Capturing Parallel Port Data

[M. Warner Losh]

In message: <BAY127-F2600E499F0FAE61D967201B3D40 at phx.gbl>
            "Mr CW" <mrcomputerwiz at hotmail.com> writes:
: Thank you for the pointers.  It sounds like reading data back from the 
: parallel port is not a common thing to do, although I thought parallel port 
: projects might have done this.  Then I realized that most PIC programmers, 
: parallel port displays, etc. usually only receive data, not send it back to 
: the computer...
: 
: I'm still looking into this, so any other suggestions are very welcome.

I've used parallel port connections in a few different products.

Usually, it is boring DIO stuff.  Not worth mentioning here, and we
use ppi.  However, sometimes we need data.  For that we write a
driver.  We connect the ACK line up as a 'data valid' line and then
read the data and/or control pins when it strobes inside the ISR.  We
use another line to 'ack' the data (which is backwards from how a
printer works).

Warner