✨ More flexible redundant temp sensor (#22085)

Marlin/Configuration.h

 #define TEMP_SENSOR_PROBE 0
 #define TEMP_SENSOR_CHAMBER 0
 #define TEMP_SENSOR_COOLER 0
+#define TEMP_SENSOR_REDUNDANT 0
 
 // Dummy thermistor constant temperature readings, for use with 998 and 999
 #define DUMMY_THERMISTOR_998_VALUE  25
 //#define MAX31865_SENSOR_OHMS_1      100
 //#define MAX31865_CALIBRATION_OHMS_1 430
 
-// Use temp sensor 1 as a redundant sensor with sensor 0. If the readings
-// from the two sensors differ too much the print will be aborted.
-//#define TEMP_SENSOR_1_AS_REDUNDANT
-#define MAX_REDUNDANT_TEMP_SENSOR_DIFF 10
-
 #define TEMP_RESIDENCY_TIME         10  // (seconds) Time to wait for hotend to "settle" in M109
 #define TEMP_WINDOW                  1  // (°C) Temperature proximity for the "temperature reached" timer
 #define TEMP_HYSTERESIS              3  // (°C) Temperature proximity considered "close enough" to the target
 #define TEMP_CHAMBER_WINDOW          1  // (°C) Temperature proximity for the "temperature reached" timer
 #define TEMP_CHAMBER_HYSTERESIS      3  // (°C) Temperature proximity considered "close enough" to the target
 
+/**
+ * Redundant Temperature Sensor (TEMP_SENSOR_REDUNDANT)
+ *
+ * Use a temp sensor as a redundant sensor for another reading. Select an unused temperature sensor, and another
+ * sensor you'd like it to be redundant for. If the two thermistors differ by TEMP_SENSOR_REDUNDANT_MAX_DIFF (°C),
+ * the print will be aborted. Whichever sensor is selected will have its normal functions disabled; i.e. selecting
+ * the Bed sensor (-1) will disable bed heating/monitoring.
+ *
+ * Use the following to select temp sensors:
+ *    -5 : Cooler
+ *    -4 : Probe
+ *    -3 : not used
+ *    -2 : Chamber
+ *    -1 : Bed
+ *   0-7 : E0 through E7
+ */
+#if TEMP_SENSOR_REDUNDANT
+  #define TEMP_SENSOR_REDUNDANT_SOURCE     1  // The sensor that will provide the redundant reading.
+  #define TEMP_SENSOR_REDUNDANT_TARGET     0  // The sensor that we are providing a redundant reading for.
+  #define TEMP_SENSOR_REDUNDANT_MAX_DIFF  10  // (°C) Temperature difference that will trigger a print abort.
+#endif
+
 // Below this temperature the heater will be switched off
 // because it probably indicates a broken thermistor wire.
 #define HEATER_0_MINTEMP   5

Marlin/Configuration_adv.h

   #define PROBE_BETA                   3950    // Beta value
 #endif
 
+#if TEMP_SENSOR_REDUNDANT == 1000
+  #define REDUNDANT_PULLUP_RESISTOR_OHMS   4700    // Pullup resistor
+  #define REDUNDANT_RESISTANCE_25C_OHMS    100000  // Resistance at 25C
+  #define REDUNDANT_BETA                   3950    // Beta value
+#endif
+
 //
 // Hephestos 2 24V heated bed upgrade kit.
 // https://store.bq.com/en/heated-bed-kit-hephestos2

Marlin/src/HAL/LPC1768/tft/xpt2046.h

   XPT2046_Z2 = 0x40 | XPT2046_CONTROL | XPT2046_DFR_MODE,
 };
 
-#if !defined(XPT2046_Z1_THRESHOLD)
+#ifndef XPT2046_Z1_THRESHOLD
   #define XPT2046_Z1_THRESHOLD 10
 #endif
 

Marlin/src/HAL/STM32/tft/xpt2046.h

   XPT2046_Z2 = 0x40 | XPT2046_CONTROL | XPT2046_DFR_MODE,
 };
 
-#if !defined(XPT2046_Z1_THRESHOLD)
+#ifndef XPT2046_Z1_THRESHOLD
   #define XPT2046_Z1_THRESHOLD 10
 #endif
 

Marlin/src/HAL/STM32F1/tft/xpt2046.h

   XPT2046_Z2 = 0x40 | XPT2046_CONTROL | XPT2046_DFR_MODE,
 };
 
-#if !defined(XPT2046_Z1_THRESHOLD)
+#ifndef XPT2046_Z1_THRESHOLD
   #define XPT2046_Z1_THRESHOLD 10
 #endif
 

Marlin/src/MarlinCore.cpp

   SETUP_RUN(HAL_init());
 
   // Init and disable SPI thermocouples; this is still needed
-  #if TEMP_SENSOR_0_IS_MAX_TC
+  #if TEMP_SENSOR_0_IS_MAX_TC || (TEMP_SENSOR_REDUNDANT_IS_MAX_TC && TEMP_SENSOR_REDUNDANT_SOURCE == 0)
     OUT_WRITE(MAX6675_SS_PIN, HIGH);  // Disable
   #endif
-  #if TEMP_SENSOR_1_IS_MAX_TC
+  #if TEMP_SENSOR_1_IS_MAX_TC || (TEMP_SENSOR_REDUNDANT_IS_MAX_TC && TEMP_SENSOR_REDUNDANT_SOURCE == 1)
     OUT_WRITE(MAX6675_SS2_PIN, HIGH); // Disable
   #endif
 

Marlin/src/gcode/temp/M105.cpp

 
   #if HAS_TEMP_SENSOR
 
-    thermalManager.print_heater_states(target_extruder
-      #if ENABLED(TEMP_SENSOR_1_AS_REDUNDANT)
-        , parser.boolval('R')
-      #endif
-    );
+    thermalManager.print_heater_states(target_extruder OPTARG(HAS_TEMP_REDUNDANT, parser.boolval('R')));
 
     SERIAL_EOL();
 

