A thought...

[Kalle Pihlajasaari]

Hi,

> Yes, but how will you mount it in your car? How much power can you afford 
> to use to run this PC? The benefits might be swallowed by the additional
> Horsepower lost in the new alternator required to run the thing.
> 
> You have to do things in Real-time, and no RTOS is easily accessable
> for this system?
> 
> How will you isloate this computer system and it's connectors from vibration
> inherent in automobiles?
> 
> How do you do the timing control without a TPU, and/or PWM waveform generator?
> 
> How do you get timing control tighter than 55 ms? (the timer tick on PC boards
> are 1/18th of a second).
> 
> How do you program in 80386 assembler and have few bugs?

I hope you are kidding, There are more RTOS's for bigger processors
than the embedded ones, you can get DOS, UNIX and NT variants plus
many other less common ones.

If you use the PC104 formfactor the connectors are 0.1" pin grids which
are very reliable (not perfect mind you) and loads better than the 
ISA edge connector.  The PC104 designs also gave a full set of standard
periferals on the card to give you a diagnostics RX232 port (2 of) a
parallel port for one interrupt in line and 4 data in lines and 
11 data data out lines.  You also get drop in ROM, FLASH, SRAM
cards that are available in automotive temperatures.  Many vehicle
tracking systems make use of embedded PCs in cars and trucks.

The sixe of PC104 is about 3.5" x 3.5" and as such smaller than the
standard car controller (still needs driver circuitry which will make up
for it).  Also if you find the 386 just does not get you there drop in a 
486 or pentium, YOUR CODE STAYS THE SAME (or almost, depending on
coding style and ability) and the rest of the hardware does not need
to be changed just the processor card.

There is a bult in timer in the PC which is programmable and does get 
set to a much higher speed in most OSs besided DOS.  You have one timer
channel output on the speaker port with an independant gate on the
output and input of the timer channel.  you can get many multi IO
cards with analog and digital and timer functions all on one card.

You can connect all of the functions to the PC with ribbon cable (yuck)
and there will be no vibration stress.

80386 assembler is about the same as al lthe others and there are
a lot more development tools to work with for a PC than any other 
processor out there if I guess right.

Cheers 
-- 
Kalle Pihlajasaari     kalle at data.co.za
Interface Products     Box 15775, Doornfontein, 2028, South Africa
+27 (11) 402-7750      Fax: +27 (11) 402-7751