PC's and EFI

[Mike Dillon]

Hi Ray ,

	I think you should reevaluate your approch to the problem,
 using a 100Mhz Pentium to process events happening at most in the 
 1-3 Khz range and running out of proceess power does not seem right.
 It seems you may be trying to use a hammer where a screwdriver is 
 more suited to  the task. 

Mike D.


 
> From diy_efi-owner at esl.eng.ohio-state.edu Thu Mar 19 00:12 CST 1998
>> From: cosmic.ray at juno.com (Raymond C Drouillard)
> 
> On Wed, 18 Mar 1998 01:23:15 -0600 "Terrie S. Watts" 
> 
> >Careful here.  I'm a pretty good programmer myself and I actually tried
> to
> >write a fuel injection (plus ignition control) on a 100 MHz Pentium
> laptop in
> >straight assembly code and still found by way of the O-scope that I
> wasn't
> >servicing multiple events quick enough.  It's much tougher than it would
> >first appear.  It can still be done but one needs to throw a little more
> >hardware at the problem to really get it working correctly.  The big
> problem
> >is that the CPU executes but a single instruction at a time and there is
> >quite a bit of things having to do with the engine all happening
> simultaneously.
> >I found myself in a priority battle trying to determine what absolutely
> has
> >to happen next and what could wait several clock cycles to get around
> to.
> >This strategy shows up on the scope and leads to quite a bit of head
> >scratching when the engine just doesn't seem to run up to snuff.
> 
> I would be the last one to try to argue my theory against your
> experience.  I based my information on the fact that someone made a
> usable system with a 4.77 MHZ PC running BASIC.  Based on what you said,
> I suspect that he got away with it because he was running a TBI system
> with no spark control.  Also, a 386/25 is many times faster than a PC.
> 
> The method I had in mind for controlling eight injecters wouldn't take
> much more processer time than running one.  The part of the program that
> controlls the would send a string of 1s and 0s to another routine that
> would send 00000000 to the parellel port when it receives a 0, and
> 00000001 or 00000010 or whatever (depending on which injecter is being
> fired) to the parellel port.
> 
> How did you control the time sharing?  If necessary, some custome device
> drivers could be written.
> 
> I saw some comments on using SCSI or IDE controllers.  That would
> certainly work. The approach I'm going with, howeverl, is the KIS (keep
> it simple) approach.  I want to use the devices that are designed to talk
> to something outside of the computer.  That saves some potential for
> hassle.
> 
> If you want to control eight spark coils, for instance, you could have
> the computer send out a couple bytes of data through a serial or parellel
> port.  The computer would instruct the controller which plug to fire and
> when to fire it.  The computer could then go on to other things.
> 
> The real trick is to not require the microprocessor to actually fire
> something at a specific time.  It should calculate when and how much,
> then load that data to something else.
> 
> A sound card could easily create a waveform that'll fire an injecter. 
> Just route it to the correct injecter (perhaps based on input from an
> RS232 port), and amplify it.  If you use a sound card with a programmable
> wave table, you can set up a variety of duty cycles and durations. 
> That'll offload a lot of processing from the microprocesser.
> 
> I don't know how much goofing around it would take to get the computer to
> read two game ports at once, but it shouldn't be too difficult.  It might
> just be a matter of assigning addresses for each one.  You'll need
> several analog inputs.  The output of the various sensors can be
> conditioned with op-amps and fed into the game port and sound card.  This
> would give you a total of six analog inputs. You will need an input for
> the coolant temperature, the air intake charge temperature, MAP (or MAF),
> and TPS.  Digitan inputs would be some kind of knock sensor (sound or
> ionization) and crank position.
> 
> Now you guys did it!  Got me thinking about a project that I don't really
> intend to undertake.  Sometimes, it's tough being a compulsive engineer.
> 
> Ray Drouillard, BSEE
> 
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