> Subject: [PIC]: PIC data via PC parallel port to screen
> Date: Wed, 27 Dec 2000 00:17:47 -0500
> From: "David Pearson (SKYTRONICS)" <skytron@HOME.COM>
>
> 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.


1. "Is windows that inefficient" = YES
2. "any ideas and help" = May be difficult! :o)

I use the parallel port for data input all the time, not
having access to ICE and other expensive goodies I do it
the hard way by attaching most of my PIC projects into
the par port and this gives benefits over the ICE anyway
with the ability to chart waveforms and do sophisticated
measurement.

Firstly, I have only played with Delphi for a short while,
as I don't like Pascal that much. It does seem to me that
Delphi is very much a "idiot language". This almost always
means; easy to make pretty screens but performs like shite.

I get data from the par port using Turbo C (dos) and I
program in C-- with smidges of 8086 asm thrown in. You
can get a byte from the par port with something like a
thebyte=inportb(port_id)
which compiles down to a one-word cpu instruction and
on a 486 or pentium is virtually instantaneous.

Now I'm imagining (guessing) that Delphi has to beg
Bill for a chance to peek at the par port, and like most
windows programs will run very low performance.

I don't really have a solution for you, other than to
start programming for a high performance environment
(I am still making dos apps that run fabulously under
Win 95) OR, try finding a windows programming expert
who knows how to beg/force etc windows to give you
better access to the port.

Having done many years of fast hardware/software
interfacing with dos apps to the real world it never
ceases to amaze me just how PATHETIC windows is at
controlling anything more than a word processor.
:o)
-Roman

PS. Many people don't realise the par port has
more than 8 pins, you can get 12 bits input +
another bit for clk with no problems. This alone
will give you 1.5x the transfer rate.

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