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I have a standard circuit, AtMega 328 or 168 with PD2 (INT0) D+ and PD3 D- with a 1k5 pull up on D- & 1M pull down on D+ fed with 3V3.

With minimal forever{ led on usbPoll led off} and debug level set to 2.

All I get is 24 ff: s i.e. reset condition. The pc is unable to enumerate (as though the AVR wasn't present but the 1k5 was).

I can see the PC's USB comms on pins PD2 & PD3 on an scope o.k.

Anybody give any tips on fault finding from here?

Many Thanks

Wrong fuses and so wrong clock?

Unlikely as the serial port works o.k. May be using at 3V instead of 5V for 12MHz but I'm assuming it can handle 12MHz at 3.3V, will test later.

I was following the Code and Life examples, with the above errors, so I started again using the examples with the download and it all works now even 3V @ 12MHz. May investigate debugging later. I'll learn the pseudo interrupts now.