Marlin/src/inc/Conditionals_post.h

  * Temp Sensor defines
  */
 
-#define ANY_TEMP_SENSOR_IS(n) (TEMP_SENSOR_0 == (n) || TEMP_SENSOR_1 == (n) || TEMP_SENSOR_2 == (n) || TEMP_SENSOR_3 == (n) || TEMP_SENSOR_4 == (n) || TEMP_SENSOR_5 == (n) || TEMP_SENSOR_6 == (n) || TEMP_SENSOR_7 == (n) || TEMP_SENSOR_BED == (n) || TEMP_SENSOR_PROBE == (n) || TEMP_SENSOR_CHAMBER == (n) || TEMP_SENSOR_COOLER == (n))
-
+#define ANY_TEMP_SENSOR_IS(n) ( \
+     n == TEMP_SENSOR_0 || n == TEMP_SENSOR_1 || n == TEMP_SENSOR_2 || n == TEMP_SENSOR_3 \
+  || n == TEMP_SENSOR_4 || n == TEMP_SENSOR_5 || n == TEMP_SENSOR_6 || n == TEMP_SENSOR_7 \
+  || n == TEMP_SENSOR_BED \
+  || n == TEMP_SENSOR_PROBE \
+  || n == TEMP_SENSOR_CHAMBER \
+  || n == TEMP_SENSOR_COOLER \
+  || n == TEMP_SENSOR_REDUNDANT )
 #if ANY_TEMP_SENSOR_IS(1000)
   #define HAS_USER_THERMISTORS 1
 #endif
+#undef ANY_TEMP_SENSOR_IS
+
+// Usurp a sensor to do redundant readings
+#if TEMP_SENSOR_REDUNDANT && !PIN_EXISTS(TEMP_REDUNDANT)
+  #if TEMP_SENSOR_REDUNDANT_SOURCE == -5
+    #if !PIN_EXISTS(TEMP_COOLER)
+      #error "TEMP_SENSOR_REDUNDANT_SOURCE set to COOLER requires TEMP_COOLER_PIN."
+    #else
+      #define TEMP_REDUNDANT_PIN TEMP_COOLER_PIN
+    #endif
+  #elif TEMP_SENSOR_REDUNDANT_SOURCE == -4
+    #if !PIN_EXISTS(TEMP_PROBE)
+      #error "TEMP_SENSOR_REDUNDANT_SOURCE set to PROBE requires TEMP_PROBE_PIN."
+    #else
+      #define TEMP_REDUNDANT_PIN TEMP_PROBE_PIN
+    #endif
+  #elif TEMP_SENSOR_REDUNDANT_SOURCE == -2
+    #if !PIN_EXISTS(TEMP_CHAMBER)
+      #error "TEMP_SENSOR_REDUNDANT_SOURCE set to CHAMBER requires TEMP_CHAMBER_PIN."
+    #else
+      #define TEMP_REDUNDANT_PIN TEMP_CHAMBER_PIN
+    #endif
+  #elif TEMP_SENSOR_REDUNDANT_SOURCE == -1
+    #if !PIN_EXISTS(TEMP_BED)
+      #error "TEMP_SENSOR_REDUNDANT_SOURCE set to BED requires TEMP_BED_PIN."
+    #else
+      #define TEMP_REDUNDANT_PIN TEMP_BED_PIN
+    #endif
+  #elif TEMP_SENSOR_REDUNDANT_SOURCE == 0
+    #if !PIN_EXISTS(TEMP_0)
+      #error "TEMP_SENSOR_REDUNDANT_SOURCE set to 0 requires TEMP_0_PIN."
+    #else
+      #define TEMP_REDUNDANT_PIN TEMP_0_PIN
+    #endif
+  #elif TEMP_SENSOR_REDUNDANT_SOURCE == 1
+    #if !PIN_EXISTS(TEMP_1)
+      #error "TEMP_SENSOR_REDUNDANT_SOURCE set to 1 requires TEMP_1_PIN."
+    #else
+      #define TEMP_REDUNDANT_PIN TEMP_1_PIN
+    #endif
+  #elif TEMP_SENSOR_REDUNDANT_SOURCE == 2
+    #if !PIN_EXISTS(TEMP_2)
+      #error "TEMP_SENSOR_REDUNDANT_SOURCE set to 2 requires TEMP_2_PIN."
+    #else
+      #define TEMP_REDUNDANT_PIN TEMP_2_PIN
+    #endif
+  #elif TEMP_SENSOR_REDUNDANT_SOURCE == 3
+    #if !PIN_EXISTS(TEMP_3)
+      #error "TEMP_SENSOR_REDUNDANT_SOURCE set to 3 requires TEMP_3_PIN."
+    #else
+      #define TEMP_REDUNDANT_PIN TEMP_3_PIN
+    #endif
+  #elif TEMP_SENSOR_REDUNDANT_SOURCE == 4
+    #if !PIN_EXISTS(TEMP_4)
+      #error "TEMP_SENSOR_REDUNDANT_SOURCE set to 4 requires TEMP_4_PIN."
+    #else
+      #define TEMP_REDUNDANT_PIN TEMP_4_PIN
+    #endif
+  #elif TEMP_SENSOR_REDUNDANT_SOURCE == 5
+    #if !PIN_EXISTS(TEMP_5)
+      #error "TEMP_SENSOR_REDUNDANT_SOURCE set to 5 requires TEMP_5_PIN."
+    #else
+      #define TEMP_REDUNDANT_PIN TEMP_5_PIN
+    #endif
+  #elif TEMP_SENSOR_REDUNDANT_SOURCE == 6
+    #if !PIN_EXISTS(TEMP_6)
+      #error "TEMP_SENSOR_REDUNDANT_SOURCE set to 6 requires TEMP_6_PIN."
+    #else
+      #define TEMP_REDUNDANT_PIN TEMP_6_PIN
+    #endif
+  #elif TEMP_SENSOR_REDUNDANT_SOURCE == 7
+    #if !PIN_EXISTS(TEMP_7)
+      #error "TEMP_SENSOR_REDUNDANT_SOURCE set to 7 requires TEMP_7_PIN."
+    #else
+      #define TEMP_REDUNDANT_PIN TEMP_7_PIN
+    #endif
+  #endif
+
+  #ifndef TEMP_SENSOR_REDUNDANT_MAX_DIFF
+    #define TEMP_SENSOR_REDUNDANT_MAX_DIFF 10
+  #endif
+#endif
 
