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Zybo Z7, PGOOD led is not on, No devices detected on target in Vivado


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Hello,

I was working on Digilent Zybo Z7. While trying UART-to-USB cable on PMOD pins, I noticed that the board was hot and also smelly. Probably it was due to cheap cable or the fact that I connected 5V pin of cable to 3.3V PMOD pin. There was no immediate reaction after connecting the cable but I left the board on its own some time. After I noticed I closed the board from switch but the power led was on. I took the UART-to-USB cable out. There is no sign of burn in the components. Now, the power led does not get on. USB cable, which I was also for programming FPGA, is workin since I tried it with another board. I tried the programming cable with another computer port. I can see the connection in the Device Manager, communication points. When I click "Open Target" in the Vivado, it says "

 [Labtools 27-2269] No devices detected on target
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."

When I shutdown the board, Vivado says " [Labtoolstcl 44-513] HW Target shutdown. Closing target:". As far as I understand, the board is working to some extent but Vivado cannot reach FPGA. Device count is 0 in the Hardware Target Properties. My Vivado version is 2019.1. I also tried with the external 5V 3A adaptor with correct jumper configuration, but no improvement. Following suggestions in the

 I measured the mentioned capacitances.

C219, C220, C221, C222 are approximately 5V when powered with USB, approximately 5.3V when powered with external adaptor. C228 and C229 are 3.26V in both case. C237 is 1.33V, C240 is 1.78V in both case. Hopefully, I mesured correct capacitances, see image in the attachments. Currently, I cannot see any led "on" and cannot program FPGA.

 

Can you help me?

--Edit: Line in the image is irrelevant

WhatsApp Image 2021-04-02 at 15.44.25.jpeg

Edited by Serdar Unal
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HI @Serdar Unal,

It looks like you choose measured the capacitors based on what you highlighted and their values all seem reasonable indicating that those specific connections on the power regulator are receiving and producing power, though I'm not sure why the power good LED (LD13) is not turning on.

Do you have the Zybo Z7-10 or the Zybo Z7-20 (no heatsink vs heatsink, respectively)?

Connecting a 5V supply to a 3.3V supply is definitely a point of concern. Was this directly on the power supply pin (pins 6 and 12) on the Pmod host ports or one of the 3.3V IO pins? Which Pmod port specifically was this on? My concern is if the 5V side was enabled, that current may have flowed into the FPGA at a higher rate than it could handle, causing something to overheat and burn internally within the FPGA.

Are you able to detect the Zybo Z7 on your OS? On Windows machine, it would show up in the Device Manager Under Universal Serial Bus controllers as USB Serial Convert A and USB Serial Converter B, both with Bus reported device descriptions in their details tab of their Properties of "Digilent Adept USB Device".

Thanks,
JColvin

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Hello,

I have Zybo Z7-20, it has heat sink. I connected it to power supply pin of the pmod port. But I could not remember exactly whether it was JB or JC. I measured all 3.3V pins of all PMOD banks (JA, JB, JC, JD, JE, JF), they all give approximately 3.3V when the board is powered. Yes, probably 5V side was enabled, I can measure 5V when I connect USB end of UART-USB cable to computer and leave other end open. There seems no problem in the computer side.

Yes I can see both USB Serial Convert A and USB Serial Convert B with Digilent Adept USB Device descriptions on Windows

Thanks,

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By the way, when I measure the voltage across pgood led (LED13) I get different values. Sometimes 1.3, sometimes 1.7, 1.8, 2, 2.20 etc. But these are high values, I should be able to see led is glowing, do not I? While I play with multimeter I can see very tiny glow, probably current goes through multimeter. So, I conclude that Led is not completely broken. However, DONE led is much more stable, I get always 282 mV.

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Posted (edited)

I noticed something seemingly relevant. Measuring D17 with DMM, in diodes and continuity mode, results in beep. It displays approximately 240 mV in the screen. Does that mean that I should replace the diode? When I touch to the diode with DMM as described above, pgood led turns on interestingly.

Ekran Alıntısı.PNG

Edited by Serdar Unal
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Hi @Serdar Unal,

Okay; I had asked about which Pmod port had been used since a number of the Pmod ports do not have current limiting resistors on the I/O lines, which could have then easily permanently damaged the FPGA pins. But that does not appear to be the case here.

The diode might need replacing; personally I want to ensure that the Zybo Z7 is properly being detected by and programmed by Vivado, which does not appear to be the case. The pgood LED will only turn on if the 3.3 V supply is working (this seems to be the case) and if PG_ALL is working. In principle, it should be functional because it monitors the output voltage on Channel 1, which was successfully measured on C228 & C229, and the channel 1 is only enabled if channel 4 (measured C240) is working, so in theory the power regulator is functional.

The board itself is successfully detected by the Windows Device Manager, so that's a good indicator. I didn't explicitly ask you before, but I presume the Zybo Z7-20 is also detected correctly by the Digilent Adept software (https://reference.digilentinc.com/reference/software/adept/start); this is the software and drivers that Vivado uses to detect and program the Digilent boards (based on my understanding) so it would be a good litmus test to see if Vivado should be detecting the board.

You mentioned for the diode D17 that you got a beep during it's continuity test. Was that in only one orientation of the DMM probes or in both orientations? If it's both orientations, then replacing the diode could fix the pgood LED, but that most likely will not fix the "programmability" of the board.

Thanks,
JColvin

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Hi,

Thanks for your answer. I showed the Zybo Z7 to someone knowledgeable about boards. He measured different places and could not find the reason. He said that probably I damaged the FPGA itself which is not a good sign. Beeping was only in one orientation. Yes, probably I gave voltage to gate of the transistor which is responsible for PGOOD led, this is why it turned on. I though it was relevant in the beginning, but I later realized that it is not relavant to our problem. Thanks for your help.

-- By the way, I also used one of the normal I/O ports of PMOD, in addition to power&ground ports of PMOD. Maybe I damaged as you suggested

Thanks,

Serdar

Edited by Serdar Unal
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Hi @Serdar Unal,

Yes, unfortunately it sounds like the FPGA was damaged though the EEPROM is still intact which would be why it is successfully detected by the Windows OS.

If you purchased the board through Digilent directly, you might be able to request an RMA depending on when you purchased it, though because there isn't really a firm way of definitively proving that this was a manufacturing error, I don't know if the Digilent Sales team will approve it. If you purchased the board from a distributor, you will need to contact them about their RMA policies.

Let me know if you have any questions about this.

Thanks,
JColvin

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