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PICList Thread
'PC Parallel Port'
1996\07\04@082019 by John B C Walker

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Dear All,

Initially this may not seem PIC oriented, but it is. I'm trying to get a
PC running Windows 3.1 to talk to a PIC through the PC parallel port, but
I've come across a problem:

I'm using VB4.0 with hardware accesses through DLLs written in Turbo C.
No problems with that part. Writing and reading to the parallel port is
also simple and error-free. But I want to implement handshaking, so I
need to strobe some of the other lines on the port. This involves
accessing the status register(offset 01h) and the control register(offset
02h). I'm using the STR line to indicate data_valid and the /ACK line to
indicate busy from the PIC. Once I write and read the other registers, it
is no longer possible to write to the data register, i.e. the data lines.
This only happens in Windows (3.1/95) not in MS-DOS. Because of this, I
suspect there is a conflict with a printer driver, and it is therefore
not possible to directly access the parallel port while running Windows.

Does anybody have any experience on this topic? Is there a solution?

Thanks very much.

J.W.

-----------------------------------------------------------------
       Johnnie Walker
       MSc Digital Systems Engineering
       Heriot-Watt University
       email: spam_OUTceejbcwTakeThisOuTspamcee.hw.ac.uk
              .....ceejbwKILLspamspam@spam@pp.hw.ac.uk
              ceejbwspamKILLspamtorduff.hw.ac.uk
       www: http://www.cee.hw.ac.uk/~ceejbcw
       tel: (0131) 343 2864
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1996\07\04@083302 by Wolfram Liebchen

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John B C Walker wrote:
> .....
> This only happens in Windows (3.1/95) not in MS-DOS. Because of this, I
> suspect there is a conflict with a printer driver, and it is therefore
> not possible to directly access the parallel port while running Windows.
>
> J.W.

John,

if you use Windows 95, you could try to dectivate the LPT port in the
device manager. I saw some network pocket adapters (connected via
printer port) requiring this measure.

Wolfram

--

+-----------------------------------------------+
! Wolfram Liebchen, .....liebchenKILLspamspam.....ipserv.ffo.fgan.de !
!        Forschungsinstitut fuer Optik          !
+-----------------------------------------------+

1996\07\04@135158 by Antti Lukats

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At 13:20 04.07.96 +0100, you wrote:
{Quote hidden}

Hi J. W.

There is a very simple way to fake Windows 95 printer driver if that
is the problem:
add 0x8000 hex to the port address!
it will access the port in question but will completly bypass
_any_ virtual drivers!
its real simple and it does work in 3.11-95
Dont try it on NT!

The problem however may not lie there, if you have bi-directional
port you may set it to be input, and than you want see any data
written to the port.

cheers antti

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