 #if TEMP_SENSOR_0 == -5 || TEMP_SENSOR_0 == -3 || TEMP_SENSOR_0 == -2
   #define TEMP_SENSOR_0_IS_MAX_TC 1
 #elif TEMP_SENSOR_0 == -1
   #define TEMP_SENSOR_0_IS_AD595 1
 #elif TEMP_SENSOR_0 > 0
-  #define TEMP_SENSOR_0_THERMISTOR_ID TEMP_SENSOR_0
   #define TEMP_SENSOR_0_IS_THERMISTOR 1
   #if TEMP_SENSOR_0 == 1000
     #define TEMP_SENSOR_0_IS_CUSTOM 1
 #elif TEMP_SENSOR_1 == -1
   #define TEMP_SENSOR_1_IS_AD595 1
 #elif TEMP_SENSOR_1 > 0
-  #define TEMP_SENSOR_1_THERMISTOR_ID TEMP_SENSOR_1
   #define TEMP_SENSOR_1_IS_THERMISTOR 1
   #if TEMP_SENSOR_1 == 1000
     #define TEMP_SENSOR_1_IS_CUSTOM 1
   #undef HEATER_1_MAXTEMP
 #endif
 
-#if TEMP_SENSOR_0_IS_MAX31855 || TEMP_SENSOR_1_IS_MAX31855
+#if TEMP_SENSOR_REDUNDANT == -5 || TEMP_SENSOR_REDUNDANT == -3 || TEMP_SENSOR_REDUNDANT == -2
+  #define TEMP_SENSOR_REDUNDANT_IS_MAX_TC 1
+  #define HAS_MAX_TC 1
+  #if TEMP_SENSOR_REDUNDANT == -3
+    #define TEMP_SENSOR_REDUNDANT_MAX_TC_TMIN -270
+    #define TEMP_SENSOR_REDUNDANT_MAX_TC_TMAX 1800
+  #else
+    #define TEMP_SENSOR_REDUNDANT_MAX_TC_TMIN    0
+    #define TEMP_SENSOR_REDUNDANT_MAX_TC_TMAX 1024
+  #endif
+  #if TEMP_SENSOR_REDUNDANT_SOURCE == 0
+    #define TEMP_SENSOR_0_MAX_TC_TMIN TEMP_SENSOR_REDUNDANT_MAX_TC_TMIN
+    #define TEMP_SENSOR_0_MAX_TC_TMAX TEMP_SENSOR_REDUNDANT_MAX_TC_TMAX
+  #elif TEMP_SENSOR_REDUNDANT_SOURCE == 1
+    #define TEMP_SENSOR_1_MAX_TC_TMIN TEMP_SENSOR_REDUNDANT_MAX_TC_TMIN
+    #define TEMP_SENSOR_1_MAX_TC_TMAX TEMP_SENSOR_REDUNDANT_MAX_TC_TMAX
+  #endif
+  #if TEMP_SENSOR_REDUNDANT == -5
+    #if TEMP_SENSOR_REDUNDANT_SOURCE != 0 && TEMP_SENSOR_REDUNDANT_SOURCE != 1
+      #error "MAX31865 Thermocouples (-5) not supported for TEMP_SENSOR_REDUNDANT_SOURCE other than TEMP_SENSOR_0/TEMP_SENSOR_1 (0/1)."
+    #endif
+    #define TEMP_SENSOR_REDUNDANT_IS_MAX31865 1
+  #elif TEMP_SENSOR_REDUNDANT == -3
+    #if TEMP_SENSOR_REDUNDANT_SOURCE != 0 && TEMP_SENSOR_REDUNDANT_SOURCE != 1
+      #error "MAX31855 Thermocouples (-3) not supported for TEMP_SENSOR_REDUNDANT_SOURCE other than TEMP_SENSOR_0/TEMP_SENSOR_1 (0/1)."
+    #endif
+    #define TEMP_SENSOR_REDUNDANT_IS_MAX31855 1
+  #elif TEMP_SENSOR_REDUNDANT == -2
+    #if TEMP_SENSOR_REDUNDANT_SOURCE != 0 && TEMP_SENSOR_REDUNDANT_SOURCE != 1
+      #error "MAX6675 Thermocouples (-2) not supported for TEMP_SENSOR_REDUNDANT_SOURCE other than TEMP_SENSOR_0/TEMP_SENSOR_1 (0/1)."
+    #endif
+    #define TEMP_SENSOR_REDUNDANT_IS_MAX6675 1
+  #endif
+  #if (TEMP_SENSOR_0_IS_MAX_TC && TEMP_SENSOR_REDUNDANT != TEMP_SENSOR_0) || (TEMP_SENSOR_1_IS_MAX_TC && TEMP_SENSOR_REDUNDANT != TEMP_SENSOR_1)
+    #if   TEMP_SENSOR_REDUNDANT == -5
+      #error "If MAX31865 Thermocouple (-5) is used for TEMP_SENSOR_0/TEMP_SENSOR_1 then TEMP_SENSOR_REDUNDANT must match."
+    #elif TEMP_SENSOR_REDUNDANT == -3
+      #error "If MAX31855 Thermocouple (-3) is used for TEMP_SENSOR_0/TEMP_SENSOR_1 then TEMP_SENSOR_REDUNDANT must match."
+    #elif TEMP_SENSOR_REDUNDANT == -2
+      #error "If MAX6675 Thermocouple (-2) is used for TEMP_SENSOR_0/TEMP_SENSOR_1 then TEMP_SENSOR_REDUNDANT must match."
+    #endif
+  #endif
+#elif TEMP_SENSOR_REDUNDANT == -4
+  #define TEMP_SENSOR_REDUNDANT_IS_AD8495 1
+#elif TEMP_SENSOR_REDUNDANT == -1
+  #define TEMP_SENSOR_REDUNDANT_IS_AD595 1
+#elif TEMP_SENSOR_REDUNDANT > 0
+  #define TEMP_SENSOR_REDUNDANT_IS_THERMISTOR 1
+  #if TEMP_SENSOR_REDUNDANT == 1000
+    #define TEMP_SENSOR_REDUNDANT_IS_CUSTOM 1
+  #elif TEMP_SENSOR_REDUNDANT == 998 || TEMP_SENSOR_REDUNDANT == 999
+    #error "Dummy sensors are not supported for TEMP_SENSOR_REDUNDANT."
+  #endif
+#endif
+
+#if TEMP_SENSOR_0_IS_MAX31855 || TEMP_SENSOR_1_IS_MAX31855 || TEMP_SENSOR_REDUNDANT_IS_MAX31855
   #define HAS_MAX31855 1
 #endif
-#if TEMP_SENSOR_0_IS_MAX31865 || TEMP_SENSOR_1_IS_MAX31865
+#if TEMP_SENSOR_0_IS_MAX31865 || TEMP_SENSOR_1_IS_MAX31865 || TEMP_SENSOR_REDUNDANT_IS_MAX31865
   #define HAS_MAX31865 1
 #endif
-#if TEMP_SENSOR_0_IS_MAX6675 || TEMP_SENSOR_1_IS_MAX6675
+#if TEMP_SENSOR_0_IS_MAX6675 || TEMP_SENSOR_1_IS_MAX6675 || TEMP_SENSOR_REDUNDANT_IS_MAX6675
   #define HAS_MAX6675 1
 #endif
 
