I have a circuit in witch I have used USBUF02W6, and every time I plug USB (circuit is usb powered) windows detect my usb device as unknown device, but if I take power from a battery and then after some seconds I plug usb my device is correctly recognized.
I have tryed to disable internal transceever at startup and then enable it again but noting, on D- I have 0V and on D+ >2.5V with or without ransceerever enabled. The usb schematic is the same of evaluation board "http://www.atmel.com/dyn/resources/prod_documents/doc6195.pdf" page 24.
I configured every registry after power on periferal.

Can someone tell me why? Is a software problem? Someone have an example of disabling usb at startup and enable it after registry initialization?

Best regards Gian

Hi Gian

The fact that the USBUF02W6 has a pull up resistor makes debugging with it difficult (if not impossible). When applying power to the board via USB, the USB host will immediately try to enumerate. This will fail if the USB SW on the board is not immediately running.

Take a look at the Olimex SAM7X board as reference for a circuit which allows the SW to control the start of USB enumeration once it is ready:
http://www.olimex.com/dev/sam7-ex256.html

Regards

Mark

www.uTasker.com