Digilent CMOD A7 Disconnects and/or does not Program

[Christian Klein]

I've seen similar issues in the forum, but no real solution.

I have 5 CMOD A7 boards and only 2 of  them behave properly.

The other 3 do not accept a program and sometimes disconnect.

I get the following errors;
ERROR: [Labtools 27-3165] End of startup status: LOW
ERROR: [Common 17-39] 'program_hw_devices' failed due to earlier errors.

I have tried:

- many different USB cables

- Different ports on the PC

- Powered USB hubs

- Vivado Lab 2017.2 and 2018.1

- 2 different bitstream files

 

The boards that work, always works. No matter the cable or USB ports.

Anything else I should try?

 

 

 

 

[jpeyron]

Hi @fentonc,

Here is the forum thread that discussed the USB cable issue that is with the Cmod A7.  Are the usb cable connections loose on the cmod a7 devices that are not working. Also please attach a screen shot of the text in adept when it connects and then disappears.

thank you,

Jon

[fentonc]

Yes, I do see the same behavior with and without the USB hub. I only tried adept 2 on the windows 10 laptop, and I see similar behavior (sometimes the board appears briefly, but then it goes away)

[jpeyron]

Hi @fentonc,

Do you see the same issues without using the usb hub? Please download Adept 2 here? Do you experience the same issues using Adept 2?

thank you,

Jon

[fentonc]

Ugh, this feels like a flakey hardware issue. What do you use besides vivado to configure it?

[zygot]

Yes this is an issue with the CMOD-A7. It is not an issue with cables ( even if Digilent would wish it to be so). It is an issue with the interface on the CMOD-A7 and a particular issue when Vivado hardware manager is opened ( for instance in trying to use the ILA feature ).

Some problems, even those that shouldn't be hard, take Digilent years to resolve. I've stopped trying to use Vivado ILA or the USB UART with the CMOD-A7 . I do use something other than Vivado to configure the CMOD-A7. I do connect a separate USB UART cable to 2 spare IO pins to have nice uninterrupted productive UART sessions with my FPGA application. 

This issue has been known for a few years now. It took me almost 3 years to get the Genesys2 documentation free from silly errors but I kept after them until someone actually looked into the problem. I suspect that this problem cannot be resolved retroactively for current customers.... but no one is paying me to figure out the exact nature of the problem.

[fentonc]

I've been experiencing this same issue with my Cmod A7-35T board, and I would love a solution to it. I've seen flaky behavior across multiple USB cables and 3 different computers (a windows and linux laptop, and a linux workstation). Typically I will plug in the device and it will disconnect after 15-20 seconds. On windows, the USB device rarely shows up again, whereas on the Linux workstation it seems to re-connect most of the time. If I'm quick, I was occasionally able to program the FPGA with a new bitfile before it disconnects on linux. I tried programming the flash, but it always dies a couple seconds into the 'erase' step.

My suspicion is some kind of hardware fault, but I'm not sure how to diagnose it further. Any suggestions would be welcome!

[xc6lx45]

Remembered one thing: You were using only a single PC, is that so? Try another one.

It may be that there are broken drivers somewhere in the Windows directory. Maybe the USB hardware is unreliable. A powered hub won't automatically fix it.

If a full install is too much work, use the LabToy.exe file and put the FTDI drivers into the same folder (or install them system-wide via FTDI's installer). Speaking of which, updating them to the latest version (8/2017!) might be worth a shot in any case.

 

 

[xc6lx45]

Hi,

if you want a 2nd opinion, you can try my labToy executable. It runs completely independent JTAG code.

Most likely, it'll fail the same. But if it happens to work reliably, the next question would be "why".

I suspect it's USB power related - you might give it a shot to supply the boards externally.