Can't connect to Zybo Z7-10 over USB, red LED no longer lights up when powered

[aytli]

I can no longer connect to my Zybo Z7-10. About an hour ago I tried to load a project on Vivado SDK, and it wasn't able to connect to the board. I restarted SDK, power cycled the board a few times, reconnected the usb cable, and also restarted my computer, and it still wasn't able to connect. I then tried using the hardware manager in Vivado to auto connect to it, and it didn't work. I've tried powering it with both the usb cable and a 5V wall adapter. I've tested the wall adapter and it's working fine.

After I gave up on connecting to it, I tried to run the demo project by switching the programming jumper to the QPSI position. The demo project didn't run, but I noticed that the red LED (PGOOD) was a little dimmer. Every time I powered up the board I can very clearly see that the red LED was getting weaker and weaker. As I'm writing this post, the LED is pretty much off (I can barely see a faint glow when I cup my hands over it). The LED is not entirely dead, when I use my multimeter to test continuity, the LED blinks briefly when I probe it. I didn't see or smell any smoke, and none of the large components felt warm when I powered up the board. I don't see any burn marks or cold joints on the board. I've probed the 5V rail, it is getting power from the wall adapter and it isn't shorted to ground.

This board was working fine an hour ago. The last project I compiled was an HDMI processor with a sink and source.

Did I accidentally burn my board? This board is just over 3 months old, is it covered by some kind of warranty?

EDIT: Probing that red LED gives me 3.3V on one end and about 1.7V on the other.

[jpeyron]

Hi @aytli,

We do have a RMA process but first we would like you to check some voltages using a DMM. Please check C222, C223, C229, C233, C237,and C240. Have you tried different usb cable or used a different Computer. Please download Adept 2 and see if Adept 2 can see the Zybo-Z7-10.

thank you,

Jon

[aytli]

Hi @jpeyron

I've probed those components and got the following voltages:

C222 - 5V across, I'm assuming this is the 0805 part. There's a smaller 0603 part beside it that measures 8V on one end and 3V on the other.
C223 - 3.3V
C229 - 3.3V
C233 - 1.8V
C237 - 5V
C240 - 1.8V

I have tried a different cable, which doesn't work. We don't have another computer with Vivado installed.

Adept 2 is able to see the board, and my computer does actually think that a device is connected. When I start the hardware server in Vivado, I get the following error message:

open_hw_target
INFO: [Labtoolstcl 44-466] Opening hw_target localhost:3121/xilinx_tcf/Digilent/210351A6AF38A
ERROR: [Labtools 27-2269] No devices detected on target localhost:3121/xilinx_tcf/Digilent/210351A6AF38A.
Check cable connectivity and that the target board is powered up then
use the disconnect_hw_server and connect_hw_server to re-register this hardware target.
ERROR: [Common 17-39] 'open_hw_target' failed due to earlier errors.

 

[jpeyron]

Hi @aytli,

I have sent you a PM about the next step for this issue.

thank you,

Jon

[cfowler]

On 1/4/2018 at 6:14 PM, aytli said:

I can no longer connect to my Zybo Z7-10. About an hour ago I tried to load a project on Vivado SDK, and it wasn't able to connect to the board. I restarted SDK, power cycled the board a few times, reconnected the usb cable, and also restarted my computer, and it still wasn't able to connect. I then tried using the hardware manager in Vivado to auto connect to it, and it didn't work. I've tried powering it with both the usb cable and a 5V wall adapter. I've tested the wall adapter and it's working fine.

After I gave up on connecting to it, I tried to run the demo project by switching the programming jumper to the QPSI position. The demo project didn't run, but I noticed that the red LED (PGOOD) was a little dimmer. Every time I powered up the board I can very clearly see that the red LED was getting weaker and weaker. As I'm writing this post, the LED is pretty much off (I can barely see a faint glow when I cup my hands over it). The LED is not entirely dead, when I use my multimeter to test continuity, the LED blinks briefly when I probe it. I didn't see or smell any smoke, and none of the large components felt warm when I powered up the board. I don't see any burn marks or cold joints on the board. I've probed the 5V rail, it is getting power from the wall adapter and it isn't shorted to ground.

This board was working fine an hour ago. The last project I compiled was an HDMI processor with a sink and source.

Did I accidentally burn my board? This board is just over 3 months old, is it covered by some kind of warranty?

EDIT: Probing that red LED gives me 3.3V on one end and about 1.7V on the other.

I am experiencing this exact failure mode, but on the 7020 version.  I built the HDMI example project which curiously features an HDMI source and sink and then made a FSBL and flashed a boot image to QSPI.  I had this running on a monitor before switching over to another task.  After while I went to turn off the board with the switch, but the board remained ON and I had to unplug the HDMI, USB, and 5V adapter to turn it off.  Now I only get a dim red "PGOOD" led that turns on and off with the board.

