> Ok, I see that, using a regulator such a lm317 I can have a constant
> current, changing the resistance connected to it I can change the current
> value; and now the question arise: who to attach the outputs pins of the
> pic to change that resistance value?

You can use two pins to a 2 bit D/A made from resistors to get the four
voltage levels, then use these to drive a current source.  You could also
use a single PIC output pin with PWM.


********************************************************************
Olin Lathrop, embedded systems consultant in Littleton Massachusetts
(978) 742-9014, olin@embedinc.com, http://www.embedinc.com

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