Writing down ESP32 pin assignments in a spreadsheet is a good to plan things out ahead of time, but it isn't a robot until wires are connected and circuits completed. I'll test the plan on my cardboard box rover testbed. When I cut out the holes for all those motors and servos, I left a space open in the middle for circuitry. Since this is a testbed to prove out a plan, I want the flexibility to easily test things incrementally as I build things piece by piece. It would also be nice to easily fix problems I will undoubtedly discover during testing. Both of these desires pointed to a breadboard and jumper wire instead of a more permanent soldered solution.

In my collection of ESP32 development kits, there is a very important differentiation for this task: some of these modules are 0.1" wider than the others. This difference is critically important for a breadboard prototype: the narrower modules leave one breadboard hole exposed on either side for jumper wiring, in contrast the wider module would completely block all holes on one side. To use wider modules on a breadboard, all the wires have to run underneath the module making them much less experimentation-friendly than their thinner counterparts. For this particular project I'm using an ESP32 dev module I purchased from this Amazon link (*) but there's no guarantee the vendor wouldn't change things up in the future.

One problem with the narrower module is that its compact layout left no space for labels on the visible side of the board. Rather than laboriously looking up charts and counting pins every time a wire connection is to be made, some clever people have designed paper templates to help with the task. I found one that matched my ESP32 dev kit at this link. Checking against my dev kit's schematic, I see it is functionally correct though there is an inconsequential cosmetic typo of GIOP instead of GPIO. Printing out the PDF at 100% scale will match size with the real thing, which I then put between the breadboard and my ESP32 as I pushed the ESP32 dev kit in to the breadboard. Metal pins have no problem punching through that paper, and the paper is not conductive enough to cause problems with the circuit.

Having a pinout reference immediately available cuts down on frustration and mistakes, and I liked the idea so much I wanted them for my DRV8833 breakout boards as well. Because those breakout boards also had visible pin labels on their downward-facing side of the board. I didn't have the skill to draw up a nice template using graphics design software, but using a sheet of paper I could create a hand-written reference.

(*) Disclosure: As an Amazon Associate I earn from qualifying purchases.