Ide 1.8.19 Suddenly gives an error

Development Tools IDE 1.x
1

Hi Everyone.

I was programming a Nano Classic Old Bootloader , uploaded and the code worked.

Then I get this Error below.

Arduino: 1.8.19 (Windows 10), Board: "Arduino Nano, ATmega328P (Old Bootloader)"

C:\Program Files (x86)\Arduino\arduino-builder -dump-prefs -logger=machine -hardware C:\Program Files (x86)\Arduino\hardware -hardware C:\Users\mikee\AppData\Local\Arduino15\packages -tools C:\Program Files (x86)\Arduino\tools-builder -tools C:\Program Files (x86)\Arduino\hardware\tools\avr -tools C:\Users\mikee\AppData\Local\Arduino15\packages -built-in-libraries C:\Program Files (x86)\Arduino\libraries -libraries C:\Users\mikee\Documents\Arduino\libraries -fqbn=arduino:avr:nano:cpu=atmega328old -vid-pid=1A86_7523 -ide-version=10819 -build-path C:\Users\mikee\AppData\Local\Temp\arduino_build_486790 -warnings=none -build-cache C:\Users\mikee\AppData\Local\Temp\arduino_cache_994837 -prefs=build.warn_data_percentage=75 -prefs=runtime.tools.arduinoOTA.path=C:\Users\mikee\AppData\Local\Arduino15\packages\arduino\tools\arduinoOTA\1.3.0 -prefs=runtime.tools.arduinoOTA-1.3.0.path=C:\Users\mikee\AppData\Local\Arduino15\packages\arduino\tools\arduinoOTA\1.3.0 -prefs=runtime.tools.avr-gcc.path=C:\Users\mikee\AppData\Local\Arduino15\packages\arduino\tools\avr-gcc\7.3.0-atmel3.6.1-arduino7 -prefs=runtime.tools.avr-gcc-7.3.0-atmel3.6.1-arduino7.path=C:\Users\mikee\AppData\Local\Arduino15\packages\arduino\tools\avr-gcc\7.3.0-atmel3.6.1-arduino7 -prefs=runtime.tools.avrdude.path=C:\Users\mikee\AppData\Local\Arduino15\packages\arduino\tools\avrdude\6.3.0-arduino17 -prefs=runtime.tools.avrdude-6.3.0-arduino17.path=C:\Users\mikee\AppData\Local\Arduino15\packages\arduino\tools\avrdude\6.3.0-arduino17 -verbose C:\Users\mikee\Desktop\LCD_I2C_AnalogTest\LCD_I2C_AnalogTest.ino

C:\Program Files (x86)\Arduino\arduino-builder -compile -logger=machine -hardware C:\Program Files (x86)\Arduino\hardware -hardware C:\Users\mikee\AppData\Local\Arduino15\packages -tools C:\Program Files (x86)\Arduino\tools-builder -tools C:\Program Files (x86)\Arduino\hardware\tools\avr -tools C:\Users\mikee\AppData\Local\Arduino15\packages -built-in-libraries C:\Program Files (x86)\Arduino\libraries -libraries C:\Users\mikee\Documents\Arduino\libraries -fqbn=arduino:avr:nano:cpu=atmega328old -vid-pid=1A86_7523 -ide-version=10819 -build-path C:\Users\mikee\AppData\Local\Temp\arduino_build_486790 -warnings=none -build-cache C:\Users\mikee\AppData\Local\Temp\arduino_cache_994837 -prefs=build.warn_data_percentage=75 -prefs=runtime.tools.arduinoOTA.path=C:\Users\mikee\AppData\Local\Arduino15\packages\arduino\tools\arduinoOTA\1.3.0 -prefs=runtime.tools.arduinoOTA-1.3.0.path=C:\Users\mikee\AppData\Local\Arduino15\packages\arduino\tools\arduinoOTA\1.3.0 -prefs=runtime.tools.avr-gcc.path=C:\Users\mikee\AppData\Local\Arduino15\packages\arduino\tools\avr-gcc\7.3.0-atmel3.6.1-arduino7 -prefs=runtime.tools.avr-gcc-7.3.0-atmel3.6.1-arduino7.path=C:\Users\mikee\AppData\Local\Arduino15\packages\arduino\tools\avr-gcc\7.3.0-atmel3.6.1-arduino7 -prefs=runtime.tools.avrdude.path=C:\Users\mikee\AppData\Local\Arduino15\packages\arduino\tools\avrdude\6.3.0-arduino17 -prefs=runtime.tools.avrdude-6.3.0-arduino17.path=C:\Users\mikee\AppData\Local\Arduino15\packages\arduino\tools\avrdude\6.3.0-arduino17 -verbose C:\Users\mikee\Desktop\LCD_I2C_AnalogTest\LCD_I2C_AnalogTest.ino

