AVRUSB on Arduino Diecimila?

[BrianC]

I built a simple shield/daughter card, with 3.6v 1w zener diodes and what I believe are the appropriate resistors (2.2K pullup (to 5v) on D-, 1M pulldown on D+, and 68 ohms between the D+- lines and the Arduino ports 2 & 4), but it didn't work. I enabled DEBUG_LEVEL=2, and I see a continuous stream of "ff:", which appears to mean that the bus is constantly being reset.

Vista reports "USB device not recognized"

I'm running Vista on a Dell XPS1730, with the Arduino 012 codebase/compiler.

Has anyone seen this behavior, or have any suggestions on how to fix this?

Here is part of the debug log:

00:Cá01:
02:
ff:
03:
23: c3 00 ff 07 00 cd db
02:
ff:
02:
ff:
(lots more 02:, ff:)
02:
1d: 80 06 00 01 00 00 40 00
20: 4b 12 01 10 01 00 00 00 08 11 77
ff:
02:
20: c3 c0 16 df 05 00 01 01 02 ca 9b
ff:
02:
20: 4b 00 01 3f 8f
ff:
02:
(lots more 02:, ff:)
ff:
02:
1d: 00 05 02 00 00 00 00 00
20: 4b 00 00
02:
(lots more 02:, ff:)
ff:
02:
1d: 80 06 00 01 00 00 40 00
20: 4b 12 01 10 01 00 00 00 08 11 77
ff:
02:
20: c3 c0 16 df 05 00 01 01 02 ca 9b
ff:
02:
20: 4b 00 01 3f 8f

[christian]

2.2 kOhm may be too high. Did you check the voltage levels? Also make sure that your zener diodes are really low power types. You do use zeners, do you?

[BrianC]

The problem wasn't the resistor, but the zener. Initially, all I could find at the local parts stores was 1 watt zeners, but eventually I found 500mW 1N747A. With this new zener, it worked.

Looking at the datasheets I see that the electrical characteristics differ between the 1W and 500mW zeners, which is very counter-intuitive - just like others had reported, and whose advice I ignored. My bad.

Thanks for your help.