// Control a servo using a timer on a ESP32 (no ledc stuff)
// by misan April 2018

int servo=1500;
#define SERVO T2 // pin D11 on UC406 ESP32 UNO
hw_timer_t * timer1 = NULL; // servo

volatile boolean flip = false;

void IRAM_ATTR itr1(void) {
  if(flip) {
    digitalWrite(SERVO,LOW);
    flip = false;
    timerAlarmWrite(timer1, 20000, true);  // 20 ms between pulses
  }
  else {
    timerAlarmWrite(timer1, servo, true); //  servo pulse in microseconds
    flip = true;
    digitalWrite(SERVO,HIGH);
  }
}

void setup() {
  pinMode(SERVO,OUTPUT);
  timer1 = timerBegin(1, 80, true);
  timerAttachInterrupt(timer1, &itr1, true);
  timerAlarmWrite(timer1, 20000, true);
  timerAlarmEnable(timer1);
}

int angle=0;
void loop() {
  servo=1400+sin((angle++)/57.7)*800;
  delay(5);
}