The first thing that came to my mind to add a slider was to use a potentiometer in series with a 1K resistor.

Then I remembered that the ground is not available at the I/O header.....

This is bad... very bad.... It leaves me with only two options.

• Add the GND using a wire
• Use the RESET pin
• Hey, there is a third option here! dont't ya think this project has already many buttons? use them smartly!!!