RE: Need help with parallel port input design-follow up question

Jeff,

To answer your question about the 10K resistor net (pack), no it does not go
to ground.

The pull up resistors work as such:
Think of the letter T, three ends.
End A connects to a wire terminal.
End B connects to parallel port.
End C connects to a resistor. The other end of the resistor is +5volts.


Refering to Dean's board, as you said you have it.
C1 is to clean up all the power coming in.
C2 is to clean any ripples that may occur out of the 7805.

>If so, am I right in assuming that VDD should be
>set at 5 volts and VSS as ground?

You should look at the data sheet. To answer you, yes.
Pin 7 goes to ground. Pin 14 goes +5V.

>Can I use the PC 5 volt supply?

Yes you can. But I'd still put a capacitor between the leads to filter the
power. You can get it from a the a power port, it comes out at +5 and
+12... I don't remember which wires... You can also get it from a game
port.

Don't quote me on this, but I think PS/2 port has 5+ as well. But then you
would give up a mouse, or KB.


Hope that helps,
Lloyd Leung