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FTDI Comunication Problem - Sometimes FTDI cannot be found

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yujiahei:
Hallo,

i am working on a FPGA project and now facing a sporadic problem.

our project is about image capture device. we are using FTDI to transfer image data and command between device and host (computer). the ftdi is conneted to a on chip USB controller HUB. the FTDI is as self-powered mode configured. there are also some other chips connected with the on chip USB controller hub.

problem:
in the most time the system works good, but just sometimes, maybe in every 20-30 reconnecting, it can happen once, that the FTDI cannot be found in device manager (neither in USBview). the other chips which are also connected to the Hub are always ok, so I think the problem could by FTDI chip. So I mesured the critical pins value of FTDI like VBUS, WAKEUP, RESET and also the power supply for it. They are all correct.
From my side I think the reason could not be failed initialization of FTDI, because I didn't have to reboot the whole system but just reconnect it, then the FTDI appears again.
So I think, if it could be caused by unstable VBUS. But according to my mesurement there is no any glitch by VBUS when the problem happens.

Another weird point is that sometimes I can hear the correct beep, even when the issue happens. that means, we should have two chips registering in the device manager, and I can hear two times windows prompt tone when our device is being connected to pc, but I can not see the FTDI in device manager. And if when I focus on the USBView(a usb port tool), I am sure I can see somethings showing up on the port where the FTDI should be. But it disappers immeditaly.

at last I want to mention again, all these failures happen only randomly, around once in 20-30 reconnecting. most time it works fine.

I am looking forward for your help
Thanks a lot
YJH

FTDI Community:
Hello,

Which FTDI chip are using? have you got a schematic you can share? a USBView screenshot of the device would also be helpful. Also what kind of cable are you using to connect the FTDI device?

Best Regards

FTDI Community

yujiahei:
we are using FT601Q-B and the Cable is USB3.0 A to B. The relevante schematics and USBView screenshots are all in Attachments.

For your information, I also copied the USB info from usbview when the device works good. from the Timeview screenshots with name "Failed_1_UsbView.png" and "Failed_2_UsbView.png" you can find two failure situation.

by the way the driver is also the latest.

thanks

yujiahei:
sorry the attachments are too many. I have to upload them in two replies.
Thanks again.

yujiahei:
Update:

I tried to reset the ftdi from hardware side during running system, when the problem shows up. it can be fixed!
But I still don't understand why. Because if I don't reset it, but just reconnect it, I can also get the chip back in device manager.

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