Patrick J wrote:
>
> From: "Roman Black"
> > If you connect to the INPUTS in the par port,
> > these normally have a fairly strong pullup
> > resistor attached and you will need a very
> > low series resistor, any values over 180 ohms
> > will fail to pull the par port inputs low
> > enough, 120 ohms is a good value.
> >
> > For the par port OUTPUTS just use a 1k or 2k2
> > resistor between the par port output and your
> > logic chip input.
>
> I had 1k resistors between the port and the pic and got
> random data. After changing to 470 ohms i got a reliable
> data transmission. Maybe you need 470 to be able to
> drive the cap. in some ports.
> The strange thing was that that i could SEND reliable,
> but when reciving data on the PC it was random.
>
> Now my test program has sent more than 10 mil data bytes
> and zero error bytes in return. And no timeouts.


Patrick, it's exactly what I mentioned above,
when receiving data on the PC you need to pull down
the logic level against the pull-up resistors in the
PC par port. Use 120 ohm resistors!! It may work now
with 470 ohms, but when moved to other PCs you will
get problems. Trust me! :o)
-Roman

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