Using board 'nano' from platform in folder: C:\Users\mikee\AppData\Local\Arduino15\packages\arduino\hardware\avr\1.8.6

Using core 'arduino' from platform in folder: C:\Users\mikee\AppData\Local\Arduino15\packages\arduino\hardware\avr\1.8.6

Warning: Board STMicroelectronics:stm32:STeaMi doesn't define a 'build.board' preference. Auto-set to: STM32_STEAMI

Detecting libraries used...

"C:\\Users\\mikee\\AppData\\Local\\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=10819 -DARDUINO_AVR_NANO -DARDUINO_ARCH_AVR "-IC:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\cores\\arduino" "-IC:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\variants\\eightanaloginputs" "C:\\Users\\mikee\\AppData\\Local\\Temp\\arduino_build_486790\\sketch\\LCD_I2C_AnalogTest.ino.cpp" -o nul

Alternatives for Esplora.h: [Esplora@1.0.4]

ResolveLibrary(Esplora.h)

  -> candidates: [Esplora@1.0.4]

"C:\\Users\\mikee\\AppData\\Local\\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=10819 -DARDUINO_AVR_NANO -DARDUINO_ARCH_AVR "-IC:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\cores\\arduino" "-IC:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\variants\\eightanaloginputs" "-IC:\\Program Files (x86)\\Arduino\\libraries\\Esplora\\src" "C:\\Users\\mikee\\AppData\\Local\\Temp\\arduino_build_486790\\sketch\\LCD_I2C_AnalogTest.ino.cpp" -o nul

Alternatives for Wire.h: [Wire@1.0]

ResolveLibrary(Wire.h)

  -> candidates: [Wire@1.0]

"C:\\Users\\mikee\\AppData\\Local\\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=10819 -DARDUINO_AVR_NANO -DARDUINO_ARCH_AVR "-IC:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\cores\\arduino" "-IC:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\variants\\eightanaloginputs" "-IC:\\Program Files (x86)\\Arduino\\libraries\\Esplora\\src" "-IC:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\libraries\\Wire\\src" "C:\\Users\\mikee\\AppData\\Local\\Temp\\arduino_build_486790\\sketch\\LCD_I2C_AnalogTest.ino.cpp" -o nul

Alternatives for hd44780.h: [hd44780@1.3.2]

ResolveLibrary(hd44780.h)

  -> candidates: [hd44780@1.3.2]

"C:\\Users\\mikee\\AppData\\Local\\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=10819 -DARDUINO_AVR_NANO -DARDUINO_ARCH_AVR "-IC:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\cores\\arduino" "-IC:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\variants\\eightanaloginputs" "-IC:\\Program Files (x86)\\Arduino\\libraries\\Esplora\\src" "-IC:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\libraries\\Wire\\src" "-IC:\\Users\\mikee\\Documents\\Arduino\\libraries\\hd44780" "C:\\Users\\mikee\\AppData\\Local\\Temp\\arduino_build_486790\\sketch\\LCD_I2C_AnalogTest.ino.cpp" -o nul

