http://igm.univ-mlv.fr/~masson/v2/Teachings/IMC-4201C/RTAI/rta

Add a bit of hardware to the Maximite for the fast stuff  and forget all
this complicated real time linux stuff. It all has a very very VERY
steep learning curve. One could get bogged down for months.

Linux was designed for personal computers.. not  real time control of
machines.

Maximite is truly easy to learn and use.


This schematic will handle the injectors with out Maximite
intervention unless there is a change in pulse width or injection
frequency needed. Total control over injection frequency down to
one injection per second.

Ignitions are simple pulses and 7500 RPM gives you 8 milliseconds
to deal with it and everything else. No problem for the Maximite.

Linux might be fine for moving maps and EFIS's because they are
not really real time applications. You have seconds to update things.

Paul Lamar

Here is another hardware trick to cut the software overhead.
Most people are using RX8 or Chevy LS1 ignition coils. These coils
requires a fixed 2 to 4 msec dwell time regardless of the RPM.
No more no less. Too much and they overheat and fail.Too little
and the spark is weak.

This is a bear to do in software. In the Maximite you could set up
a 4 msec tick interrupt and count it until it was time to fire
the blocks. A better way is to use 555's set up as a one shot's
with a 4 ms period. That way all it needs is a one or two usec
negative going trigger pulse when it is time to fire. The timing
of this pulse relative to top dead centre is a function of RPM.
A calculation must be made for that. Low RPM almost no advance.
High RPM could be 50% of the 8 msec TDC pulse frequency.

IMHO Tracy got it wrong in pure software and burned out a lot of
LS1 coils before he fashioned an elaborate coil cooling system

Come to think of it Mazda may have got it wrong in the RX8 I think.
Early RX8's failed a lot of coils.

I am curious how they do it in Mega Squirt.

Paul Lamar


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