Added redundant temp sensor

Marlin/Configuration.h

@@ -88,10 +88,14 @@
 // 55 is 100k thermistor - ATC Semitec 104GT-2 (Used in ParCan) (1k pullup)
 
 #define TEMP_SENSOR_0 -1
-#define TEMP_SENSOR_1 0
+#define TEMP_SENSOR_1 -1
 #define TEMP_SENSOR_2 0
 #define TEMP_SENSOR_BED 0
 
+// This makes temp sensor 1 a redundant sensor for sensor 0. If the temperatures difference between these sensors is to high the print will be aborted.
+#define TEMP_SENSOR_1_AS_REDUNDANT 
+#define MAX_REDUNDANT_TEMP_SENSOR_DIFF 5
+
 // Actual temperature must be close to target for this long before M109 returns success
 #define TEMP_RESIDENCY_TIME 10  // (seconds)
 #define TEMP_HYSTERESIS 3       // (degC) range of +/- temperatures considered "close" to the target one

Marlin/Configuration_adv.h

@@ -367,5 +367,8 @@ const unsigned int dropsegments=5; //everything with less than this number of st
   #undef BED_MAXTEMP
 #endif
 
+#if EXTRUDERS > 1 && defined TEMP_SENSOR_1_AS_REDUNDANT
+  #error "You cannot use  TEMP_SENSOR_1_AS_REDUNDANT if EXTRUDERS > 1"
+#endif
 
 #endif //__CONFIGURATION_ADV_H

Marlin/temperature.cpp

@@ -40,10 +40,13 @@
 int target_temperature[EXTRUDERS] = { 0 };
 int target_temperature_bed = 0;
 int current_temperature_raw[EXTRUDERS] = { 0 };
-float current_temperature[EXTRUDERS] = { 0 };
+float current_temperature[EXTRUDERS] = { 0.0 };
 int current_temperature_bed_raw = 0;
-float current_temperature_bed = 0;
-
+float current_temperature_bed = 0.0;
+#ifdef TEMP_SENSOR_1_AS_REDUNDANT
+  int redundant_temperature_raw = 0;
+  float redundant_temperature = 0.0;
+#endif
 #ifdef PIDTEMP
   float Kp=DEFAULT_Kp;
   float Ki=(DEFAULT_Ki*PID_dT);
@@ -471,7 +474,19 @@ void manage_heater()
         }
     }
     #endif
-
+    #ifdef TEMP_SENSOR_1_AS_REDUNDANT
+      if(fabs(current_temperature[1] - redundant_temperature) > MAX_REDUNDANT_TEMP_SENSOR_DIFF) {
+        disable_heater();
+        if(IsStopped() == false) {
+          SERIAL_ERROR_START;
+          SERIAL_ERRORLNPGM("Extruder switched off. Temperature difference between temp sensors is to high !");
+          LCD_ALERTMESSAGEPGM("Err: REDUNDANT TEMP ERROR");
+        }
+        #ifndef BOGUS_TEMPERATURE_FAILSAFE_OVERRIDE
+          Stop();
+        #endif
+      }
+    #endif
   } // End extruder for loop
 
   #if (defined(EXTRUDER_0_AUTO_FAN_PIN) && EXTRUDER_0_AUTO_FAN_PIN > -1) || \
@@ -644,7 +659,9 @@ static void updateTemperaturesFromRawValues()
         current_temperature[e] = analog2temp(current_temperature_raw[e], e);
     }
     current_temperature_bed = analog2tempBed(current_temperature_bed_raw);
-
+    #ifdef TEMP_SENSOR_1_AS_REDUNDANT
+      redundant_temperature =analog2temp(redundant_temperature_raw, 1);
+    #endif
     //Reset the watchdog after we know we have a temperature measurement.
     watchdog_reset();
 
@@ -1145,6 +1162,9 @@ ISR(TIMER0_COMPB_vect)
 #if EXTRUDERS > 1
       current_temperature_raw[1] = raw_temp_1_value;
 #endif
+#ifdef TEMP_SENSOR_1_AS_REDUNDANT
+      redundant_temperature_raw = raw_temp_1_value;
+#endif
 #if EXTRUDERS > 2
       current_temperature_raw[2] = raw_temp_2_value;
 #endif

Marlin/temperature.h

@@ -37,6 +37,9 @@ extern int target_temperature[EXTRUDERS];
 extern float current_temperature[EXTRUDERS];
 extern int target_temperature_bed;
 extern float current_temperature_bed;
+#ifdef TEMP_SENSOR_1_AS_REDUNDANT
+  extern float redundant_temperature;
+#endif
 
 #ifdef PIDTEMP
   extern float Kp,Ki,Kd,Kc;