Thanks a lot, Peter, but this would give equal period steps, and what I
need is equal speed steps (a constant acceleration is dv/dt and the
period of the timer is the inverse of that).

Thanks anyway.

Any other hints?

Francisco


Peter L. Peres wrote:

>On Mon, 5 Aug 2002, Francisco Ares wrote:
>
>
>
>>Hi all PIClisters.
>>
>>Can someone point me to an algorithim to do accelaration for a stepper
>>motor controller?
>>
>>My controller uses one timer overflow ISR to switch the phases of the
>>motor, so the speed is calculated through the period register of this timer.
>>
>>I need to calculate different values for the period register for a
>>constant (or close to constant) acceleration, preferably "on-the-fly",
>>inside the same ISR.
>>
>>My first atempts resulted in that the final speed was never reached
>>because of accumulating errors in calculations.
>>
>>
>
>For each 'step' of acceleration you compute Time1 = Time0 - dt and set the
>timer to that. dt is set previously = (Starttime - Fasttime)/Numsteps,
>where Numsteps is the number of intermediate speeds you need and Starttime
>a timer value that corresponds to a minimum safe starting speed. When
>Time0 == Fasttime you have arrived to max speed.
>
>Peter
>
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