AD keyboard (5 keys on one analog pin) with ESP32

Supply 3.3-5 V Bus ANALOG

Pins and ESP32 wiring

Pin	Role	ESP32 pin	Notes
GND	Ground	GND
VCC	Power	3V3	Use 3V3 so OUT never goes above 3.3 V
OUT	Analog output	D34	A different voltage for each key: read it on an ADC1 pin (GPIO 32 to 39)

Suggested wiring for the 30-pin ESP32 DevKit, avoiding flash, input-only and strapping pins. BoardPilot checks it for you as you wire.

void setup() { Serial.begin(115200); }

void loop() {
  int mv = analogReadMilliVolts(34);  // OUT on GPIO 34
  Serial.println(mv);
  delay(200);
}

DFRobot ADKeyboard module (DFR0075) wiki, Resistor ladder: each key gives a different analog value
Espressif ESP-IDF Programming Guide, ADC: input range and attenuation

Part data: CC BY 4.0, free to reuse with credit to BoardPilot.