Can I Connect 5V to a 3.3V Pin? Logic Levels and Level Shifters
Series navigation: Episode 1: The Roadmap · Episode 11 The problem: A 5 V module and a 3.3 V controller have matching signal names, but direct wiring may fail or damage an input. The goal: Check voltage limits and logic thresholds in both directions. The result: A decision process for direct connection, dividers, buffers, and level translators. AI-generated illustration of a mixed-voltage workbench. Verify every connection against the exact device data sheets. The connector fit, so I almost connected it The peripheral board had VCC , GND , TX , and RX . The microcontroller had pins with the same names. One board used 5 V and the other used 3.3 V. Matching names describe functions, not electrical compatibility. Before joining the wires, I needed answers to two separate questions: Will a HIGH output be recognized as HIGH by the receiver? Can the receiver safely tolerate the maximum voltage? Passing the first test does not guarantee the second. Four data-sheet value...