D1 mini pro logical input voltage

Hello! I have a D1 mini pro board which accepts 3.3V as logical input. Now I'm connecting a MIDI In port to it and it has 5V logical output. It seems to work fine, but I'm sure it's not the right way to do it. As I'm not a geek in electronics, the question is - how to do it right?

5V logic levels might damage the ESP8266. Some people online claim that the pins are 5V-tolerant, but they are not.

From the official ESP8266 FAQ on the manufacturer’s website (under the “Peripherals” tab):

Are the GPIO pins 5V compatible?
No, they are not. While many applications may get away by using a resistor voltage divider or series resistor, we highly recommend using a proper logic level converter chip to interface with 5V logic. Not doing so may lead to damage to the ESP8266 in the long run.

From the datasheet (Table 5-1. Electrical Characteristics):

**Parameter ** **Min ** **Typical ** **Max ** **Unit **
VIL -0.3 - 0.25VIO V
VIH 0.75VIO - 3.6 V

Note that MIDI uses a current loop. The specification allows for both 5V and 3.3V MIDI circuits:
MIDI 1.0 Electrical Specification Update (CA-033) (2014). MMA Technical Standards Board / AMEI MIDI Committee.


Tell us about the "MIDI In port"?