Minimizing an ESP32-S3 Development Board Down to the Module Itself
The necessary components all fit on the back of the WROOM package.
Engineers have a fascination with optimization and removing unnecessary elements from a design. Chris Greening (AKA Atomic14 on YouTube) applied this fascination to an Espressif ESP32-S3 WROOM module. Typically you see these modules connected to a breakout board. However, Greening removed everything necessary to create a minimal USB-powered ESP32-S3 WROOM development board.
Greening starts with the schematic of a typical ESP32-S3 WROOM breakout board. You can find the ESP32-S3 system-on-module (SOM) mounted to such a board. These may contain passives to make the design more robust.
However, as Greening's explanation shows, many components are not (strictly) needed. For example, there are no pins for UART, JTAG, or Boot mode in this minimal ESP32 design. UART and JTAG functions are available via the S3's native USB support. Greening also eliminated the Boot mode pin. Keep in mind that you may need to short this pin to ground the first time you program the WROOM model.
With the UART and JTAG pins removed, how do you access the ESP32? Greening's next step was using a breadboard to connect a USB breakout board and linear regulator. Oh, and he included an LED (with a current limiting resistor!) for the mandatory blink sketch.
This stage of the reduction project demonstrates the minimal hardware necessary to connect an ESP32-S3 WROOM to a PCB via USB. But the Atomic14 video takes this concept one step further.
Next, Greening used polyimide (Katpon) tape to isolate the ground/thermal pads on the back of the WROOM module. Then, carefully, he mounted a linear regulator, decoupling capacitors, and the critical LED. All the breadboarded components fit after changing from through-hole to surface mount components.
Check out the entire ESP32 minimal dev board video for a detailed explanation (and justification) for removing the various components. You can also see the final version of the minimized kit, which does not even include the USB's breakout PCB!