I have a piezoelectric sensor disk. I’m looking to take a output from this by using ESP32 microcontroller. But when I connect the sensor with microcontroller at GPIO 34, it gives only the positive peaks. But I need negative peaks also (i.e., I need to take a waveform as like in a oscilloscope).
Connections made like:
Sensor +ve – GPIO34
Sensor -ve – Ground

Here is my code to convert the digital readings that are readed from analogRead function into analog values.

void setup() {
  pinMode(34, INPUT);
  Serial.begin(9600);
}

void loop() {
  int sensorValue = analogRead(34); 
  float analogValue = sensorValue * (255.0 / 1023.0); // Convert the sensor value to analog value (8-bit)

  Serial.println(analogValue);

  delay(10);
}

My ESP32 has 12bit ADC and I’m working with Arduino IDE. Your solutions are most welcome.