From: brenner AT biochem DOT mpg DOT de (Markus Brenner)
Newsgroups: comp.os.msdos.djgpp
Subject: Help with high-speed data aquisition
Date: Mon, 07 Sep 1998 17:39:50 GMT
Organization: Max-Planck-Institut fuer Biochemie
Lines: 58
Message-ID: <6t15sc$7es$1@fu-berlin.de>
NNTP-Posting-Host: pcfr21.biochem.mpg.de (141.61.7.150)
Mime-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Transfer-Encoding: 8bit
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp
Precedence: bulk

Hello,

what I'm trying to do is write a conversion program for old C64 tapes. The 
tape recorder connects to an adapter at the parallel port. My program's task 
is to read a certain status bit of the lpt port fast enough to detect changing 
pulses and record pulse lengths. Eventually the program needs to save those 
pulses to a file.

What I do right now is:

I go into a busy wait for detecting alternating up/down pulses, then I read 
the timer to get the time delay since the last pulse. I store those into a 
huge memory buffer and afterwards do the calculation of pulse lengths from 
that data. Now, this all works pretty well except I got periodical wrong 
information (pulses too long), due to interrupts. (pulse transition gets lost 
during interrupt handling). See the code fragment at the end of the posting.

My question is: Can I turn off interrupts, and if yes, how? I could well 
confine myself to use this tool under DOS, so I don't really have scrupels to 
kill the multitasking :) OTOH I am not very familiar with protected mode and 
memory management, can I still use large memory (needed for the buffer) if I 
turn off interrupts?

Any help is appreciated!

cheers,

-markus


        // set up timer
        
        outp(0x43,0xb0);
        outp(0x42,0xffff & 0x00ff);
        outp(0x42,0xffff / 256);

        status = inp(0x61);
        outp(0x61,status | 1);  // start the timer

        bufferp = buffer;
        while (!(inp(LPT) & sense_pin))
        {
                while (inp(LPT) & read_pin);    // wait for '1' state
                while (!(inp(LPT) & read_pin)); // wait for '1'->'0' state

                *bufferp++ = inp(0x42);  // store timer data to huge buffer
                *bufferp++ = inp(0x42);
        }
        outp(0x61,status&~1);  // stop timer

----
 Markus Brenner             _           no matter how - how hard you try
  -==(UDIC)==-             ( )          in your own life, and through the years
      |\/|                --+--         with every up - must come a down
       \/                   |           enjoy the laughter and the tears
 Minstrel Dragon            |           of happiness     (Roger Taylor)
           Lord High Mucketty-muck of the UDIC Greybeards (tm)
 email: brenner AT biochem DOT mpg DOT de  *  WWW: http://www.biochem.mpg.de/~brenner/