Rename BEEPER to BEEPER_PIN

For consistency with other pins, allowing use of `PIN_EXISTS` macro.

Marlin/Conditionals.h

     #define WRITE_FAN(v) WRITE(FAN_PIN, v)
   #endif
 
-  #define HAS_BUZZER ((defined(BEEPER) && BEEPER >= 0) || defined(LCD_USE_I2C_BUZZER))
+  #define HAS_BUZZER (PIN_EXISTS(BEEPER) || defined(LCD_USE_I2C_BUZZER))
 
   #if defined(NUM_SERVOS) && NUM_SERVOS > 0
     #ifndef X_ENDSTOP_SERVO_NR

Marlin/buzzer.cpp

     if (freq > 0) {
       #if ENABLED(LCD_USE_I2C_BUZZER)
         lcd_buzz(duration, freq);
-      #elif defined(BEEPER) && BEEPER >= 0 // on-board buzzers have no further condition
-        SET_OUTPUT(BEEPER);
+      #elif PIN_EXISTS(BEEPER) // on-board buzzers have no further condition
+        SET_OUTPUT(BEEPER_PIN);
         #ifdef SPEAKER // a speaker needs a AC ore a pulsed DC
-          //tone(BEEPER, freq, duration); // needs a PWMable pin
+          //tone(BEEPER_PIN, freq, duration); // needs a PWMable pin
           unsigned int delay = 1000000 / freq / 2;
           int i = duration * freq / 1000;
           while (i--) {
-            WRITE(BEEPER,HIGH);
+            WRITE(BEEPER_PIN, HIGH);
             delayMicroseconds(delay);
-            WRITE(BEEPER,LOW);
+            WRITE(BEEPER_PIN, LOW);
             delayMicroseconds(delay);
            }
         #else // buzzer has its own resonator - needs a DC
-          WRITE(BEEPER, HIGH);
+          WRITE(BEEPER_PIN, HIGH);
           delay(duration);
-          WRITE(BEEPER, LOW);
+          WRITE(BEEPER_PIN, LOW);
         #endif
       #else
         delay(duration);

Marlin/pins_3DRAG.h

 #define HEATER_BED_PIN     9    // BED
 
 #if ENABLED(ULTRA_LCD) && ENABLED(NEWPANEL)
-  #undef BEEPER
-  #define BEEPER -1
+  #undef BEEPER_PIN
+  #define BEEPER_PIN -1
 
   #undef LCD_PINS_RS
   #undef LCD_PINS_ENABLE
 
 #else
 
-  #define BEEPER 33
+  #define BEEPER_PIN 33
 
 #endif // ULTRA_LCD && NEWPANEL

Marlin/pins_AZTEEG_X3.h

 
 #if ENABLED(VIKI2) || ENABLED(miniVIKI)
 
- #define BEEPER 33
+ #define BEEPER_PIN 33
+
  // Pins for DOGM SPI LCD Support
  #define DOGLCD_A0  31 
  #define DOGLCD_CS  32 

Marlin/pins_AZTEEG_X3_PRO.h

 
 #undef FAN_PIN
 #define FAN_PIN             6 //Part Cooling System
-#define BEEPER             33
+#define BEEPER_PIN         33
 #define CONTROLLERFAN_PIN   4 //Pin used for the fan to cool motherboard (-1 to disable)
 //Fans/Water Pump to cool the hotend cool side.
 #define EXTRUDER_0_AUTO_FAN_PIN   5
 //LCD Pins//
 
  #if ENABLED(VIKI2) || ENABLED(miniVIKI)
-  #define BEEPER           33
+  #define BEEPER_PIN       33
  // Pins for DOGM SPI LCD Support
   #define DOGLCD_A0        44
   #define DOGLCD_CS        45

Marlin/pins_ELEFU_3.h

 #define TEMP_2_PIN         1  //ANALOG NUMBERING
 #define TEMP_BED_PIN       0  //ANALOG NUMBERING
 
-#define BEEPER             36
+#define BEEPER_PIN         36
 
 #define KILL_PIN           -1
 

Marlin/pins_GEN7_CUSTOM.h

 //#define TX_ENABLE_PIN       12
 //#define RX_ENABLE_PIN       13
 
-#define BEEPER -1
+#define BEEPER_PIN -1
 #define SDCARDDETECT -1
 #define SUICIDE_PIN -1    //has to be defined; otherwise Power_off doesn't work
 

Marlin/pins_MEGACONTROLLER.h

 #endif
 
 #ifdef MINIPANEL
-    #define BEEPER 46
+    #define BEEPER_PIN 46
     // Pins for DOGM SPI LCD Support
     #define DOGLCD_A0  47
     #define DOGLCD_CS  45

Marlin/pins_MEGATRONICS.h

 #define HEATER_BED_PIN     10   // BED
 #define TEMP_BED_PIN       14   // ANALOG NUMBERING
 
-#define BEEPER             33   // AUX-4
+#define BEEPER_PIN         33   // AUX-4
 
 #if defined(ULTRA_LCD) && defined(NEWPANEL)
 

