EBAZ4205 Bitcoin miner board - JTAG

My interest is in using JTAG to read and more importantly to write the NAND flash. This could be a way of patching the NAND image (which I now do via U-Boot) or of installing a Kyu image into a NAND partition (which could also be done by way of U-Boot and tftp).

I have used the JTAG on the EBAZ board to inject JTAG images. To do this I use a homebrew USB to JTAG "dongle" made from a Pi Pico board. The board itself costs $4, so it is almost certainly the cheapest option available.

My pico runs "xvc-pico" where XVC is "Xilinx Virtual Cable".

• Github: xvc-pico: Xilinx Virtual Cable
• Github: pico-dirtyjtag
• Github: Dirty JTAG
• Github: Versaloon
• Urjtag.org (home page)
• CNX - nice article on blue pill and dirty jtag
• Using DirtyJTAG with UrJTAG
• EEVblog: JTAG is JTAG is JTAG
• Xilinx app note XAPP058
• Xapp058 local copy (23 pages, PDF)

I try "dnf install urjtag" and it works!

The above provides quite a group of options to investigate and sort out. From there, it is on to OpenOCD (or UrJTAG). Once we get something on the air, these links may be useful:

• My notes on openFPGAloader and xvcd-pico
• OpenOCD, JTAG, Segger, and hacking a router
• Extracting firmware using JTAG (flyswatter)
• JTAG interface, attackers perspective (24 page PDF)

He claims that UrJTAG is newer, simpler, and friendlier, yet I read elsewhere that UrJTAG is some of the oldest open source JTAG software. Who should we believe?