I have a VNA V2Plus 4 (latest build) that has been working well.  I now have an issue though when I plug the USB from my laptop, the screen starts flashing white.  I’ve got a Macbook pro with most recent software macOS V11.2.2.  Using vna qt, but at this point cannot connect to it.  When I do get it to recognize the device, when I try to connect, it comes back with file not found. 



I solved this once, after several reboots of the Mac.  But now this is happening continuously and cannot connect.  When the USB isn’t plugged in, it seems to be working fine. 



Any ideas?

Lynn, WA4FKX

It seems I have something weird with a driver.  When I plug it into a different port, it connects.  But when I go back to the original port, same issue again.  I’ve run into this with a USBasp programmer, but that took a non-standard driver. A little weird that it worked using a standard driver and I’m having this issue.  Can switch to a windows box, but sounds like that has it’s issues as well. 



If anyone has any suggestions, let me know. 



Lynn, WA4FKX



From: <NanoVNAV2@groups.io> on behalf of Lynn Mears <l.mears@comcast.net>
Reply-To: <NanoVNAV2@groups.io>
Date: Sunday, May 2, 2021 at 2:38 PM
To: <nanovnav2@groups.io>
Subject: [nanovnav2] VNA V2Plus 4 flashing screen



I have a VNA V2Plus 4 (latest build) that has been working well. I now have an issue though when I plug the USB from my laptop, the screen starts flashing white. I’ve got a Macbook pro with most recent software macOS V11.2.2. Using vna qt, but at this point cannot connect to it. When I do get it to recognize the device, when I try to connect, it comes back with file not found.



I solved this once, after several reboots of the Mac. But now this is happening continuously and cannot connect. When the USB isn’t plugged in, it seems to be working fine.



Any ideas?

Lynn, WA4FKX

Or bad cable, or USB port does not supply the current required for operation

It could be a bad cable but unlikely. I used the port and all cables without any issue multiple times. I have a docking station with two external monitors connected. When the laptop goes to sleep, and then I wake it up, it often does not recognize both monitors and sometimes locks up. This happened and I had to do a hard reset on the laptop and after that is when I started to have issues connecting to the vna. So I’m thinking it’s more of a driver or OS issue. But could be wrong.

I got perturbed with Microsoft over taking control of my pc away from me and switched to a Mac. Over time I’ve found Macs have their issues too. No simple solutions these days!

Lynn, WA4FKX

> On May 2, 2021, at 4:25 PM, DiSlord <dislordlive@gmail.com> wrote:
>
> Or bad cable, or USB port does not supply the current required for operation
>

I experienced the same behavior with two V2plus4, resolved it by simply using different USB cable.

Simon, DC0SK

Yes, although I responded to DiSlord it was unlikely you are both correct. The bad actor was actually the cable that came with the VNA. Yesterday it wasn’t working in any configuration, but I moved it and it came to life. Turns out any flexing of the usb cable that came with the unit caused the problem. When I hooked the unit up to a new port previously it took that flexure out. Should have given the cables a more rigorous workout when DiSlord originally said something! I haven’t yet but that cable will soon be in two pieces. So I bow to the DiSlord!

Lynn, WA4FKX.

> On May 5, 2021, at 7:06 AM, dc0sk via groups.io <dc0sk=secure.mailbox.org@groups.io> wrote:
>
> I experienced the same behavior with two V2plus4, resolved it by simply using different USB cable.
>
> Simon, DC0SK
>

Hi there,
My NanoVNA V2 Plus4 just arrived. Few minutes ago, I tried to connect it to the PC, and I got exactly the same problem as Lynn: the NanoVNA LCD began to flicker (on white). First, I tried separately on a laptop, using the stock USB cable - and it worked; on my desktop PC, not.
After that, I found this message on the group and I changed the USB cable with a brand new one, and the problem is solved, now works !

However, I cannot explain this very interesting behaviour: the stock cable works on laptop, but not on the desktop. Hmmm.
I forgot to mention that on the desktop, I tried on the front USB ports (less power). However, in my situation, the NanoVNA is powered by its own battery (fully charged) - so I suppose that only the USB Rx/Tx signals matters. Or I am wrong ?

Thanks and all the best!

Had same issue. Tried multiple cables/powered hubs. What fixed it for me was simply using a USB port on the computer itself. My issue now is no COM port shows up with the unit connected and in firmware update mode. Device manager in Win10x64 refreshes but no COM port appears. Goal is to update the firmware.

maybe you have used a "charge only" cable ?!?

Am 25.03.2022 um 23:16 schrieb Kk6qms:

> Had same issue. Tried multiple cables/powered hubs. What fixed it for
> me was simply using a USB port on the computer itself. My issue now is
> no COM port shows up with the unit connected and in firmware update
> mode. Device manager in Win10x64 refreshes but no COM port appears.
> Goal is to update the firmware.
>

Negative. I have never seen a USB A to USB B cable that is charge only. I tried at least 3 different cables.
A reboot of PC with VNA connected and powered on allowed it to be recognized properly and I was able to update the firmware.
Thanks.