Josh Criswold wrote:
>
> Last night I was wondering about the feasibility of
> using a PDA as the "brains" for a vehicle engine
> management system. I don't know much about the
> hardware of the various Palm OS PDAs, but I do know
> C(2+) and Java and that there are compilers (though
> limited) for both of these languages on the Palm OS.
> The question I can't answer is will a compiled C
> program be fast enough with PDA hardware? Also, is
> the I/O fast enough?
>
> The PDA would have to receive signal between 1 and
> 9kHz (representing RPM), determine the frequency, look
> up the frequency on a table correlating the input
> frequency and output frequency, and output a frequency
> up to .6kHz probably 15 time/sec. Simultaneously, it
> would receive a voltage representing throttle
> position, and look up the input frequency and throttle
> position on a table correlating these with a pulse
> width and frequency up to .6kHz.
>
> There would be no need to access the display.
>
> Power is not a problem b/c the PDA would be hardwired.
>
>
> Some signal conditioning would be performed by
> circuits outside the PDA.
>
> So, feasible?
>
Interesting idea.
The processor is probably fast enough, but you'd almost certainly need
to completely bypass both the Palm OS and the real-time kernel to get
the required accuracy, which needs to be in the microsecond range. The
fuel injector pulses and spark triggers need to go out at very precise
angles (as measured by the crankshaft position) and to do this
absolutely requires a hard real time system.
For certain things a compiled C program will be fast enough, such as
monitoring the throttle position and velocity and doing table lookups to
get fuel injector pulse width and spark advance/retard. When it comes to
sending the pulses to the engine I think you'll have more success using
a separate dedicated processor with onboard A/D and D/A.
--
Tony <who did this for a living once upon a time>
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