Library that will load for some sketches and not for others.

What were the libraries, or the code, and I'll see if I can reproduce the problem

Also, when you verify the script it shows which ones it's found. You could compare those that work with the ones that don't.

Here a (reformatted) sample of the output when I 'verify' one of my sketches

The -I lines show where the libraries are looked for

Detecting libraries used...
/home/mark/.arduino15/packages/arduino/tools/avr-gcc/7.3.0-atmel3.6.1-arduino7/bin/avr-g++
-c
-g
-Os
-w
-std=gnu++11
-fpermissive
-fno-exceptions
-ffunction-sections
-fdata-sections
-fno-threadsafe-statics
-Wno-error=narrowing
-flto
-w
-x
c++
-E
-CC
-mmcu=atmega328p
-DF_CPU=16000000L
-DARDUINO=10607
-DARDUINO_AVR_NANO
-DARDUINO_ARCH_AVR
-I/home/mark/.arduino15/packages/arduino/hardware/avr/1.8.6/cores/arduino
-I/home/mark/.arduino15/packages/arduino/hardware/avr/1.8.6/variants/eightanaloginputs
/tmp/arduino-sketch-75B0016B03FA06C15AD1462BB02B01BF/sketch/Tank_Controller_Code.ino.cpp
-o
/dev/null

This is the code that will not use the library. Thanks for the look-see. Quince

[code]
#include <Servo.h>
#include <Wire.h>
#include <QMC5883L.h> // QMC5883L library

// QMC5883L I2C address
#define QMC5883L_ADDRESS 0x0D

// Create a Servo object
Servo myservo;

// Create an instance of the QMC5883L class
QMC5883L compass;

int counter = 90;
int previousHeading = 0;
unsigned long start_time = 0;

void setup() {
  // Start I2C communication
  Wire.begin();

  // Initialize the QMC5883L
  compass.init();

  // Setup Serial Monitor
  Serial.begin (115200);

  // Attach servo on pin 9 to the servo object
  myservo.attach(9);
}

void loop() {
  // Read the current heading from the QMC5883L
  int currentHeading = compass.getHeading();

  // Check if the current heading is different from the previous heading
  if (abs(currentHeading - previousHeading) > 3) {
    // Update the servo position
    counter = map(currentHeading, 0, 360, 0, 180);
    myservo.write(counter);

    Serial.print("Position: ");
    Serial.println(counter);

    // Reset the start time
    start_time = millis();
  }

  // Check if no movement is detected for 500ms
  if (millis() - start_time > 500) {
    // Return the servo to the initial counter
    myservo.write(90);
    counter = 90;
    Serial.println("Returning to initial position");
  }

  // Update previousHeading with the current heading
  previousHeading = currentHeading;
}
[/code]

@quince The message about not finding a library is board specific. For instance yesterday I was looking at a library issue and found several versions of the library, each stored within the specific boards folder structure. Also confusion over <lib.h> vs "lib.h" can lead to unexpected results.

Posting some of your code usually the first page that shows what header files are included is enough in this case. Also a screenshot of the IDE preferences, and IDE Tools menu as seen in attached picture

There are many variants for QMC5883.

The most popular seems to be QMC5883LCompass

However, it's include file, QMC5883LCompass.h, isn't what your using in the sketch.

Do you have a url for the download of the one you're using?

IGNORE THE ABOVE

I see you attached the original file.

You're using the Compass version, so your include should be

#include <QMC5883LCompass.h>

@quince You're using a more recent/different version of the library.

The 'compass' variable/object needs to be of type: QMC5883LCompass

and

currentDirection has become getAzimuth

I think the revised code should be

#include <Servo.h>
#include <Wire.h>
#include <QMC5883LCompass.h> // QMC5883L library

// QMC5883L I2C address
#define QMC5883L_ADDRESS 0x0D

// Create a Servo object
Servo myservo;

// Create an instance of the QMC5883L class
QMC5883LCompass compass;

int counter = 90;
int previousHeading = 0;
unsigned long start_time = 0;

void setup() {
  // Start I2C communication
  Wire.begin();

  // Initialize the QMC5883L
  compass.init();

  // Setup Serial Monitor
  Serial.begin (115200);

  // Attach servo on pin 9 to the servo object
  myservo.attach(9);
}

void loop() {
  // Read the current heading from the QMC5883L
  // int currentHeading = compass.currentHeading();
  int currentHeading = compass.getAzimuth();

  // Check if the current heading is different from the previous heading
  if (abs(currentHeading - previousHeading) > 3) {
    // Update the servo position
    counter = map(currentHeading, 0, 360, 0, 180);
    myservo.write(counter);

    Serial.print("Position: ");
    Serial.println(counter);

    // Reset the start time
    start_time = millis();
  }

  // Check if no movement is detected for 500ms
  if (millis() - start_time > 500) {
    // Return the servo to the initial counter
    myservo.write(90);
    counter = 90;
    Serial.println("Returning to initial position");
  }

  // Update previousHeading with the current heading
  previousHeading = currentHeading;
}

Thank you all. I will give it a try. Quince