 //
 // Compatibility layer for MAX (SPI) temp boards
 //
+#define TEMP_SENSOR_IS_MAX(n, M) (ENABLED(TEMP_SENSOR_##n##_IS_##M) || (ENABLED(TEMP_SENSOR_REDUNDANT_IS_##M) && TEMP_SENSOR_REDUNDANT_SOURCE == (n)))
+
 #if PIN_EXISTS(MAX6675_SS)
-  #if TEMP_SENSOR_0_IS_MAX31855
+  #if TEMP_SENSOR_IS_MAX(0, MAX31855)
     #define MAX31855_CS_PIN MAX6675_SS_PIN
-  #elif TEMP_SENSOR_0_IS_MAX31865
+  #elif TEMP_SENSOR_IS_MAX(0, MAX31865)
     #define MAX31865_CS_PIN MAX6675_SS_PIN
-  #elif TEMP_SENSOR_0_IS_MAX6675
+  #elif TEMP_SENSOR_IS_MAX(0, MAX6675)
     #define MAX6675_CS_PIN MAX6675_SS_PIN
   #endif
 #endif
 
 #if PIN_EXISTS(MAX6675_SS2)
-  #if TEMP_SENSOR_1_IS_MAX31855
+  #if TEMP_SENSOR_IS_MAX(1, MAX31855)
     #define MAX31855_CS2_PIN MAX6675_SS2_PIN
-  #elif TEMP_SENSOR_1_IS_MAX31865
+  #elif TEMP_SENSOR_IS_MAX(1, MAX31865)
     #define MAX31865_CS2_PIN MAX6675_SS2_PIN
-  #elif TEMP_SENSOR_1_IS_MAX6675
+  #elif TEMP_SENSOR_IS_MAX(1, MAX6675)
     #define MAX6675_CS2_PIN MAX6675_SS2_PIN
   #endif
 #endif
 #elif TEMP_SENSOR_2 == -1
   #define TEMP_SENSOR_2_IS_AD595 1
 #elif TEMP_SENSOR_2 > 0
-  #define TEMP_SENSOR_2_THERMISTOR_ID TEMP_SENSOR_2
   #define TEMP_SENSOR_2_IS_THERMISTOR 1
   #if TEMP_SENSOR_2 == 1000
     #define TEMP_SENSOR_2_IS_CUSTOM 1
 #elif TEMP_SENSOR_3 == -1
   #define TEMP_SENSOR_3_IS_AD595 1
 #elif TEMP_SENSOR_3 > 0
-  #define TEMP_SENSOR_3_THERMISTOR_ID TEMP_SENSOR_3
   #define TEMP_SENSOR_3_IS_THERMISTOR 1
   #if TEMP_SENSOR_3 == 1000
     #define TEMP_SENSOR_3_IS_CUSTOM 1
 #elif TEMP_SENSOR_4 == -1
   #define TEMP_SENSOR_4_IS_AD595 1
 #elif TEMP_SENSOR_4 > 0
-  #define TEMP_SENSOR_4_THERMISTOR_ID TEMP_SENSOR_4
   #define TEMP_SENSOR_4_IS_THERMISTOR 1
   #if TEMP_SENSOR_4 == 1000
     #define TEMP_SENSOR_4_IS_CUSTOM 1
 #elif TEMP_SENSOR_5 == -1
   #define TEMP_SENSOR_5_IS_AD595 1
 #elif TEMP_SENSOR_5 > 0
-  #define TEMP_SENSOR_5_THERMISTOR_ID TEMP_SENSOR_5
   #define TEMP_SENSOR_5_IS_THERMISTOR 1
   #if TEMP_SENSOR_5 == 1000
     #define TEMP_SENSOR_5_IS_CUSTOM 1
 #elif TEMP_SENSOR_6 == -1
   #define TEMP_SENSOR_6_IS_AD595 1
 #elif TEMP_SENSOR_6 > 0
-  #define TEMP_SENSOR_6_THERMISTOR_ID TEMP_SENSOR_6
   #define TEMP_SENSOR_6_IS_THERMISTOR 1
   #if TEMP_SENSOR_6 == 1000
     #define TEMP_SENSOR_6_IS_CUSTOM 1
 #elif TEMP_SENSOR_7 == -1
   #define TEMP_SENSOR_7_IS_AD595 1
 #elif TEMP_SENSOR_7 > 0
-  #define TEMP_SENSOR_7_THERMISTOR_ID TEMP_SENSOR_7
   #define TEMP_SENSOR_7_IS_THERMISTOR 1
   #if TEMP_SENSOR_7 == 1000
     #define TEMP_SENSOR_7_IS_CUSTOM 1
 #elif TEMP_SENSOR_BED == -1
   #define TEMP_SENSOR_BED_IS_AD595 1
 #elif TEMP_SENSOR_BED > 0
-  #define TEMP_SENSOR_BED_THERMISTOR_ID TEMP_SENSOR_BED
   #define TEMP_SENSOR_BED_IS_THERMISTOR 1
   #if TEMP_SENSOR_BED == 1000
     #define TEMP_SENSOR_BED_IS_CUSTOM 1
 #elif TEMP_SENSOR_CHAMBER == -1
   #define TEMP_SENSOR_CHAMBER_IS_AD595 1
 #elif TEMP_SENSOR_CHAMBER > 0
-  #define TEMP_SENSOR_CHAMBER_THERMISTOR_ID TEMP_SENSOR_CHAMBER
   #define TEMP_SENSOR_CHAMBER_IS_THERMISTOR 1
   #if TEMP_SENSOR_CHAMBER == 1000
     #define TEMP_SENSOR_CHAMBER_IS_CUSTOM 1
 #endif
 
