• Design the PCB

I went back and forth on this a few times. There were two main choices to make:

• ESP8266, or
• ESP32

and

• Breakout board, or
• Implement directly.

In my first software work log I essentially decided on the ESP32. The ESP8266 was a bit cheaper, but it really doesn't have much overhead for me to work with. If I wanted to stick with micropython, which I did for other reasons, I would need to go up to the ESP32. I selected the ESP-WROOM-32D specifically.

Breakout board vs bare.

The next decision was around whether I wanted to design the PCB to accept a breakout board or the bare ESP-WROOM-32D package. The breakout board would be simpler, easier to solder, and provides a USB programming interface. The downside is that I couldn't find a consistently-available version of the board. Searching for “ESP32 breakout” or “ESP32 nodemcu” would yield a dozen slightly different boards. The Wimos D2 mini knockoff I was using earlier on in the project was more consistently knocked-off.

I'd hate for someone to be ordering the bits to build one of these robots and end up with a breakout board that didn't fit, or had the wrong pinout. So I decided to go with the bare ESP-WROOM-32D module. I had to implement some pull-ups and buttons to put it into a flashing state, but overall it wasn't too difficult.