Sun May 11 10:47:41 EDT 2014


The simplest way to calibrate seems still to use frequency output of
an oscillator driven with the set current.  This is a measurement that
can be done very precisely on a uC.

So how to get it to oscillate?  Seems like a 555 is approprate.
However, can it be done with just a LM324N since I have one already?

Now for the oscillator we can cheat: charge cap with set current, but
drive discharge directly from microcontroller.  This way the frequency
is exact but the amplitude depends on the current.

Using a comparator input, this can be done in the PIC.  How fast can a
PIC respond?  Can the comparator out be used to drive the discharge
directly?  It seems so.