 #if TEMP_SENSOR_COOLER == -4
-  #define COOLER_USES_AD8495 1
+  #define TEMP_SENSOR_COOLER_IS_AD8495 1
 #elif TEMP_SENSOR_COOLER == -3
   #error "MAX31855 Thermocouples (-3) not supported for TEMP_SENSOR_COOLER."
 #elif TEMP_SENSOR_COOLER == -2
   #error "MAX6675 Thermocouples (-2) not supported for TEMP_SENSOR_COOLER."
 #elif TEMP_SENSOR_COOLER == -1
-  #define COOLER_USES_AD595 1
+  #define TEMP_SENSOR_COOLER_IS_AD595 1
 #elif TEMP_SENSOR_COOLER > 0
-  #define TEMP_SENSOR_COOLER_THERMISTOR_ID TEMP_SENSOR_COOLER
   #define TEMP_SENSOR_COOLER_IS_THERMISTOR 1
   #if TEMP_SENSOR_COOLER == 1000
-    #define COOLER_USER_THERMISTOR 1
+    #define TEMP_SENSOR_COOLER_IS_CUSTOM 1
   #elif TEMP_SENSOR_COOLER == 998 || TEMP_SENSOR_COOLER == 999
-    #define COOLER_DUMMY_THERMISTOR 1
+    #define TEMP_SENSOR_COOLER_IS_DUMMY 1
   #endif
 #else
   #undef COOLER_MINTEMP
 #elif TEMP_SENSOR_PROBE == -1
   #define TEMP_SENSOR_PROBE_IS_AD595 1
 #elif TEMP_SENSOR_PROBE > 0
-  #define TEMP_SENSOR_PROBE_THERMISTOR_ID TEMP_SENSOR_PROBE
   #define TEMP_SENSOR_PROBE_IS_THERMISTOR 1
   #if TEMP_SENSOR_PROBE == 1000
     #define TEMP_SENSOR_PROBE_IS_CUSTOM 1
 #if HAS_ADC_TEST(COOLER)
   #define HAS_TEMP_ADC_COOLER 1
 #endif
+#if HAS_ADC_TEST(REDUNDANT)
+  #define HAS_TEMP_ADC_REDUNDANT 1
+#endif
 
 #define HAS_TEMP(N) ANY(HAS_TEMP_ADC_##N, TEMP_SENSOR_##N##_IS_MAX_TC, TEMP_SENSOR_##N##_IS_DUMMY)
 #if HAS_HOTEND && HAS_TEMP(0)
 #if HAS_TEMP(COOLER)
   #define HAS_TEMP_COOLER 1
 #endif
+#if HAS_TEMP(REDUNDANT)
+  #define HAS_TEMP_REDUNDANT 1
+#endif
 
 #if ENABLED(JOYSTICK)
   #if PIN_EXISTS(JOY_X)

Marlin/src/inc/SanityCheck.h

   #error "MKS_LCD12864 is now MKS_LCD12864A or MKS_LCD12864B."
 #elif defined(NEOPIXEL_BKGD_LED_INDEX)
   #error "NEOPIXEL_BKGD_LED_INDEX is now NEOPIXEL_BKGD_INDEX_FIRST."
+#elif defined(TEMP_SENSOR_1_AS_REDUNDANT)
+  #error "TEMP_SENSOR_1_AS_REDUNDANT is now TEMP_SENSOR_REDUNDANT, with associated TEMP_SENSOR_REDUNDANT_* config."
+#elif defined(MAX_REDUNDANT_TEMP_SENSOR_DIFF)
+  #error "MAX_REDUNDANT_TEMP_SENSOR_DIFF is now TEMP_SENSOR_REDUNDANT_MAX_DIFF"
 #endif
 
 constexpr float arm[] = AXIS_RELATIVE_MODES;
   #error "TEMP_SENSOR_CHAMBER 1000 requires CHAMBER_PULLUP_RESISTOR_OHMS, CHAMBER_RESISTANCE_25C_OHMS and CHAMBER_BETA in Configuration_adv.h."
 #elif TEMP_SENSOR_PROBE_IS_CUSTOM && !(defined(PROBE_PULLUP_RESISTOR_OHMS) && defined(PROBE_RESISTANCE_25C_OHMS) && defined(PROBE_BETA))
   #error "TEMP_SENSOR_PROBE 1000 requires PROBE_PULLUP_RESISTOR_OHMS, PROBE_RESISTANCE_25C_OHMS and PROBE_BETA in Configuration_adv.h."
+#elif TEMP_SENSOR_REDUNDANT_IS_CUSTOM && !(defined(REDUNDANT_PULLUP_RESISTOR_OHMS) && defined(REDUNDANT_RESISTANCE_25C_OHMS) && defined(REDUNDANT_BETA))
+  #error "TEMP_SENSOR_REDUNDANT 1000 requires REDUNDANT_PULLUP_RESISTOR_OHMS, REDUNDANT_RESISTANCE_25C_OHMS and REDUNDANT_BETA in Configuration_adv.h."
 #endif
 
 /**
  * Pins and Sensor IDs must be set for each heater
  */
 #if TEMP_SENSOR_0_IS_MAX6675 && !ANY_PIN(MAX6675_SS, MAX31855_CS, MAX31865_CS, MAX6675_CS)
-  #error "TEMP_SENSOR_0 requires a MAX6675_SS_PIN, MAX6675_CS_PIN, MAX31855_CS_PIN, or MAX31865_CS_PIN."
+  #error "TEMP_SENSOR_0 -2 requires a MAX6675_SS_PIN, MAX6675_CS_PIN, MAX31855_CS_PIN, or MAX31865_CS_PIN."
 #elif HAS_HOTEND && !HAS_TEMP_HOTEND && !TEMP_SENSOR_0_IS_DUMMY
   #error "TEMP_0_PIN (required for TEMP_SENSOR_0) not defined for this board."
 #elif EITHER(HAS_MULTI_HOTEND, HEATERS_PARALLEL) && !HAS_HEATER_1
   #error "HEATER_1_PIN is not defined. TEMP_SENSOR_1 might not be set, or the board (not EEB / EEF?) doesn't define a pin."
 #endif
 