"C:\\Users\\mikee\\AppData\\Local\\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=10819 -DARDUINO_AVR_NANO -DARDUINO_ARCH_AVR "-IC:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\cores\\arduino" "-IC:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\variants\\eightanaloginputs" "-IC:\\Program Files (x86)\\Arduino\\libraries\\Esplora\\src" "-IC:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\libraries\\Wire\\src" "-IC:\\Users\\mikee\\Documents\\Arduino\\libraries\\hd44780" "C:\\Program Files (x86)\\Arduino\\libraries\\Esplora\\src\\Esplora.cpp" -o nul

"C:\\Users\\mikee\\AppData\\Local\\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=10819 -DARDUINO_AVR_NANO -DARDUINO_ARCH_AVR "-IC:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\cores\\arduino" "-IC:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\variants\\eightanaloginputs" "-IC:\\Program Files (x86)\\Arduino\\libraries\\Esplora\\src" "-IC:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\libraries\\Wire\\src" "-IC:\\Users\\mikee\\Documents\\Arduino\\libraries\\hd44780" "C:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\libraries\\Wire\\src\\Wire.cpp" -o nul

"C:\\Users\\mikee\\AppData\\Local\\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=10819 -DARDUINO_AVR_NANO -DARDUINO_ARCH_AVR "-IC:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\cores\\arduino" "-IC:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\variants\\eightanaloginputs" "-IC:\\Program Files (x86)\\Arduino\\libraries\\Esplora\\src" "-IC:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\libraries\\Wire\\src" "-IC:\\Users\\mikee\\Documents\\Arduino\\libraries\\hd44780" "C:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\libraries\\Wire\\src\\utility\\twi.c" -o nul

"C:\\Users\\mikee\\AppData\\Local\\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=10819 -DARDUINO_AVR_NANO -DARDUINO_ARCH_AVR "-IC:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\cores\\arduino" "-IC:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\variants\\eightanaloginputs" "-IC:\\Program Files (x86)\\Arduino\\libraries\\Esplora\\src" "-IC:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\libraries\\Wire\\src" "-IC:\\Users\\mikee\\Documents\\Arduino\\libraries\\hd44780" "C:\\Users\\mikee\\Documents\\Arduino\\libraries\\hd44780\\hd44780.cpp" -o nul

Generating function prototypes...

"C:\\Users\\mikee\\AppData\\Local\\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=10819 -DARDUINO_AVR_NANO -DARDUINO_ARCH_AVR "-IC:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\cores\\arduino" "-IC:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\variants\\eightanaloginputs" "-IC:\\Program Files (x86)\\Arduino\\libraries\\Esplora\\src" "-IC:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\libraries\\Wire\\src" "-IC:\\Users\\mikee\\Documents\\Arduino\\libraries\\hd44780" "C:\\Users\\mikee\\AppData\\Local\\Temp\\arduino_build_486790\\sketch\\LCD_I2C_AnalogTest.ino.cpp" -o "C:\\Users\\mikee\\AppData\\Local\\Temp\\arduino_build_486790\\preproc\\ctags_target_for_gcc_minus_e.cpp"

"C:\\Program Files (x86)\\Arduino\\tools-builder\\ctags\\5.8-arduino11/ctags" -u --language-force=c++ -f - --c++-kinds=svpf --fields=KSTtzns --line-directives "C:\\Users\\mikee\\AppData\\Local\\Temp\\arduino_build_486790\\preproc\\ctags_target_for_gcc_minus_e.cpp"

Compiling sketch...

"C:\\Users\\mikee\\AppData\\Local\\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 -MMD -flto -mmcu=atmega328p -DF_CPU=16000000L -DARDUINO=10819 -DARDUINO_AVR_NANO -DARDUINO_ARCH_AVR "-IC:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\cores\\arduino" "-IC:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\variants\\eightanaloginputs" "-IC:\\Program Files (x86)\\Arduino\\libraries\\Esplora\\src" "-IC:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\libraries\\Wire\\src" "-IC:\\Users\\mikee\\Documents\\Arduino\\libraries\\hd44780" "C:\\Users\\mikee\\AppData\\Local\\Temp\\arduino_build_486790\\sketch\\LCD_I2C_AnalogTest.ino.cpp" -o "C:\\Users\\mikee\\AppData\\Local\\Temp\\arduino_build_486790\\sketch\\LCD_I2C_AnalogTest.ino.cpp.o"

Compiling libraries...

