"Unknown Device" detected in WinXP

General discussions about V-USB, our firmware-only implementation of a low speed USB device on Atmel's AVR microcontrollers
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"Unknown Device" detected in WinXP

Post by mw » Sun Feb 04, 2007 12:23 am


I'm trying to get ANY of the USB projects working, so far I've tried PowerSwitch, SNES Gamepad, and USB-LCD and I can't get windows to load the right driver for any of them. I get an "Unkonown Device" warning saying that it is malfunctioning. I have tried using the power line of the usb cable as well as an external source, I've used 3.6v zeners on the data lines, and I also tried using an LM317 to get the right voltage, but nothing seems to be working. I have the following uC's on hand which I can use to try different projects:


Can anybody help me out here? Thanks,


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Post by Grendel » Sun Feb 04, 2007 1:22 am

In windows an unknown, malf device means that the speed resitor is active but the device is not reacting or sending garbage. Invalid usbconfig.h entries or fuse/config bits set wrong are a good source for this error (assuming the hardware is wired right.)

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Post by christian » Sun Feb 04, 2007 3:02 pm

My first guess would be that you have not programmed the fuse bits correctly and the AVR is running on the internal RC oscillator. As Grendel already pointed out, an unknown or malfunctioning device usually indicates that the AVR is not sending any useful data at all.


Post by mw » Sun Feb 04, 2007 4:59 pm

I got USB-LCD working by playing with the values of the resistors for the LM317. I guess my laptop is picky with the voltages. I'll proceed from here using this hardware setup. Thanks for your help.

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