+/**
+ * Redundant temperature sensor config
+ */
+#if HAS_TEMP_REDUNDANT
+  #if !defined(TEMP_SENSOR_REDUNDANT_SOURCE)
+    #error "TEMP_SENSOR_REDUNDANT requires TEMP_SENSOR_REDUNDANT_SOURCE."
+  #elif !defined(TEMP_SENSOR_REDUNDANT_TARGET)
+    #error "TEMP_SENSOR_REDUNDANT requires TEMP_SENSOR_REDUNDANT_TARGET."
+  #elif TEMP_SENSOR_REDUNDANT_SOURCE == TEMP_SENSOR_REDUNDANT_TARGET
+    #error "TEMP_SENSOR_REDUNDANT_SOURCE can't be the same as TEMP_SENSOR_REDUNDANT_TARGET."
+  #elif TEMP_SENSOR_REDUNDANT_SOURCE < -5 || TEMP_SENSOR_REDUNDANT_SOURCE > 7
+    #error "TEMP_SENSOR_REDUNDANT_SOURCE must be between -5 and 7."
+  #elif TEMP_SENSOR_REDUNDANT_TARGET < -5 || TEMP_SENSOR_REDUNDANT_TARGET > 7
+    #error "TEMP_SENSOR_REDUNDANT_TARGET must be between -5 and 7."
+  #elif TEMP_SENSOR_REDUNDANT_SOURCE == -3
+    #error "TEMP_SENSOR_REDUNDANT_SOURCE can't be -3 (not used)."
+  #elif TEMP_SENSOR_REDUNDANT_TARGET == -3
+    #error "TEMP_SENSOR_REDUNDANT_TARGET can't be -3 (not used)."
+  #elif HAS_MULTI_HOTEND && TEMP_SENSOR_REDUNDANT_SOURCE < HOTENDS
+    #error "TEMP_SENSOR_REDUNDANT_SOURCE must be after the last TEMP_SENSOR used with a hotend; you can't use a sensor in the middle of two hotends."
+  #endif
+
+  #if TEMP_SENSOR_REDUNDANT_SOURCE == 0 && HAS_HOTEND
+    #error "TEMP_SENSOR_REDUNDANT_SOURCE can not be 0 if a hotend is used. E0 always uses TEMP_SENSOR_0."
+  #elif TEMP_SENSOR_REDUNDANT_SOURCE == -5 && HAS_TEMP_COOLER
+    #error "TEMP_SENSOR_REDUNDANT_SOURCE can't be Cooler (-5): TEMP_SENSOR_COOLER has already defined the sensor."
+  #elif TEMP_SENSOR_REDUNDANT_SOURCE == -4 && HAS_TEMP_PROBE
+    #error "TEMP_SENSOR_REDUNDANT_SOURCE can't be Probe (-4): TEMP_SENSOR_PROBE has already defined the sensor."
+  #elif TEMP_SENSOR_REDUNDANT_SOURCE == -2 && HAS_TEMP_CHAMBER
+    #error "TEMP_SENSOR_REDUNDANT_SOURCE can't be Chamber (-2): TEMP_SENSOR_CHAMBER has already defined the sensor."
+  #elif TEMP_SENSOR_REDUNDANT_SOURCE == -1 && HAS_TEMP_BED
+    #error "TEMP_SENSOR_REDUNDANT_SOURCE can't be Bed (-1): TEMP_SENSOR_BED has already defined the sensor."
+  #endif
+
+  #if TEMP_SENSOR_REDUNDANT_TARGET == 0 && !PIN_EXISTS(TEMP_0)
+    #error "TEMP_SENSOR_REDUNDANT_TARGET can't be E0 (0): requires TEMP_0_PIN"
+  #elif TEMP_SENSOR_REDUNDANT_TARGET == 1 && !PIN_EXISTS(TEMP_1)
+    #error "TEMP_SENSOR_REDUNDANT_TARGET can't be E1 (1): requires TEMP_1_PIN"
+  #elif TEMP_SENSOR_REDUNDANT_TARGET == 2 && !PIN_EXISTS(TEMP_2)
+    #error "TEMP_SENSOR_REDUNDANT_TARGET can't be E2 (2): requires TEMP_2_PIN"
+  #elif TEMP_SENSOR_REDUNDANT_TARGET == 3 && !PIN_EXISTS(TEMP_3)
+    #error "TEMP_SENSOR_REDUNDANT_TARGET can't be E3 (3): requires TEMP_3_PIN"
+  #elif TEMP_SENSOR_REDUNDANT_TARGET == 4 && !PIN_EXISTS(TEMP_4)
+    #error "TEMP_SENSOR_REDUNDANT_TARGET can't be E4 (4): requires TEMP_4_PIN"
+  #elif TEMP_SENSOR_REDUNDANT_TARGET == 5 && !PIN_EXISTS(TEMP_5)
+    #error "TEMP_SENSOR_REDUNDANT_TARGET can't be E5 (5): requires TEMP_5_PIN"
+  #elif TEMP_SENSOR_REDUNDANT_TARGET == 6 && !PIN_EXISTS(TEMP_6)
+    #error "TEMP_SENSOR_REDUNDANT_TARGET can't be E6 (6): requires TEMP_6_PIN"
+  #elif TEMP_SENSOR_REDUNDANT_TARGET == 7 && !PIN_EXISTS(TEMP_7)
+    #error "TEMP_SENSOR_REDUNDANT_TARGET can't be E7 (7): requires TEMP_7_PIN"
+  #elif TEMP_SENSOR_REDUNDANT_TARGET == -1 && !PIN_EXISTS(TEMP_BED)
+    #error "TEMP_SENSOR_REDUNDANT_TARGET can't be Bed (-1): requires TEMP_BED_PIN"
+  #elif TEMP_SENSOR_REDUNDANT_TARGET == -2 && !PIN_EXISTS(TEMP_CHAMBER)
+    #error "TEMP_SENSOR_REDUNDANT_TARGET can't be Chamber (-2): requires TEMP_CHAMBER_PIN"
+  #elif TEMP_SENSOR_REDUNDANT_TARGET == -4 && !PIN_EXISTS(TEMP_PROBE)
+    #error "TEMP_SENSOR_REDUNDANT_TARGET can't be Probe (-4): requires TEMP_PROBE_PIN"
+  #elif TEMP_SENSOR_REDUNDANT_TARGET == -5 && !PIN_EXISTS(TEMP_COOLER)
+    #error "TEMP_SENSOR_REDUNDANT_TARGET can't be Cooler (-5): requires TEMP_COOLER_PIN"
+  #endif
+
+  #if TEMP_SENSOR_REDUNDANT_IS_MAX_TC && TEMP_SENSOR_REDUNDANT_SOURCE == 0 && !PIN_EXISTS(MAX6675_SS)
+    #error "TEMP_SENSOR_REDUNDANT MAX Thermocouple with TEMP_SENSOR_REDUNDANT_SOURCE 0 requires a MAX6675_SS_PIN, MAX6675_CS_PIN, MAX31855_CS_PIN, or MAX31865_CS_PIN."
+  #elif TEMP_SENSOR_REDUNDANT_IS_MAX_TC && TEMP_SENSOR_REDUNDANT_SOURCE == 1 && !PIN_EXISTS(MAX6675_SS2)
+    #error "TEMP_SENSOR_REDUNDANT MAX Thermocouple with TEMP_SENSOR_REDUNDANT_SOURCE 1 requires a MAX6675_SS2_PIN, MAX6675_CS_PIN, MAX31855_CS_PIN, or MAX31865_CS_PIN."
+  #endif
+#endif
+
 #if HAS_MULTI_HOTEND
   #if TEMP_SENSOR_1_IS_MAX6675 && !ANY_PIN(MAX6675_SS2, MAX31855_CS2, MAX31865_CS2, MAX6675_CS2)
     #error "TEMP_SENSOR_1 requires a MAX6675_SS2_PIN, MAX6675_CS2_PIN, MAX31855_CS2_PIN, or MAX31865_CS2_PIN."
     #error "TEMP_SENSOR_1 is required with 2 or more HOTENDS."
   #elif !ANY_PIN(TEMP_1, MAX6675_SS2) && !TEMP_SENSOR_1_IS_DUMMY
     #error "TEMP_1_PIN or MAX6675_SS2_PIN not defined for this board."
-  #elif ENABLED(TEMP_SENSOR_1_AS_REDUNDANT)
-    #error "HOTENDS must be 1 with TEMP_SENSOR_1_AS_REDUNDANT."
   #endif
   #if HOTENDS > 2
     #if TEMP_SENSOR_2 == 0
   #elif TEMP_SENSOR_7 != 0
     #error "TEMP_SENSOR_7 shouldn't be set with only 2 HOTENDS."
   #endif
-#elif TEMP_SENSOR_1 != 0 && DISABLED(TEMP_SENSOR_1_AS_REDUNDANT)
+#elif TEMP_SENSOR_1 != 0
   #error "TEMP_SENSOR_1 shouldn't be set with only 1 HOTEND."
 #elif TEMP_SENSOR_2 != 0
   #error "TEMP_SENSOR_2 shouldn't be set with only 1 HOTEND."
   #endif
 #endif
 