Compiling library "Esplora"

"C:\\Users\\mikee\\AppData\\Local\\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 -MMD -flto -mmcu=atmega328p -DF_CPU=16000000L -DARDUINO=10819 -DARDUINO_AVR_NANO -DARDUINO_ARCH_AVR "-IC:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\cores\\arduino" "-IC:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\variants\\eightanaloginputs" "-IC:\\Program Files (x86)\\Arduino\\libraries\\Esplora\\src" "-IC:\\Users\\mikee\\AppData\\Local\\Arduino15\\packages\\arduino\\hardware\\avr\\1.8.6\\libraries\\Wire\\src" "-IC:\\Users\\mikee\\Documents\\Arduino\\libraries\\hd44780" "C:\\Program Files (x86)\\Arduino\\libraries\\Esplora\\src\\Esplora.cpp" -o "C:\\Users\\mikee\\AppData\\Local\\Temp\\arduino_build_486790\\libraries\\Esplora\\Esplora.cpp.o"

C:\Program Files (x86)\Arduino\libraries\Esplora\src\Esplora.cpp:54:26: error: 'A11' was not declared in this scope

 const byte ACCEL_Y_PIN = A11;

                          ^~~

C:\Program Files (x86)\Arduino\libraries\Esplora\src\Esplora.cpp:54:26: note: suggested alternative: 'A1'

 const byte ACCEL_Y_PIN = A11;

                          ^~~

                          A1

Using library Esplora at version 1.0.4 in folder: C:\Program Files (x86)\Arduino\libraries\Esplora 

Using library Wire at version 1.0 in folder: C:\Users\mikee\AppData\Local\Arduino15\packages\arduino\hardware\avr\1.8.6\libraries\Wire 

Using library hd44780 at version 1.3.2 in folder: C:\Users\mikee\Documents\Arduino\libraries\hd44780 

exit status 1

Error compiling for board Arduino Nano.

This is my working code that did Compile a few times.
Why STM32 is part of the compile , I have no Idea.

#include <Esplora.h>

// vi:ts=4
// ----------------------------------------------------------------------------
// HelloWorld - simple demonstration of lcd
// Created by Bill Perry 2016-07-02
// bperrybap@opensource.billsworld.billandterrie.com
//
// This example code is unlicensed and is released into the public domain
// ----------------------------------------------------------------------------
//
// This sketch is for LCDs with PCF8574 or MCP23008 chip based backpacks
// WARNING:
//	Use caution when using 3v only processors like arm and ESP8266 processors
//	when interfacing with 5v modules as not doing proper level shifting or
//	incorrectly hooking things up can damage the processor.
//
// Sketch prints "Hello, World!" on the lcd
//
// If initialization of the LCD fails and the arduino supports a built in LED,
// the sketch will simply blink the built in LED.
//
// NOTE:
//	If the sketch fails to produce the expected results, or blinks the LED,
//	run the included I2CexpDiag sketch to test the i2c signals and the LCD.
//
// ----------------------------------------------------------------------------
// LiquidCrystal compability:
// Since hd44780 is LiquidCrystal API compatible, most existing LiquidCrystal
// sketches should work with hd44780 hd44780_I2Cexp i/o class once the
// includes are changed to use hd44780 and the lcd object constructor is
// changed to use the hd44780_I2Cexp i/o class.

