April 24, 2024

EBAZ4205 Bitcoin miner board - JTAG pins and cables

The Ebaz board has a 14 pin connector (J8) for JTAG. There are actually only 4 active signals on the Ebaz. One whole side of the connector (7 pins) are grounds.
On the other side, the 7 pins look like this:
pin 2 - 3.3 volts (Vcc)
pin 4 - TMS
pin 6 - TCK
pin  8 - TDO
pin 10 - TDI
pin 12 - n/c
pin 14 - n/c
I measure 3.33 volts on pin 2, which is there to tell the JTAG adapter what voltage levels it should use. I could be 5 volts (very unlikely these days) or even 2.5 or 1.8 volts, so don't assume anything in the general case.

On the Antminer S9, we have a 14 pin header with the same pins. However pin 14 is a jtag reset. This is as it should be, and it certainly is too bad that reset signals are not on this connector for the Ebaz boards.

Dirty JTAG pins

This is the pinout on the Blue Pill. I list the pins in numerical order, unlike the DirtyJTAG page.
PA7     TDI
PA6     TDO
PA5     TCK
PA4     TRST	(I skip this)
PA3     TMS
PA2     SRST	(I don't use this).
So, for the Ebaz, we can forget the last 2 pins, find a ground somewhere, and wire up 5 wires and be in business. When I wired up the cable for my XVC-PIO, I used 6 wires, providing two ground connections for good measure. I do the same here also (I provide two grounds).

Versaloon pins

The blue pill again, but these are the pins we use for Versaloon:
TDI --- GPIO B15
TDO --- GPIO B14
TCK --- GPIO B13
TMS --- GPIO B4

Feedback? Questions? Drop me a line!

Tom's Computer Info / [email protected]