Marlin/pins_MEGATRONICS_2.h

   #define TEMP_BED_PIN 14 // ANALOG NUMBERING
 #endif
 
-#define BEEPER 64
+#define BEEPER_PIN 64
 
 
 #define LCD_PINS_RS 14

Marlin/pins_MEGATRONICS_3.h

 #define TEMP_2_PIN   (TEMP_SENSOR_2 == -1 ?   9 : 12) // ANALOG NUMBERING
 #define TEMP_BED_PIN (TEMP_SENSOR_BED == -1 ? 8 : 14) // ANALOG NUMBERING
 
-#define BEEPER 61
+#define BEEPER_PIN 61
 
 #define LCD_PINS_RS 32
 #define LCD_PINS_ENABLE 31

Marlin/pins_MINIRAMBO.h

 #if ENABLED(ULTRA_LCD)
   #define KILL_PIN 32
   #if ENABLED(NEWPANEL)
-   //arduino pin which triggers an piezzo beeper
-    #define BEEPER 84      // Beeper on AUX-4
+
+    #define BEEPER_PIN 84      // Beeper on AUX-4
     #define LCD_PINS_RS 82
     #define LCD_PINS_ENABLE 18
     #define LCD_PINS_D4 19

Marlin/pins_MINITRONICS.h

 #define HEATER_BED_PIN 3 // BED
 #define TEMP_BED_PIN 6 // ANALOG NUMBERING
 
-#define BEEPER -1
-
+#define BEEPER_PIN -1
 
 #define LCD_PINS_RS -1
 #define LCD_PINS_ENABLE -1

Marlin/pins_PRINTRBOARD.h

 
 #if ENABLED(ULTRA_LCD) && ENABLED(NEWPANEL)
   //we have no buzzer installed
-  #define BEEPER -1
+  #define BEEPER_PIN -1
   //LCD Pins
   #if ENABLED(LCD_I2C_PANELOLU2)
     #define BTN_EN1 27  //RX1 - fastio.h pin mapping 27
 #endif // ULTRA_LCD && NEWPANEL
 
 #if ENABLED(VIKI2) || ENABLED(miniVIKI)
- #define BEEPER 32 //FastIO
+ #define BEEPER_PIN 32 //FastIO
  // Pins for DOGM SPI LCD Support
  #define DOGLCD_A0  42 //Non-FastIO
  #define DOGLCD_CS  43 //Non-FastIO

Marlin/pins_RAMBO.h

 #if ENABLED(ULTRA_LCD)
   #define KILL_PIN 80
   #if ENABLED(NEWPANEL)
-   //arduino pin which triggers an piezzo beeper
-    #define BEEPER 79      // Beeper on AUX-4
+
+    #define BEEPER_PIN 79      // Beeper on AUX-4
+
     #define LCD_PINS_RS 70
     #define LCD_PINS_ENABLE 71
     #define LCD_PINS_D4 72
     #define SDCARDDETECT 81    // Ramps does not use this port
 
   #else //!NEWPANEL - old style panel with shift register
-    //arduino pin witch triggers an piezzo beeper
-    #define BEEPER 33    No Beeper added
+
+    #define BEEPER_PIN 33    // No Beeper added
+
     //buttons are attached to a shift register
     // Not wired this yet
     // #define SHIFT_CLK 38
 #endif // ULTRA_LCD
 
 #if ENABLED(VIKI2) || ENABLED(miniVIKI)
- #define BEEPER 44
+ #define BEEPER_PIN 44
  // Pins for DOGM SPI LCD Support
  #define DOGLCD_A0  70 
  #define DOGLCD_CS  71 

Marlin/pins_RAMPS_13.h

     #endif
 
     #if ENABLED(REPRAP_DISCOUNT_SMART_CONTROLLER)
-      #define BEEPER 37
+      #define BEEPER_PIN 37
 
       #define BTN_EN1 31
       #define BTN_EN2 33
       #define SDCARDDETECT 49
       #define LCD_SDSS 53
       #define KILL_PIN 41
-      #define BEEPER 23
+      #define BEEPER_PIN 23
       #define DOGLCD_CS 29
       #define DOGLCD_A0 27
       #define LCD_PIN_BL 33
     #elif defined(MINIPANEL)
-       #define BEEPER 42
+       #define BEEPER_PIN 42
        // Pins for DOGM SPI LCD Support
        #define DOGLCD_A0  44
        #define DOGLCD_CS  66
        #define BTN_ENC 59  //the click switch
        //not connected to a pin
        #define SDCARDDETECT 49
+
     #else
-      // arduino pin which triggers an piezzo beeper
-      #define BEEPER 33  // Beeper on AUX-4
+
+      #define BEEPER_PIN 33  // Beeper on AUX-4
 
       // buttons are directly attached using AUX-2
       #if ENABLED(REPRAPWORLD_KEYPAD)
 
     #endif
   #else // !NEWPANEL (Old-style panel with shift register)
-    // Arduino pin to trigger a piezzo beeper
-    #define BEEPER 33   // No Beeper added
+
+    #define BEEPER_PIN 33   // No Beeper added
 