Board Voltages: 

• R293 to GND = 3.275 (VDC)
• R300 to GND = 0.997
• R305 to GND = 1.341
• R309 to GND = 1.806
• C222 to GND = 5.23

[cfowler]

Using Adept, the Zybo-Z7 only shows the a 7020 FPGA device, but no Arm CPUs or DAP.

Vivado only comes back with no devices detected on target and to check cables, target board power, etc... 

[JColvin]

Hi @cfowler,

I apologize for the delay. The values you provided are fairly reasonable; the main thing we look for usually is if one of them is drastically off or shorted, though I will check those values on my own Zybo Z7-20 that I have with me at home.

My understanding from what I have been told though is that it is possible to back-power the Zybo Z7 through HDMI (of which the power line is connected to the PS and not the PL) which seems like it could have happened here as well. I know it sounds odd, but I have also seen a 900 LED display be accidentally powered through a microcontroller which was powered through a laptops USB port (the LED display was normally powered by a 5V 20A external supply).

I am finding out what possible paths to recovery might be available.

Thanks,
JColvin

[cfowler]

1 hour ago, JColvin said:

Hi @cfowler,

I apologize for the delay. The values you provided are fairly reasonable; the main thing we look for usually is if one of them is drastically off or shorted, though I will check those values on my own Zybo Z7-20 that I have with me at home.

My understanding from what I have been told though is that it is possible to back-power the Zybo Z7 through HDMI (of which the power line is connected to the PS and not the PL) which seems like it could have happened here as well. I know it sounds odd, but I have also seen a 900 LED display be accidentally powered through a microcontroller which was powered through a laptops USB port (the LED display was normally powered by a 5V 20A external supply).

I am finding out what possible paths to recovery might be available.

Thanks,
JColvin

I completely understand back-powering.  I have been working on a custom Zynq 7030 board where the UART connection causes the platform cable to think VREF is satisfied.

Has there been more investigation as to the source of the back-powering and any mitigation other than disconnecting the HDMI connections before powering the board off and connecting them after its on?  I notice R134 connects VCC5V0 to HDMI_TX_5V0 and there are several components that deal with the HDMI signals before they are fed into the PL.  This is certainly an odd one.

[cfowler]

Hello @JColvin,

Is there any recovery method?

[Bianca]

Hi @cfowler,

Normally, Adept is not build to see the ZYNQ. The fact that it showed the FPGA part, still, shows like something is working. Please make sure that when you try to see the target on Vivado, Adept is closed otherwise Vivado would not recognize the device. 

If with Adept closed, Vivado still doesn't recognize the target, please check, if in device manager you have the device enumerated when you connect and turn on the board. It should appear as Serial Converter, if it doesn't show up at all or enumerates as unknown device or in some other way, please let me know. If it shows as unknown device, I am also interested in the Hardware ID in the Properties -> Details tab. 

When you say, you are "ONLY left with a dim led that turns on and off with the board" you say that the light is dim compared to how you remember it before the event but otherwise it works well like turning on when you switch the board on, or that is flashing and resets the board?

The values provided on the measurements above, show that the power supplies are working and they provide the desired voltages. 

Please also give me the serial number of your Zybo, you can find it on the bottom side or on the box. 

Regards,

Bianca

[cfowler]

2 hours ago, Bianca said:

Hi @cfowler,

Normally, Adept is not build to see the ZYNQ. The fact that it showed the FPGA part, still, shows like something is working. Please make sure that when you try to see the target on Vivado, Adept is closed otherwise Vivado would not recognize the device.

Hello, @Bianca.  I specifically installed Adept because of the suggestion above.  It was not installed prior to this issue occuring.

Quote

When you say, you are "ONLY left with a dim led that turns on and off with the board" you say that the light is dim compared to how you remember it before the event but otherwise it works well like turning on when you switch the board on, or that is flashing and resets the board?

It is definitely dimmer than one on a good board.  See the attached photos for a comparison between the PGOOD LED on a working and the bad board.

[asmi]

This is really odd issue. HDMI is only supposed to provide 50 mA of current on it's +5V rail, there is no way it will be enough to power the board. 

In the schematics, I noticed there is a fuse oddly enough marked R134. I would try desoldering it and replacing with Schottky diode to block reverse current from flowing into the board to see if that solved the issue.

[Bianca]

@cfowler, 

Please don't remove the fuse. I'll move the thread to private

@asmi,

You are right, this shouldn't have happened. I know we have issues with back powering through HDMI but it shouldn't be enough to keep the board working, or burn the fuse or other components. 

Bianca