Zybo Z7-10 short circuit between v3.3 and gnd from raspberry pi

[matthieu]

Hello everyone and nice to meet you

I accidentally plugged in the PMOD JE and JD to the pins 19 to 30 and 1 to 12 of my raspberry pi without thinking about it. 
Since then the Zybo power led won't light up and won't connect via usb, so i suspect a short-circuit happened on the zybo between JE(6) and the ground from pin 30 of the raspi  (although the raspi seems unaffected). 

Is there a method to test whether the card is dead or if it can be repaired?

I am not familliar enough with it to determine if a fuse or a resistor burned, or if a converter/FPGA/other died.

Thanks a lot for your time and answers,

Best Regards,

[JColvin]

Hi @matthieu,

If the board is not being detected and the power LED is not turning on, that is not a good start.

The power LED only turns on when the PG_ALL (power good all) signal from the on board regulator (page 14 of the Zybo Z7 schematic, https://files.digilent.com/resources/programmable-logic/zybo-z7/zybo-z7-d1-sch.pdf) is active. The PG_ALL signal then cascades and acts as the enable signal for a lot of other systems on the board including the Zynq SoC, the analog voltage supply, HDMI, etc.

You can check the voltage on a number of the larger capacitors around the regulator (IC25; it's on the underside of the board with the 4 inductors surrounding it) such as the 47 uF capacitors on each of the main output rails (C228 for 3.3 V, C232 for 1.0 V, C237 for 1.35 V, C240 for 1.8 V) and C222 for the 5.0 V source input. If you do end up finding any of the voltage rails non functional, some more debugging can be done to figure out if it is one (or more) capacitors that got fried or if it is the regulator. Replacing the potential multiple failure points will not be an easy endeavor though.
I don't have a Zybo Z7 with me at my home office so I can take a higher resolution picture showing the locations of the components of interest unfortunately.

However, if the FPGA bank 34 that JD was attached to (and received 5.0 V into its pins that do not have any series resistors on) was damaged beyond just the directly affected pins, there will not be anything you can do to recover that (as far as I know).

Thanks,
JColvin

[matthieu]

Thanks a lot for your fast and detailled answer,
I'll check this with my colleagues when we have some time (we bought a replacement one in the meantime so it's not as urgent anymore).
I hope that we'll be able to fix it nontheless...

Thanks a lot and wish you all best, 

Matthieu