New AVR internals to combat the AVR Pin Peripheral Conflict

Marlin/src/HAL/AVR/HAL.cpp

@@ -61,23 +61,40 @@ void save_reset_reason() {
   wdt_disable();
 }
 
+#include "registers.h"
+
+MarlinHAL::MarlinHAL() {
+  TERN_(HAL_AVR_DIRTY_INIT, _ATmega_resetperipherals()); // Clean-wipe the device state.
+}
+
 void MarlinHAL::init() {
   // Init Servo Pins
-  #define INIT_SERVO(N) OUT_WRITE(SERVO##N##_PIN, LOW)
   #if HAS_SERVO_0
-    INIT_SERVO(0);
+    OUT_WRITE(SERVO0_PIN, LOW);
   #endif
   #if HAS_SERVO_1
-    INIT_SERVO(1);
+    OUT_WRITE(SERVO1_PIN, LOW);
   #endif
   #if HAS_SERVO_2
-    INIT_SERVO(2);
+    OUT_WRITE(SERVO2_PIN, LOW);
   #endif
   #if HAS_SERVO_3
-    INIT_SERVO(3);
+    OUT_WRITE(SERVO3_PIN, LOW);
   #endif
 
   init_pwm_timers();   // Init user timers to default frequency - 1000HZ
+
+  #if PIN_EXISTS(BEEPER) && ENABLED(HAL_AVR_DIRTY_INIT) && DISABLED(ATMEGA_NO_BEEPFIX)
+    // Make sure no alternative is locked onto the BEEPER.
+    // This fixes the issue where the ATmega is constantly beeping.
+    // Might disable other peripherals using the pin; to circumvent that please undefine one of the above things!
+    // The true culprit is the AVR ArduinoCore that enables peripherals redundantly.
+    // (USART1 on the GeeeTech GT2560)
+    // https://www.youtube.com/watch?v=jMgCvRXkexk
+    _ATmega_savePinAlternate(BEEPER_PIN);
+
+    OUT_WRITE(BEEPER_PIN, LOW);
+  #endif
 }
 
 void MarlinHAL::reboot() {

Marlin/src/HAL/AVR/HAL.h

@@ -187,7 +187,7 @@ class MarlinHAL {
 public:
 
   // Earliest possible init, before setup()
-  MarlinHAL() {}
+  MarlinHAL();
 
   // Watchdog
   static void watchdog_init()    IF_DISABLED(USE_WATCHDOG, {});