send continue loading commands periodically if initial load fails

Firmware/Marlin_main.cpp

@@ -129,6 +129,7 @@
 #include "sound.h"
 
 #include "cmdqueue.h"
+#include "io_atmega2560.h"
 
 // Macros for bit masks
 #define BIT(b) (1<<(b))
@@ -6911,8 +6912,16 @@ if((eSoundMode==e_SOUND_MODE_LOUD)||(eSoundMode==e_SOUND_MODE_ONCE))
               mmu_command(MMU_CMD_T0 + tmp_extruder);
 
               manage_response(true, true);
-              mmu_command(MMU_CMD_C0);
-              mmu_extruder = tmp_extruder; //filament change is finished
+#ifdef MMU_IDLER_SENSOR_PIN
+			  for (int i = 0; i < MMU_IDLER_SENSOR_ATTEMPTS_NR; i++) {
+				  if (PIN_GET(MMU_IDLER_SENSOR_PIN) == 0) break;		
+				  mmu_command(MMU_CMD_C0);
+				  manage_response(true, true);
+			  }
+#else 
+			  mmu_command(MMU_CMD_C0);
+#endif //MMU_IDLER_SENSOR_PIN
+			  mmu_extruder = tmp_extruder; //filament change is finished
 
               if (load_to_nozzle)// for single material usage with mmu
               {

Firmware/mmu.cpp

@@ -237,6 +237,9 @@ void mmu_loop(void)
 #endif //MMU_DEBUG
 				mmu_puts_P(PSTR("C0\n")); //send 'continue loading'
 				mmu_state = 3;
+#ifdef MMU_IDLER_SENSOR_PIN
+				mmu_idl_sens = 1; //enable idler sensor
+#endif //MMU_IDLER_SENSOR_PIN
 			}
 			else if (mmu_cmd == MMU_CMD_U0)
 			{
@@ -303,6 +306,9 @@ void mmu_loop(void)
 		{
 			if (PIN_GET(MMU_IDLER_SENSOR_PIN) == 0)
 			{
+#ifdef MMU_DEBUG
+				printf_P(PSTR("MMU <= 'A'\n"), mmu_finda);
+#endif //MMU_DEBUG  
 				mmu_puts_P(PSTR("A\n")); //send 'abort' request
 				mmu_idl_sens = 0;
 				//printf_P(PSTR("MMU IDLER_SENSOR = 0 - ABORT\n"));

Firmware/variants/1_75mm_MK3-EINSy10a-E3Dv6full.h

@@ -615,5 +615,6 @@
 #define MMU_HWRESET
 //#define MMU_DEBUG //print communication between MMU2 and printer on serial
 #define MMU_IDLER_SENSOR_PIN 62 //idler sensor @PK0 (digital pin 62/A8)
+#define MMU_IDLER_SENSOR_ATTEMPTS_NR 4 //max. number of attempts to load filament if first load failed
 
 #endif //__CONFIGURATION_PRUSA_H