Objective Development Forums

Hi

The electronic supplier gave me incorrect zener diodes (3.0v ones). I tried without them but no go. Had no idea what was wrong, repeated everything and every tip I could find in triplicate. Even went back to supplier to reconfirm zeners, and they insisted it was correct.

Windows just failed device enumeration every single time.

The voltage supplied by the USB: 5.06V

D+: 0V in all cases.

Next D-:

So this was the before case (with 1k5 pullup to 5V):

With zeners: 2.45V
Without zeners: 4.1V

So with no access to other zeners, I guessed a stronger (is that correct?) pullup could maybe get that 2.45V up with the zeners.

Then I added another 1k5 pullup to 5V, and the resulting voltage on D- became 2.67V

Uploaded hid-mouse example to ATMega8 @ 16Mhz, plugged it in, and viola! Mouse detected, driver installed, and then it started moving across the screen (like I was hoping from day 1!)

So I guess it is really important to get that 'high' state at the correct voltage on D-.

One question though, would the extra pull up cause any other issues?

Cheers

leppie

yeah I to ran in to issues with zerners the 1n747a work fine but the 1N4148 do not. This is only true on some computers and using a hub makes both zerners work... So confusing! In this case both are 3.6 1/2 watt, have not found the aspect cause the issue in the data sheet yet.

Glad you got it to work V-USB is a nice project!

One question though, would the extra pull up cause any other issues?

I think your better off with the proper zener voltage If you target audience is more then one.

ulao wrote:yeah I to ran in to issues with zerners the 1n747a work fine but the 1N4148 do not.

Where are you using the 1N4148? They are not Zener diodes at all.

I believe your correct, they were sold as zener diodes. I also had seeed studios assemble a few broads and they used ss4148 where a zener 3.6 volt was called for. Thx for pointing that out.

ulao can i talk to you privately about seeed studio's kit service? send me a email at
frank at circleofcurrent dot com

I can't find the PM link on this site