I placed an application hint that demonstrates how to
interface a hall effect sensor to an ATmega328 using
interrupts. See
http://wiblocks.luciani.org/docs/app-notes/pico1trc-hall-effect.html
The Honeywell SS345 is a unipolar hall-effect sensor that can
be powered from a supply that ranges from 2.7V to 7V.
I wired the sensor using the prototype area of my PICO1TRC
(Loading...).
When the magnetic field changes an interrupt routine is called and
a flag is set. When the flag is set the main loop of the program
outputs the time and state of the magnetic field.
(* jcl *)
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