So I'm working on a code that basically receives x and y coordinates and stores them in a variable. Whenever a coordinate is received, it goes through a conditional statement to store them in a variable, x and y, then passes it to a servo mover function. This servo motor function then moves according to what's given. It works well, but, as the values get updated over time, the servo' position always resets then goes back to where it was, again and again. Even when the coordinates are kept the same, it just resets then returns to its position over and over again.

How do I make it so that not only does it not reset then return to where it was but instead make it move to where it is supposed to go, but also to stop it from resetting anyway when the position is kept the same?

The below code is what I tried to do to basically alleviate the "position reset when coordinate is the same" issue. Unfortunately, it did not work.

bool constant = false;
// Rest of code inbetween, irrelevant to issue

// Relevant codes below
void statusCodes() {
  if (received_str == "1") {
    Serial.println("Raspberry Pi - Connection Established");
  } else if (received_str == "2") {
    Serial.println("Raspberry Pi - Data Received");
  } else if (received_str == "100") {
    Serial.println("Raspberry Pi - Status OK");
  } else if (received_str[0] == '(' ) {
    Serial.println("Coordinates Received, Ready to Delete Target!");
    if (constant == true) { // checks if this constant boolean is true
      movement = false;
    } else {
      movement == true;
    int r = sscanf(received_str.c_str(), "(%d, %d)", &x, &y);
    Serial.print("X: ");
    Serial.print("Y: ");

void onDetectTarget() {
  x = map(x, 0, 1023, 0, 180);
  y = map(y, 0, 1023, 0, 180);
  if (movement == true) {
    for (pos = 0; pos <= x; pos += 1) {
    movement = false; // corrected
    pos = 0; // corrected

void compareOldNew() {
  x_old = x;
  y_old = y;
  if (x == x_old && y == y_old) {
    constant = true;
  } else {
    constant = false;

1 Answer 1


In onDetectTarget() you use this for loop

for (pos = 0; pos <= x; pos += 1) {

So every time movement is true, the servo will run again from zero to the target position. So it won't "reset", but it will approach the new target value always from the zero position. You have two options to correct that:

  • If you just want to reach the target position, just replace the for loop with a single myservo.write(x).

  • If you want the servo to move slower to its new target position, you need to save the last set position of the servo in a variable and then run the for loop from that value up to the new target value. So declare a corresponding variable (for example on global scope):

      int current_pos = 0;

    Then run the for loop from that position to the new target position:

      for(pos = current_pos; pos <= x; pos += 1)

    And after the for loop you can set current_pos to the new servo position:

      current_pos = x;

And I guess this happens also, when the values don't change, because you never change the constant variable. You haven't implemented any check if the values are constant. (At least you haven't shown such a code and you claim the rest of the code is irrelevant)

  • Thanks for your response man, that was really helpful. I thought I had to use a for loop to constantly write the value but with your explanation, everything made more sense to me. As for detecting the same position, i later researched and found that you could basically use static variables to store older values, compare them and have a flag to see if they were equal or not. Mar 11, 2022 at 23:18

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