I find myself fooling around making little adapters to prove out some code, messing with LEDs & resistors & such, wiring the same thing over & over. MrsCrossroads spent several hours yesterday adding LEDs & resistors to an Uno protoshield to support a test, which is working great, but I have to ask her to connect it up as needed as I have no idea what is wired to what, and there is no clean way to add labels with all the component legs in the way.
I figured why not come up with something a bit more stable (& Labelled!) for testing, with a boat load of typically used components (see attached):
Status LEDs (20 for Uno, 40 for Mega) with 1K current limit resistors for ~ 3mA current flow)
Buttons - not sure how many yet, probably 8, in an extended area from the ICSP header on Uno and outside of the 22-53 IO header on the Mega.
Rotary Encoder (right angle) & filter circuit
2 trim type Pots (screw driver adjustable)
2 shift registers driving 2 7-segment displays - maybe change to MAX7219 & 8 digits of Bubble display (lot more cost tho - ~$9.25 vs ~$3.75)
2 Servo connectors for offboard servos
2A Servo only power supply (rest of board is powered by the underlying Uno/Mega)
So I’ve got this board all placed up in Eagle, with just a couple things left I am working on/ waffling on:
Servo power supply - I have 7805/TO220 flat on the board for a place holder for now, going to change that to a chip/inductor switching power supply for a 2A supply to 2 servos.
2 pots - I have 2 single turn 5K pots there now. Was thinking to just use them as reference levels - but maybe instead leave the high side open so it could be used for offboard signal voltage divider? 10K value instead?
There are a lot of LEDs - 20 for Uno size board, 36 for a Mega. Replace a bank (or some quantity) of those with a 74HC4050 so up to six 3.3V level signals could go out? (with 3.3V from the underlying Uno/Mega).
Squeeze in a couple N-channel MOSFETs to sink current to drive relays or other high current load?
I am picturing I will personally populate it with male pins and just connect stuff with wirewrap wire, make it solid for testing, and easy to remove & rewire. Others might leave the holes blank and solder in wires instead for something more permanent/harder to change. I did that with a 1284 Bobuino2 recently, and regretted soldering in wires as soon as I started. Especially when I found 2 wires that I missed by 1 hole each in placement.
Will post a board layout pic shortly.