A thought...

[Roger Heflin]

Michael F. Sargent wrote:
> 
> > You have to do things in Real-time, and no RTOS is easily accessable
> > for this system?
> 
> There are lots of RTOS's available for PC's (i.e. RTEMS or QNX).

You would not even need a RTOS.  Most control systems micros have no OS
at
all.  They do everything themselves.

> BTW: With an engine turning at 6,000 RPM (100 RPS), the engine turns
> over 360 degrees every 1/100 of a second. With interupts at 10,000 per
> second, that means an interupt will occur every 3.6 degrees. That should
> be accurate enough for most people. But if you want greater accuracy,
> just reduce the divisor to 33, and you'll get interupts every degree.
> (Admittedly, your ISR will need to be pretty tightly coded even on a
> Pentium in this case.)

You probably would not use any ISRs.  It is not like the computer has
anything better to do.  Probably just one loop, no ISRs at all.   Let
the clock
run free (ignore its interrupts) and make sure that you loop will
execute
in less than 1 rotation of the clock (more than 18.2 times a second -
should
be pretty easy), then just scan all required sensors (including the
clock) every pass and make the decisions based on that.  ISR only
complicated things unnecessarly, you only use the if the computer has
something better to do with its time. 
 

It really doesn't sound that hard to do.

-- 
Roger Heflin                    rah at horizon.hit.net