-#if ENABLED(TEMP_SENSOR_1_AS_REDUNDANT) && TEMP_SENSOR_1 == 0
-  #error "TEMP_SENSOR_1 is required with TEMP_SENSOR_1_AS_REDUNDANT."
-#endif
-
-#if TEMP_SENSOR_0_IS_MAX31865 && !(defined(MAX31865_SENSOR_OHMS_0) && defined(MAX31865_CALIBRATION_OHMS_0))
-  #error "MAX31865_SENSOR_OHMS_0 and MAX31865_CALIBRATION_OHMS_0 must be set if TEMP_SENSOR_0 is MAX31865."
-#elif TEMP_SENSOR_1_IS_MAX31865 && !(defined(MAX31865_SENSOR_OHMS_1) && defined(MAX31865_CALIBRATION_OHMS_1))
-  #error "MAX31865_SENSOR_OHMS_1 and MAX31865_CALIBRATION_OHMS_1 must be set if TEMP_SENSOR_1 is MAX31865."
+#if TEMP_SENSOR_IS_MAX(0, MAX31865) && !(defined(MAX31865_SENSOR_OHMS_0) && defined(MAX31865_CALIBRATION_OHMS_0))
+  #error "MAX31865_SENSOR_OHMS_0 and MAX31865_CALIBRATION_OHMS_0 must be set if TEMP_SENSOR_0/TEMP_SENSOR_REDUNDANT is MAX31865."
+#elif TEMP_SENSOR_IS_MAX(1, MAX31865) && !(defined(MAX31865_SENSOR_OHMS_1) && defined(MAX31865_CALIBRATION_OHMS_1))
+  #error "MAX31865_SENSOR_OHMS_1 and MAX31865_CALIBRATION_OHMS_1 must be set if TEMP_SENSOR_1/TEMP_SENSOR_REDUNDANT is MAX31865."
 #endif
 
 /**

Marlin/src/module/temperature.cpp

   #include "../feature/host_actions.h"
 #endif
 
+#define TEMP_SENSOR_IS_ANY_MAX_TC(n) (ENABLED(TEMP_SENSOR_##n##_IS_MAX_TC) || (ENABLED(TEMP_SENSOR_REDUNDANT_IS_MAX_TC) && ENABLED(TEMP_SENSOR_REDUNDANT_SOURCE) && TEMP_SENSOR_REDUNDANT_SOURCE == n))
+
 // LIB_MAX31855 can be added to the build_flags in platformio.ini to use a user-defined library
 #if LIB_USR_MAX31855
   #include <Adafruit_MAX31855.h>
   #if PIN_EXISTS(MAX31855_MISO) && PIN_EXISTS(MAX31855_SCK)
     #define MAX31855_USES_SW_SPI 1
   #endif
-  #if TEMP_SENSOR_0_IS_MAX31855 && PIN_EXISTS(MAX31855_CS)
+  #if TEMP_SENSOR_IS_MAX(0, MAX31855) && PIN_EXISTS(MAX31855_CS)
     #define HAS_MAX31855_TEMP 1
     Adafruit_MAX31855 max31855_0 = Adafruit_MAX31855(MAX31855_CS_PIN
       #if MAX31855_USES_SW_SPI
       #endif
     );
   #endif
-  #if TEMP_SENSOR_1_IS_MAX31855 && PIN_EXISTS(MAX31855_CS2)
+  #if TEMP_SENSOR_IS_MAX(1, MAX31855) && PIN_EXISTS(MAX31855_CS2)
     #define HAS_MAX31855_TEMP 1
     Adafruit_MAX31855 max31855_1 = Adafruit_MAX31855(MAX31855_CS2_PIN
       #if MAX31855_USES_SW_SPI
   #if PIN_EXISTS(MAX31865_MISO) && PIN_EXISTS(MAX31865_SCK)
     #define MAX31865_USES_SW_SPI 1
   #endif
-  #if TEMP_SENSOR_0_IS_MAX31865 && PIN_EXISTS(MAX31865_CS)
+  #if TEMP_SENSOR_IS_MAX(0, MAX31865) && PIN_EXISTS(MAX31865_CS)
     #define HAS_MAX31865_TEMP 1
       Adafruit_MAX31865 max31865_0 = Adafruit_MAX31865(MAX31865_CS_PIN
         #if MAX31865_USES_SW_SPI && PIN_EXISTS(MAX31865_MOSI)
         #endif
       );
   #endif
-  #if TEMP_SENSOR_1_IS_MAX31865 && PIN_EXISTS(MAX31865_CS2)
+  #if TEMP_SENSOR_IS_MAX(1, MAX31865) && PIN_EXISTS(MAX31865_CS2)
     #define HAS_MAX31865_TEMP 1
     Adafruit_MAX31865 max31865_1 = Adafruit_MAX31865(MAX31865_CS2_PIN
       #if MAX31865_USES_SW_SPI && PIN_EXISTS(MAX31865_MOSI)
   #if PIN_EXISTS(MAX6675_MISO) && PIN_EXISTS(MAX6675_SCK)
     #define MAX6675_USES_SW_SPI 1
   #endif
-  #if TEMP_SENSOR_0_IS_MAX6675 && PIN_EXISTS(MAX6675_CS)
+  #if TEMP_SENSOR_IS_MAX(0, MAX6675) && PIN_EXISTS(MAX6675_CS)
     #define HAS_MAX6675_TEMP 1
     MAX6675 max6675_0 = MAX6675(MAX6675_CS_PIN
       #if MAX6675_USES_SW_SPI
       #endif
     );
   #endif
-  #if TEMP_SENSOR_1_IS_MAX6675 && PIN_EXISTS(MAX6675_CS2)
+  #if TEMP_SENSOR_IS_MAX(1, MAX6675) && PIN_EXISTS(MAX6675_CS2)
     #define HAS_MAX6675_TEMP 1
     MAX6675 max6675_1 = MAX6675(MAX6675_CS2_PIN
       #if MAX6675_USES_SW_SPI
   #define NO_THERMO_TEMPS 1
 #endif
 
