Arduino to touchpad

Has anyone had success connecting an Arduino to a synaptics touchpad? I have a pad from an older Dell laptop. It is supposedly using the PS/2 protocol, and I hope to use the ps/2 code in the playground for reading it. I have the pad wired up correctly (I think) and I have a scope hooked up to (what I think is) the clock pin. When I apply power, the touchpad is sending sequence of pulses over the clock pin, but they are between 5V and about 4.5 volts. It never drops low enough to be read by the Arduino digital input. If anyone has any experience figuring out the way to do this I would love to hear it! Thanks! Josh

Connect it to a computer's PS/2 port to double check. :)

Not sure why it would pulse LOW at 4.5v. :-?

Thanks Cheater! Excellent suggestion.

Of course it does not work when connected to the PS/2 port either.

I have searched the internets for hints on hooking this particular model (TM41PDD219-1) up and have found nothing. I did find excellent references for other models, but this one does not appear to be documented. If anyone is in need of Synaptics literature it is available on their web site (

I suppose I will keep hunting...