If your introduction to digital electronics came more years ago than you’d care to mention, the chances are you did so with 5V TTL logic. Above 2V but usually pretty close to 5V is a logic 1 ...

In every technical document, summary, and description of the ESP8266, the ESP8266 is said to be a 3.3V part ... ESP8266 is 5V tolerant after all. If it is, great. We don’t need level converters ...

Higher drive strength can be required to trigger the direction detection circuit on the level shifter ICs for more demanding 5V circuits. Auto configure GPIO drive strength automatically after boot up ...

3.3V to Level Shifter 3.3V (low voltage side) TXD to Level Shifter Channel (low voltage side) On Arduino Uno R3 side: GND to Level Shifter GND (high voltage side) 5V to Level Shifter 5V (high voltage ...