Parallel port:

Are you just polling the parallel port in a tight Delphi loop? What does
that code look like?

Image display:

I am guessing that you are just drawing the pixels one-by-one on the PC.
That is far from efficient. You need to build up an in-memory image, called
a DIB, then blast the entire image to the screen in one operation. Much
faster!

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

----- Original Message -----
From: David Pearson (SKYTRONICS) <skytron@HOME.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Wednesday, December 27, 2000 12:17 AM
Subject: [PIC]: PIC data via PC parallel port to screen


> Hi,
>         To all the PC programming experts a couple of questions.
> I'm transferring data from a CCD image sensor for display on a PC via the
> parallel port.  Works fine, 8 bit gray scale. 400 x 280 pixels.  I'm using
a
> F877 to transfer data to the PC using the parallel port in Bi-directional
> mode.  On the PC end, I'm using Delphi 5 with my own Assembly Portin,
> Portout, Porttest routines.  Plotting pixels using the Plotxy functions.
>
> The problem, it's very slow.  It takes ~12 seconds to plot a frame on a
> Pentium 120.  From what I've read, the maximum toggle rate I can expect on
> the parallel port is 500 nsec to 2 usecs, depending on what you read.
Even
> so, I'm seeing times between setting a bit on the parallel port by the
F877
> to the time the PC recognizes the signal of about 15 usecs.  Also,  the
> plotting routine itself is slow, about 6 seconds to plot the 400 X 280
frame
> when plotting a test grayscale pattern, no port IO, just incrementing the
> plot value.
>
> Does anyone have any ideas on how to speed things up?  I need a Windoze
> 95/98 environment using either Delphi or VB.
> Any ideas on how to speed up the data transfer?  Faster portIO?  Faster
> Plotting in Delphi?
> It seems crazy to me that my $5.00 PIC has to wait for a 120 MHz machine
to
> do data transfers.  Is the Windoze environment that inefficient?
>
> Any ideas and help is appreciated and may be useful to other group
members.
>
> --
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>

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