#include <ESP32Servo.h>

static const int servo_pin = 12;

int min_us = 500;
int max_us = 2400;

Servo servo;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  servo.attach(servo_pin, min_us, max_us);
}

void loop() {
  for (int pos = 90; pos >= 0; pos--) { // sweep from 0 degrees to 180 degrees
    // in steps of 1 degree
    servo.write(pos);              
    delay(20);                       // waits 20ms for the servo to reach the position
  }
}