Often in microcontroller-Systems jumpers are used
to select options. Now assume the following setup:
You can use two GPIO pins of an AVR. These pins
have no additional functinalities. Only these
two pins are accessible, no connections to GND
or VCC are possible.
The question now is: How many options can you
select/detect by connecting different electrical components/networks to the two pins ?
The simplest are: open/short.
Or you may use a resistor. Can you differentiate
some resistance values (the internal pullup
is not very accurate)? What can you do with
capacitors and peraps diodes ?
What ideas come to your mind ?