Mail Archives: djgpp/1996/02/06/03:38:04
Larry Blanchard (larryb AT comtch DOT iea DOT com) wrote:
: James T. Sweeten Jr. (sweeten AT belgarath DOT nwscc DOT sea06 DOT navy DOT mil) wrote:
: : I have a question concerning the timer interrupt 8.
: : What is the difference between the protected mode int8 and the real mode
: : int 8?
: : I need to output a value on a d/a board at specific intervals. I
: : originally did this with borland by installing my own timer interrupt routine.
: : I was able to get down to 100 micro second (10khz) resolution. I am trying to
: : do the same thing using djgpp. I have read the faq and have also gotten
: : pctime13.zip (This has milisecond resolution for djgpp). I modified the
: : interrupt routines in pctime13.zip, (gccint8.c), to output the data to the
: : d/a board ok but I can't get down to 100 micro second resolution. With an
: : input value of 3000 hz I get a nice 1500 hz square wave. With a value of
: : 4000 hz it works for a while but then locks the machine up. Any help would
: : be appreciated.
: : I am using 1.12m4 on a 486/66.
: I recently had exactly the same need, tried just what you did (also on a
: 2/66), and got almost the same results. Mine sometimes even hung at 3000.
: Apparently, the overhead of the DPMI stuff is just too great for high
: frequencies. I gave up on djgpp and did it in real mode. I can do 20Khz
: with no problems.
Try DJGPP 2.0, it works much better for interrupts.
I have used 8Khz interrupts just fine on a DX4/100.
The code in the interrupt does the following:
reading and converting 6 10-bit absolute encoders
controlling 6 stepper motors using step/dir bits complete with
speed control and acceleration
reading 12 16-bit force measurements from a DSP-based card
reading 56 bits of digital I/O (sensors) from a PIO card
All of this is in C, and is using approximately 50% of the CPU time. (The
foreground task is using GRX to display all of this info, and control it)
--
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Raymond H Kelm II New Image Software, Inc
rhk AT farpoint DOT newimage DOT com Makers of Image BBS
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