpoint numbers for Ajays - I may contribute back patches to read those from the descriptor at some point but it’s an easy modification to make manually.
Regards,
Chris.