DIY_EFI Digest V5 #168

[Peter D. Hipson]

Two items (ok, maybe four...) First I meant to say "the typical ECU has the
power of one of the original..."

Next power good comes from the power supply, and not the motherboard. Power
good is used to reset the motherboard to a known state when it is powered
up. This line will change state after the powersupply voltages are stable.
Power good doesn't care about -12 or -5 volts, either, in many
powersupplies powergood is run through a timer and a few gates--timer goes
off, and the gates ensure that there is +5V.

Not all systems will fail post if the -5/-12 is not present (btw: noone
uses the -5 volts--it was used for old style PC ram chips, and hasn't been
used since...) however the current drain from the -12 volt supply is
nominal. A cheap (they are about $10 converter can be used, they are
available with +12 in giving -12V out. CHeap and easy...

Java??? We don't need no stinking Java... <bg> I'd use either C or
assembler. Probably C is the best choice since it is powerful yet easy to
use. Develop under windows then port to plain DOS as needed for the final
product. 

At 11:00 AM 5/1/2000 -0700, you wrote:
>
>I'd say yes. PC's are used for industrial controllers as well. Remember, a
>typical CPU has the power of one of the original IBM PC (4.77 MHz), and a
>newer Pentium is about a hundred times faster! As well, DOS doesn't have
>the problem with interrupts as you can 'hog' the whole CPU. BTW, I doubt
>that an ECM could do one microsecond timing... That's a millionth of a
>second, very fast. Not much happens in an engine in that kind of time
>period... <g>
>
>- ------------------------------
>
>Date: Sun, 30 Apr 2000 15:34:41 -0800
>Date: Mon, 1 May 2000 11:05:24 -0400 
>From: Frederic Breitwieser <frederic at xephic.dynip.com>
>Subject: RE: Old 486 Board for ECU??
>
>Power Supply Issues:
>Actually, the PC requires +/- 5V, and +/- 12 V. Most system boards can
>"survive" without the negative power supply connections, as they are
>generally only used for Intel Above Board memory cards (if you remember
>those) and of course, the RS232 serial lines.
>
>The problem with dropping these voltages is that there is a line on the
>system board that provides a signal to the power supply, and its called
>"power good".  Without this line working properly, meaning all four voltages
>plus ground are there, most modern system boards won't boot.  Every
>manufacturer impliments this differently, so your mileage may vary.
>
>I have an old Micronics 486 all-in-one system board that has three slots on
>a riser card, which I'm not using (I yanked it), and built in video, IDE,
>par/ser, etc, and can boot off a CDROM drive.  Without the negative
>voltages, this system board boots, but the RS232 ports fail the POST
>process, requiring pressing F1 to continue.
>
>>I wonder how quickly your car will "boot up" if it has to boot from
>>floppy...  This is a (minor?) concern.
>
>POST testing takes anywhere from 5 seconds to a minute depending on the
>options/features you have enabled, as well as the amount of memory, and the
>size of the hard drives.  Larger memory/peripherals obviously take slightly
>longer.  Some system boards you can shorten this by enabling "quick POST" or
>something similar.  Still, there is a delay between applying power and
>usability.  A lot of the newer systemboards have a "green mode" where by a
>motherboard timing circuit powers down everything due to inactivity.  Some
>systemboards even have a jumper to force this.  Laptops have this, and its
>called "resume".  If you use a system that supports this, you can "boot" the
>car once, then leave it in "suspend" mode, so usability after turning the
>ignition key will be drastically shorter.
>
>Quick Boot:
>I think Axel suggested writing your own POST.  We are doing this now, and
>haven't finished it enough to test it, but the idea is to have the POST make
>assumptions.  Assume the memory is 64mb.  Assume the drive is "X" size.
>Assume both are present.  This way, the only delay is the drive spinning up,
>which in our case, would be drive "D" anyway.  Drive "C" is an ATA/IDE flash
>card that has an ide adaptor plugged into the system board.  200mb, with
>Linux installed.
>
>Java:
>I don't think Java would be fast enough on a simple systemboard (286/386)
>but its worth investigation.  We are using gcc, which comes with Linux.  C
>is one of the more portable languages, which Java is certainly comparible in
>this regard, but its compiled, resulting in "machine code" rather than "java
>executables".  I think it would be easier to use C which is much more
>stable, been around longer, and no more difficult to learn than Java.
>
>But, for humorous reasons, I will say, it would be neat to use a web-browser
>to reconfigure your EFI maps.  :)
>-
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>------------------------------
>

Thanks, 
        Peter Hipson (founder, NEHOG)
        1995 White NA Hummer Wagon
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