List the pins you plan to use and the tool flags the usual mistakes before you solder. It catches duplicate pins, input-only pins used as outputs, flash pins, strapping pins and ADC2 pins used with Wi-Fi.
Rules come from the ESP32 and Uno pin behaviour described on this site. Boards from some makers differ; check your own board pinout.
How it is calculated
Each line is read as label, pin number and mode. The tool compares the pin with fixed lists for the board. On the ESP32 that means GPIOs 34 to 39 as input only, GPIOs 6 to 11 as flash pins, GPIOs 0, 2, 5, 12 and 15 as strapping pins, and the ADC2 pins that stop working when Wi-Fi is on. On the Uno it checks pins 0 and 1 for the USB serial and the six hardware PWM pins 3, 5, 6, 9, 10 and 11.
A worked example
The sample plan sets GPIO 12 as a PWM output, which the tool warns about because it is a strapping pin, flags GPIO 13 for analog use with Wi-Fi on, flags GPIO 35 because it is input only and cannot drive an output, and rejects GPIO 6 because it is a flash pin. Change the lines until the list is clean.
Common mistakes
- Assuming every GPIO number on the board silk-screen is free to use.
- Reading an analog sensor on an ADC2 pin and then turning on Wi-Fi.
- Wiring a motor driver input to a strapping pin and wondering why the board will not boot.
Related
ESP32 pinout for robotics, GPIO 12 boot failure, analogRead with Wi-Fi.
Last reviewed: November 2026. This tool runs in your browser and sends nothing anywhere. Treat its output as a first check, not a guarantee.