Steve uses a perfboard version of this to test and demo various FRC electrical bits.

On this board are:

• 12VDC Input with protection against reverse polarity and overload
• generation of 5 volts using a classic linear regulator
• an LED that indicates that the 5v supply is OK
• two, three, or more copies of the basic DIO connector circuit
  • each with an LED to indicate “low” status on the signal pin

1 input wire assembly with anderson powerpole connector
1 rectifier diode - 1N4001, 1N4002, 1N4003, 1N4004, 1N4005, etc.
1 self-resetting PTC fuse, 0.5 to 1.5 amp
1 electrolytic capacitor, minimum 16 volts, 47uF.  (can be higher voltage or up to 470 uF)
2 0.1uF ceramic or monolithic capacitor
1 7805 linear regulator
1 LED for 5v power indicator; preferrably yellow or orange
1 resistor for power indicator.   typically 2.2K, less if not bright enough

One for each "DIO" header; quantities for a 4-port board:

4 three-pin 0.1" spaced header; approx. 0.4" tall posts for cable connection,
  tails long enough to solder
4 red LED for signal
4 resistor for red signal LED; typical 2.2K, less if not bright enough

The complete schematic is in Eastbots github: https://github.com/Team-4795/pcboards-2018/tree/master/fakerio1 And here is a PDF: https://github.com/Team-4795/pcboards-2018/raw/master/fakerio1/fakerio1.pdf

This schematic is actually more than complete: it has too much. There are two alternatives for power supply inputs; choose only one or the other.

Breaking down the schematic, here are the major portions.

This part is just a basic LED circuit that lights up when there is +5v power available at the DIO port connectors.

If you've commonly got a 12v battery or power supply handy in your build space or lab, build this portion. You might wire up the input to a set of red and black Anderson Powerpole connectors.

If you have a 5v power supply handy, for example a USB phone charger battery pack or wall brick, you might choose to build the 5v power portion.