Hi all,
I have been asked by a colleague to help him out with a parallel port
problem.
the problem is that they have an application that controls an external
device via the parallel port.
communication is implemented by reading and writing bytes on the parallel
port via port io functions on a specific port.
now they want to be able to run the program on a pc that has no real io
port, so they want to use a USB to parallel convertor.
the old app doesn’t work anymore, so he asked me what I could do about it.
since we have the app sources, I was thinking about simply opening a handle
to the virtual comm port, and then reading and writing on the handle, though
I can forsee some timing problems, and I don’t know if the lines retain the
value of the last byte that was sent (it is a requirement).
my question: does anyone perhaps have an alternative approach, or some tips?
I have searched around, but could not find any useful information yet.
most information is about port io, which is exactly what I cannot use in
this case.
–
Kind regards,
Bruno van Dooren
xxxxx@hotmail.com
Remove only “_nos_pam”
Bruno van Dooren wrote:
I have been asked by a colleague to help him out with a parallel port
problem.
the problem is that they have an application that controls an external
device via the parallel port.
communication is implemented by reading and writing bytes on the parallel
port via port io functions on a specific port.
now they want to be able to run the program on a pc that has no real io
port, so they want to use a USB to parallel convertor.
the old app doesn’t work anymore, so he asked me what I could do about it.
since we have the app sources, I was thinking about simply opening a handle
to the virtual comm port, and then reading and writing on the handle, though
I can forsee some timing problems, and I don’t know if the lines retain the
value of the last byte that was sent (it is a requirement).
my question: does anyone perhaps have an alternative approach, or some tips?
I have searched around, but could not find any useful information yet.
most information is about port io, which is exactly what I cannot use in
this case.
The USB-to-parallel connectors USB Print Class spec; they are designed
for shipping bulk data to real printers. They aren’t designed for
low-level tweak-the-wires access. There’s no guarantee that reads and
writes actually map to reads and writes to the parallel pins in any
sensible way. Writes probably works as you expect, but reading is
problematic.
Is this a laptop? There are some good PCMCIA parallel port cards. You
may also be able to get a PCI parallel port card.
Alternatively, there are a couple of companies who sell very simple USB
devices with terminal blocks on the other end, designed specifically for
your kind of tweaking. Here’s one:
http://www.accesio.com/go.cgi?p=../digital/usb-dio-32.html
–
Tim Roberts, xxxxx@probo.com
Providenza & Boekelheide, Inc.