     // Buttons are attached to a shift register
     // Not wired yet

Marlin/pins_RIGIDBOARD.h

 
 #if ENABLED(RIGIDBOT_PANEL)
 
-  #undef BEEPER
-  #define BEEPER -1
+  #undef BEEPER_PIN
+  #define BEEPER_PIN -1
 
   #undef SDCARDDETECT
   #define SDCARDDETECT 22
 
 #elif defined(REPRAP_DISCOUNT_SMART_CONTROLLER)
 
-  #undef BEEPER
-  #define BEEPER -1
+  #undef BEEPER_PIN
+  #define BEEPER_PIN -1
 
   #undef  SDCARDDETECT
   #define SDCARDDETECT 22

Marlin/pins_RUMBA.h

 #define SDPOWER            -1
 #define SDSS               53
 #define SDCARDDETECT       49
-#define BEEPER             44
+#define BEEPER_PIN         44
 #define LCD_PINS_RS        19
 #define LCD_PINS_ENABLE    42
 #define LCD_PINS_D4        18

Marlin/pins_SANGUINOLOLU_11.h

 #if ENABLED(ULTRA_LCD) && ENABLED(NEWPANEL)
 
   // No buzzer installed
-  #define BEEPER -1
+  #define BEEPER_PIN -1
 
   // LCD Pins
   #if ENABLED(DOGLCD)
         #define LCD_PINS_RS     30 //CS chip select /SS chip slave select
         #define LCD_PINS_ENABLE 29 //SID (MOSI)
         #define LCD_PINS_D4     17 //SCK (CLK) clock
-        #define BEEPER          27 // Pin 27 is take by LED_Pin, but Melzi LED do nothing with Marlin and I take this pin for BEEPER.... See here > [github.com] , If you want use this pin with Gcode M42 instead BEEPER
+        #define BEEPER_PIN      27 // Pin 27 is taken by LED_PIN, but Melzi LED does nothing with Marlin so this can be used for BEEPER_PIN. You can use this pin with M42 instead of BEEPER_PIN.
       #else         // Sanguinololu 1.3
         #define LCD_PINS_RS      4 
         #define LCD_PINS_ENABLE 17 
 
 #elif ENABLED(MAKRPANEL)
 
-  #define BEEPER                29
+  #define BEEPER_PIN            29
 
   // Pins for DOGM SPI LCD Support
   #define DOGLCD_A0             30

Marlin/pins_SAV_MKI.h

 #define ALARM_PIN          -1
 #define SDCARDDETECT       -1
 
-#define BEEPER             -1
+#define BEEPER_PIN         -1
 #define LCD_PINS_RS        -1
 #define LCD_PINS_ENABLE    -1
 #define LCD_PINS_D4        -1

Marlin/pins_TEENSYLU.h

 #endif
 
 #if ENABLED(ULTRA_LCD) && ENABLED(NEWPANEL)
-  //we have no buzzer installed
-  #define BEEPER -1
   //LCD Pins
+
+  #define BEEPER_PIN -1
+
   #if ENABLED(LCD_I2C_PANELOLU2)
     #define BTN_EN1 27  //RX1 - fastio.h pin mapping 27
     #define BTN_EN2 26  //TX1 - fastio.h pin mapping 26

Marlin/pins_ULTIMAIN_2.h

 #define MOTOR_CURRENT_PWM_RANGE 2000
 #define DEFAULT_PWM_MOTOR_CURRENT  {1300, 1300, 1250}
 
-//arduino pin witch triggers an piezzo beeper
-#define BEEPER 18
+#define BEEPER_PIN 18
 
 #define LCD_PINS_RS 20
 #define LCD_PINS_ENABLE 15

Marlin/pins_ULTIMAKER.h

 
 #if ENABLED(ULTRA_LCD)
 
+  #define BEEPER_PIN 18
+
   #if ENABLED(NEWPANEL)
-  //arduino pin witch triggers an piezzo beeper
-    #define BEEPER 18
 
     #define LCD_PINS_RS 20
     #define LCD_PINS_ENABLE 17
     //buttons are directly attached
     #define BTN_EN1 40
     #define BTN_EN2 42
-    #define BTN_ENC 19  //the click
+    #define BTN_ENC 19
 
     #define SDCARDDETECT 38
 
   #else //!NEWPANEL - Old style panel with shift register
 
-    //arduino pin witch triggers an piezzo beeper
-    #define BEEPER 18
-
     //buttons are attached to a shift register
     #define SHIFT_CLK 38
     #define SHIFT_LD 42

Marlin/ultralcd.cpp

       #define LCD_FEEDBACK_FREQUENCY_DURATION_MS (1000/6)
     #endif    
     lcd.buzz(LCD_FEEDBACK_FREQUENCY_DURATION_MS, LCD_FEEDBACK_FREQUENCY_HZ);
-  #elif defined(BEEPER) && BEEPER >= 0
+  #elif PIN_EXISTS(BEEPER)
     #ifndef LCD_FEEDBACK_FREQUENCY_HZ
       #define LCD_FEEDBACK_FREQUENCY_HZ 5000
     #endif