Hi all, i have and product consists an USB port. For a reason, we have to modify the line from product to PC to another port (B) as attachment ( i make it in simple circuit). Even though the USB port B not connect or short circuit as i checked, but PC just recognize the USB A if i disconnect the DP and DN signal to USB B ( if i connect DP and DM to USB port B , then windows will pop up "USB malfunction , can't recognize"). Can someone educate me this case ?
PC not recognize usb after modification
- Thread starter hoangminh_cdt
- Start date
What makes you think you can hack up a cable and still have things work. The USB specification is very specific about this kind of thing. BTW you have probably now corrupted the Windows registry with your fooling around. Good luck cleaning it.
If you have not already done so at least get a copy of the USB specification and read the chapter on the physical layer interface and enumeration.
If you have not already done so at least get a copy of the USB specification and read the chapter on the physical layer interface and enumeration.
Relly thanks for your advise, i read the file but not understand clearly how it didn't if i split the line to the open port. Can you explain more
upand_at_them
- Joined May 15, 2010
- 940
A USB port goes either to a USB hub or to a *single* USB device. Two devices cannot share the same port. I suggest you read "USB Complete" by Jan Axelson for more information.
Welcome to AAC.
It would be very helpful if you could explain your reason instead of your failed solution. We may well be able to help solve the problem if you let us know what it is. As things stand all we know about your problem is that only a bad solution to a mysterious problem.
Hi Ya'akov, i have a test kit to test the usb port but there's a short term ultility on port A for manual testing, but there'll be a new fixture coming. so i modified the kit to make port B for readiness but not use for now, but after i modified, port A can not be recognized anymore
thanks for your recommendation, i will read it. but does it happen if i just use 1 port in a time ?
Something like this should do what you want.
I don't remember the exact details of how the host device examines the physical connection to the peripheral device and draws conclusions about the electrical properties. After completing that examination, it engages in the enumeration process where it exchanges information with the device about its capabilities. This process has stringent requirements on the format and content of the replies. Errors in this process result in Windows aborting the enumeration process without cleaning up changes it has made to the registry. N.B. This was Windows XP. Subsequent versions of Windows may now do a better job of error recovery, but maybe not.
I second getting a copy of Jan Axelson's book, it was most helpful to me in developing a USB device. You should still have the USB specifications since that is the ultimate arbiter.
