Stage 2 · Lesson 4 of 7
Logic levels: 3.3 V and 5 V
Digital pins read a voltage as low or high using thresholds, and each chip family has its own. The classic Arduino Uno runs at 5 V. The , and the Raspberry Pi all run at , and a 5 V signal into a 3.3 V-only pin can destroy it.
Some STM32 pins are 5 V tolerant, marked FT in the datasheet's pin table, but not all of them, and the Raspberry Pi and ESP32 pins are not. Use a level shifter (a small board that translates between voltages) or a divider for one-way signals. Check each module's supply and output voltage before wiring.
Common trapconnecting a 5 V sensor output straight to an ESP32 or Pi pin because it "worked for a minute", then losing the pin, or the board, later.
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Resources for this stage
Start with
- BookFreeAll About Circuits Textbook
All About Circuits · Beginner
Free: read the DC volume chapters on Ohm's law, series and parallel circuits and dividers
Keep handy
Also worth your time
Why 3.3 V and 5 V parts need care, and how level shifting solves it