#include <Wire.h>
#include <hd44780.h>                       // main hd44780 header
#include <hd44780ioClass/hd44780_I2Cexp.h> // i2c expander i/o class header

hd44780_I2Cexp lcd; // declare lcd object: auto locate & auto config expander chip

// If you wish to use an i/o expander at a specific address, you can specify the
// i2c address and let the library auto configure it. If you don't specify
// the address, or use an address of zero, the library will search for the
// i2c address of the device.
// hd44780_I2Cexp lcd(i2c_address); // specify a specific i2c address
//
// It is also possible to create multiple/seperate lcd objects
// and the library can still automatically locate them.
// Example:
// hd4480_I2Cexp lcd1;
// hd4480_I2Cexp lcd2;
// The individual lcds would be referenced as lcd1 and lcd2
// i.e. lcd1.home() or lcd2.clear()
//
// It is also possible to specify the i2c address
// when declaring the lcd object.
// Example:
// hd44780_I2Cexp lcd1(0x20);
// hd44780_I2Cexp lcd2(0x27);
// This ensures that each each lcd object is assigned to a specific
// lcd device rather than letting the library automatically asign it.

// LCD geometry
const int LCD_COLS = 16;
const int LCD_ROWS = 2;

int analogRaw = 0;
float volts = 0;
int sum = 0;
int avgValue = 0;

void setup()
{
  Serial.begin(9600);
  int status;

  // initialize LCD with number of columns and rows:
  // hd44780 returns a status from begin() that can be used
  // to determine if initalization failed.
  // the actual status codes are defined in <hd44780.h>
  // See the values RV_XXXX
  //
  // looking at the return status from begin() is optional
  // it is being done here to provide feedback should there be an issue
  //
  // note:
  //	begin() will automatically turn on the backlight
  //
  status = lcd.begin(LCD_COLS, LCD_ROWS);
  if (status) // non zero status means it was unsuccesful
  {
    // hd44780 has a fatalError() routine that blinks an led if possible
    // begin() failed so blink error code using the onboard LED if possible
    hd44780::fatalError(status); // does not return
  }

  // initalization was successful, the backlight should be on now

  analogReference(EXTERNAL);
  lcd.print("Hello");
  delay(1000);
  lcd.clear();
}

void loop()
{
  for (int i = 0; i < 128; i++)
  {
    sum += analogRead(A0);
    delay(1);
  }
  avgValue = (sum / 128);
  lcd.setCursor(0, 1);
  lcd.print(avgValue);
  sum = 0;

  volts = ((3.3 / 1024) * avgValue) * 21.29; //21 = devider 10k+10k/1k

  lcd.setCursor(0, 0);
  lcd.print(volts,3);
  delay(500);

}
2

I would consider that noise; the real error is the undeclared A11. If the sketch eventually compiled, maybe you got caught in an update or similar.

3

Why are you using the Explora library with a Nano?

4

@david_2018

The compiler choose it for some reason.

The code compiled and uploaded before , like 2 minutes before the error.

Edit.
Just saw Explora is include , no Idea how that hapend.

5

Looking in the IDE, what are the board selections, etc. showing now?

6

Replying from my phone , miss the mouse.

I am not at that pc now , but I did check when I got the error.
Nano
Old Bootloader

Explora should not be included as noted by @david_2018 but how that hapend is a mistry.

7

Any chance a spurious menu click selected a different board during the compile process? I've never seen it happen with 1.x, BUT I don't change targets very often.

8

I copied the code I posted and remove "Explora" and compiled on my other PC , no errors.

Then I compiled again and during compilation change to ESP32 Wroom , no errors.

A few hours back.
I was just changing values on the 4th line from the bottom and the next compile gave an error.
I still have no idea how Explora got included.

9

Maybe you accidentally selected Sketch > Include Library > Esplora from the Arduino IDE menus? When you do that, Arduino IDE adds an #include directive for the library's header file to the current sketch.

10

That is way to many mouse clicks to happen by accident.

The only possible explanation is that maybe I swiped my hand over the key board to wipe away dust or something and pressed all the right keys.
I do that often.

11

I agree. My choice of the word "accidentally" was a poor one. My hypothesis was that you might have intentionally clicked on that menu item, not realizing that doing so would result in code being added to the current sketch.