SG90 Servo jumps to 90 degrees at startup

[Haghiri75]

I have a sg90 servo, powered from an external lab supply with a common ground connection to my Arduino Uno, and I control it with the following code:

#include <Servo.h>

Servo myServo;
int servoState;

void setup() {
  // put your setup code here, to run once:
  myServo.attach(11);

  Serial.begin(9600);
  Serial.println("Initialization done, wait for 2 seconds...");
  Serial.print("Initial servo state: ");
  Serial.println(servoState);
  delay(2000);
  Serial.println("Now at your service");

}

void loop() {
  // put your main code here, to run repeatedly:
  String servoCommand = Serial.readString();
  

  if (servoCommand == "up\n") {
    while (servoState > 0) {
      myServo.attach(11);
      myServo.write(servoState - 1);
      servoState -= 1;
      delay(25);
    }

    Serial.println("UP");
    Serial.print("Current Servo Angle: ");
    Serial.println(servoState);
  }

  if (servoCommand == "down\n") {
    while (servoState < 90) {
      myServo.write(servoState + 1);
      servoState += 1;
      delay(25);
    }

    Serial.println("DOWN");
    Serial.print("Current Servo Angle: ");
    Serial.println(servoState); 
  }

  if (servoCommand == "middle\n") {
    if (servoState < 45) {
      while (servoState < 45) {
        myServo.write(servoState + 1);
        servoState += 1;
        delay(25);

      }
    }
    else {
      while (servoState > 45) {
        myServo.write(servoState - 1);
        servoState -= 1;
        delay(25);
      }
    }

    Serial.println("MIDDLE");
    Serial.print("Current Servo Angle: ");
    Serial.println(servoState);
  }


}

It is okay and controls my servo perfectly, but has a huge problem. When I power up my circuit, servo first jumps to the maximum of 90 degrees then starts getting my desired commands.

I have something in my mind, how can I keep the last state of the servo in my code, then write it to the servo when I power up the circuit? or how can I just prevent servo from jumping at startup?

[UKHeliBob]

If you do a .write() before the .attach() the servo will move to the specified angle rather than the default which is 90 degrees

[Haghiri75]

I tried this and it worked fine. My problem is now keeping the last state of the servo. any ideas for that?

[UKHeliBob]

Save it EEPROM but be careful how often you do it because the EEPROM has a limited number of safe writes to each address, albeit about 10,000 from memory

[JCA34F]

You need a controlled shutdown function to save the current servo position to EEPROM before power off, then recall it on next startup.
Compiles but untested, type "sd[ENTER]" to shutdown and hopefully save servo position for next startup.

#include <Servo.h>
#include <EEPROM.h>

Servo myServo;

int servoState;
const uint16_t eeAdd = 0x3FE; // last int address in EEPROM

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  EEPROM.get(eeAdd,servoState);
  if(servoState > 180)
    servoState = 0;
  myServo.write(servoState);
  myServo.attach(11);
  Serial.println("Initialization done, wait for 2 seconds...");
  Serial.print("Initial servo state: ");
  Serial.println(servoState);
  delay(2000);
  Serial.println("Now at your service");
}

void loop() {
  // put your main code here, to run repeatedly:
  String servoCommand = Serial.readString();
  
  if (servoCommand == "sd\n") { // type "sd[ENTER]" for shutdown
    EEPROM.put(eeAdd,servoState);
    delay(50);
    while(true);  // loop here forever, power off.
  }  
  if (servoCommand == "up\n") {
    while (servoState > 0) {
      //myServo.attach(11);
      myServo.write(servoState - 1);
      servoState -= 1;
      delay(25);
    }
    Serial.println("UP");
    Serial.print("Current Servo Angle: ");
    Serial.println(servoState);
  }
    if (servoCommand == "down\n") {
    while (servoState < 90) {
      myServo.write(servoState + 1);
      servoState += 1;
      delay(25);
    }
    Serial.println("DOWN");
    Serial.print("Current Servo Angle: ");
    Serial.println(servoState); 
  }
    if (servoCommand == "middle\n") {
    if (servoState < 45) {
      while (servoState < 45) {
        myServo.write(servoState + 1);
        servoState += 1;
        delay(25);
       }
    }
    else {
      while (servoState > 45) {
        myServo.write(servoState - 1);
        servoState -= 1;
        delay(25);
      }
    }

    Serial.println("MIDDLE");
    Serial.print("Current Servo Angle: ");
    Serial.println(servoState);
  }
}