Com port does not show up on Win 10 [SOLVED]


Tried plugging into hub, and also 2 different USB connections on laptop directly no sound from Windows, just power - and board has power LED and about 2 Hz pulsating LED. tinyprog 1.0.11
$ apio system --lsserial
Number of Serial devices found: 0
$ tinyprog -m
$ tinyprog -l

TinyProg CLI
Using device id 1d50:6130
No port was specified and no active bootloaders found.
Activate bootloader by pressing the reset button

NOW, if I press AND HOLD the Reset button, Windows shows in Device Manager:
Unknown USB Device (Device Descriptor Request Failed)

and when I let go of the Reset button, that Device Manager line under “Universal Serial Bus contolllers” goes away. At no time does any other serial port appear under Ports (COM & LPT) in Device Manager.

When I hold the Reset button down, the outermost LED goes to about 1/4 intensity.

I have 2 boards, they both show identical symptoms.

Help! All of my USB ports are USB 3.0 ports; could that be a problem?


This holds the FPGA in reset, it can’t do anything while in this state.

I’ve connected the board to both USB 3 and USB 2 ports without any issues, I don’t think that is the issue.

What CPU do you have in your laptop? Intel or AMD?


Intel Xeon E3 - 1200/1500 v5/6th Gen – Thinkpad P70


Is there anything else I can try? I am a geek, so can go pretty deep. Or should I return them? Should I sent them to you?

A clue, I think, is that when I press and hold the reset button for about 2 seconds, Win 10’s Device Manager under Universal Serial Bus controllers shows:

Unknown USB Device (Device Descriptor Request Failed)

Otherwise, nothing is shown in that section, nor is any ‘windows sound’ made when device is plugged in (which it does when recognizing a new device usually).

This suggests to me that, when the button is pressed and held for about 2 seconds, SOMETHING is happening, because otherwise Win 10 wouldn’t do what it does.



I’m looking into this as well…I’m trying to figure out which version of libusb you should install. If you have libusb installed, you can try the latest tinyprog beta I made for the people using MacOS. If you use that version with the —libusb command line flag you might get better results.


You’ll want the tinyprog version installed in this post: Can't create serial port


Good News, and Bad News. Good News: it works! with the old(er) software, too. New s/w also works.

the Bad News: I believe I have uncovered an electrical design issue with your USB implementation. It now works when I replaced the approximately 1 meter USB 2.0 certified cable with a 150-mm USB cable. Plugging that in immediately got Windows to say it was handling the driver, and all was good after that.

I suspect there is some Signal Integrity issue that needs to be handled; or maybe just asking people to use shorter USB cables. I suspect (wild guess) that there are reflections due to improper termination.

Thanks again for a super-duper board, and I know it takes a lot of effort to pull something like this off as a 1-man team. I appreciate your contribution.


Interesting, I use 2-meter cables all the time and haven’t had any issues. It could be that specific cable, or a combination of that cable and computer.

Glad to hear it’s working for you though! :smile:


I had the same issue with a 1m cable, and I consider this my “good” usb cable.