KiCad design of simple testbench for microcontrollers.
The resistor networks should be pairwise identical; I've used 680Ω for the LED resistors, with blue & green LEDs (note that the LEDs are connected to the closest pin, so top and bottom row are each connected to both resistor networks), and 1kΩ for the ladder resistors.
So what is the "ladder" part good for? It's the world's most primitive analog computer, a.k.a a voltage divider that can be used to generate a wide range of fractions of VCC, according to the formula printed on the board:
To generate a particular voltage, connect your analog input pin to one or several of the pins
in the top row (next to the
+) and one or several in the bottom row (next to
If VCC (applied to the
+ pin) is 5V, then
5V * (1 / (1+1)) = 2.5V(as will
5V * (1 / (1+2)) = 1.6V.
5V * (2 / (2+1)) = 3.2V.
5V * (1 / 1+1+2) = 1.25V.
PCB available at OSH Park