January 2, 2021

EBAZ4205 Bitcoin miner board - Power

The advice on "xjtuecho's" github page is that this thing can be powered from one (or all?) of the Data1,2,3 connectors, or via the 6 pin molex (J4). However, if you intend to use J4, you must have a diode installed for D24 and most boards do not (mine doesn't).

What I did was to desolder D22 (which takes power from Data2) and transfer it to D24. This was a little bit of fussy soldering, but the diodes are big and mine seems to have taken the thermal abuse OK.

While the soldering iron was hot, I also installed the header for the serial port at J7.

Next I got a 6 inch "pigtail" of two conductors, soldered one end to the barrel jack that was so kindly provided with my board and the other end to J4. J4 is clearly marked. The three pins furthest from the board edge are all ground and the three pins nearest to the board edge are all 12 volts.

I dug a 12 volt, 1 amp "wall wart" out of my box of 12 volt warts, plugged it in and powered the board up!

Three green LED's come on immediately. One next to the ZYNQ chip (LED1), one next to the ethernet transformer, and one is on the "block" next to the RJ-45 connector. There is also a red LED on this block. It does not come on right away, but after a wait of 54 seconds it begins flashing at about 2 Hz.

That is it so far, but no smoke or fire, which is as much as we can ask without connecting the serial port.

More about power

I made some discoveries after having worked with these boards for over a year. One is that you can power the board with anything from 6-12 volts. You may even be able to power it with 5 volts. You will need to supply at least 400 mA, and perhaps more than that if you are using a lower voltage.

Just for the record, being excited by the possibilities offered by the above, I dug around and found a Sony branded 8.4 volt 400 ma "wall wart". When I connected this to the EBAZ, nothing working and the supply was pulled down to 4.5 volts. Apparently significantly more than 400 mA is require for the EBAZ at 8.4 volts.

Meanwhile back to my Nintendo "Game Cube" supply that is rated at 12 volts and 3.25 amps and works just fine.

The other pleasant discovery is that if you have an old PC power supply laying around, the power connector will mate with the "molex" on the EBAZ board. I chopped the connector off of a power supply I had laying around and then cut it up to get 3 usable connectors. Two of them have all 6 pins and one has 4 pins. So you can save yourself the trouble on removing the molex connetor on the EBAZ unless you really want to.

How much current?

As I begin to contemplate using these for various projects, I find myself wondering how big of a 12 volt supply I should provide.

So I took my fluke meter and measured the current draw as my board boots and runs U-boot and a standalone project I coded up.
I measure 150 mA.

Now this is with one core doing not much at all and nothing going on in the PL. Another piece of information might come from the Zedboard. This is a different chip (the XC7Z020), but it runs off of 12 volts. The Zedboard is designed for 60 watts (12 volts, 5 amps), but this allows for a significant load via the FMC expansion board. My Zedboard came with a 12 volt, 3 amp supply which has been adequate for everything I have done.

The Zybo uses the same Zynq chip, but runs from a 5 volt supply. Digilent recommends at least 2.5 amps (12.5 watts). This suggests that a 12 volt 2 amp supply might do just fine for the Ebaz (it would supply 24 watts).

On board power

The Ebaz has 4 on board regulators, each provided with a handy test point, as follows: The values given are what I measured. The values in parenthesis are the "nominal" voltage specified for that rail. Note that TP4 is incorrectly shown on the schematic as 1.9 volts. The datasheet indicates that this is 1.1 volts to run the internal logic on the PS and PL. The 1.5 volt rail is for DDR memory, the 1.8 is what they call an "aux" supply. On the Ebaz, all external interface signals (MIO and HR pins from the PL) run at 3.3 volts.
Feedback? Questions? Drop me a line!

Tom's Computer Info / [email protected]