-#if (TEMP_SENSOR_0_IS_MAX_TC || TEMP_SENSOR_1_IS_MAX_TC) && PINS_EXIST(MAX6675_SCK, MAX6675_DO) && NO_THERMO_TEMPS
+#if (TEMP_SENSOR_0_IS_MAX_TC || TEMP_SENSOR_1_IS_MAX_TC || TEMP_SENSOR_REDUNDANT_IS_MAX_TC) && PINS_EXIST(MAX6675_SCK, MAX6675_DO) && NO_THERMO_TEMPS
   #define THERMO_SEPARATE_SPI 1
 #endif
 
 #endif
 
 #if HAS_HOTEND_THERMISTOR
-  #if ENABLED(TEMP_SENSOR_1_AS_REDUNDANT)
-    static const temp_entry_t* heater_ttbl_map[2] = { TEMPTABLE_0, TEMPTABLE_1 };
-    static constexpr uint8_t heater_ttbllen_map[2] = { TEMPTABLE_0_LEN, TEMPTABLE_1_LEN };
-  #else
-    #define NEXT_TEMPTABLE(N) ,TEMPTABLE_##N
-    #define NEXT_TEMPTABLE_LEN(N) ,TEMPTABLE_##N##_LEN
-    static const temp_entry_t* heater_ttbl_map[HOTENDS] = ARRAY_BY_HOTENDS(TEMPTABLE_0 REPEAT_S(1, HOTENDS, NEXT_TEMPTABLE));
-    static constexpr uint8_t heater_ttbllen_map[HOTENDS] = ARRAY_BY_HOTENDS(TEMPTABLE_0_LEN REPEAT_S(1, HOTENDS, NEXT_TEMPTABLE_LEN));
-  #endif
+  #define NEXT_TEMPTABLE(N) ,TEMPTABLE_##N
+  #define NEXT_TEMPTABLE_LEN(N) ,TEMPTABLE_##N##_LEN
+  static const temp_entry_t* heater_ttbl_map[HOTENDS] = ARRAY_BY_HOTENDS(TEMPTABLE_0 REPEAT_S(1, HOTENDS, NEXT_TEMPTABLE));
+  static constexpr uint8_t heater_ttbllen_map[HOTENDS] = ARRAY_BY_HOTENDS(TEMPTABLE_0_LEN REPEAT_S(1, HOTENDS, NEXT_TEMPTABLE_LEN));
 #endif
 
 Temperature thermalManager;
 
 #if HAS_HOTEND
   hotend_info_t Temperature::temp_hotend[HOTENDS];
-  #if ENABLED(TEMP_SENSOR_1_AS_REDUNDANT)
-    temp_info_t Temperature::temp_redundant;
-  #endif
   #define _HMT(N) HEATER_##N##_MAXTEMP,
   const celsius_t Temperature::hotend_maxtemp[HOTENDS] = ARRAY_BY_HOTENDS(HEATER_0_MAXTEMP, HEATER_1_MAXTEMP, HEATER_2_MAXTEMP, HEATER_3_MAXTEMP, HEATER_4_MAXTEMP, HEATER_5_MAXTEMP, HEATER_6_MAXTEMP, HEATER_7_MAXTEMP);
 #endif
 
+#if HAS_TEMP_REDUNDANT
+  redundant_temp_info_t Temperature::temp_redundant;
+#endif
+
 #if ENABLED(AUTO_POWER_E_FANS)
   uint8_t Temperature::autofan_speed[HOTENDS]; // = { 0 }
 #endif
       if (degHotend(0) < _MAX(HEATER_0_MINTEMP, TEMP_SENSOR_0_MAX_TC_TMIN + .01)) min_temp_error(H_E0);
     #endif
     #if TEMP_SENSOR_1_IS_MAX_TC
-      if (TERN(TEMP_SENSOR_1_AS_REDUNDANT, degHotendRedundant(), degHotend(1)) > _MIN(HEATER_1_MAXTEMP, TEMP_SENSOR_1_MAX_TC_TMAX - 1.0)) max_temp_error(H_E1);
-      if (TERN(TEMP_SENSOR_1_AS_REDUNDANT, degHotendRedundant(), degHotend(1)) < _MAX(HEATER_1_MINTEMP, TEMP_SENSOR_1_MAX_TC_TMIN + .01)) min_temp_error(H_E1);
+      if (degHotend(1) > _MIN(HEATER_1_MAXTEMP, TEMP_SENSOR_1_MAX_TC_TMAX - 1.0)) max_temp_error(H_E1);
+      if (degHotend(1) < _MAX(HEATER_1_MINTEMP, TEMP_SENSOR_1_MAX_TC_TMIN + .01)) min_temp_error(H_E1);
+    #endif
+    #if TEMP_SENSOR_REDUNDANT_IS_MAX_TC
+      if (degRedundant() > TEMP_SENSOR_REDUNDANT_MAX_TC_TMAX - 1.0) max_temp_error(H_REDUNDANT);
+      if (degRedundant() < TEMP_SENSOR_REDUNDANT_MAX_TC_TMIN + .01) min_temp_error(H_REDUNDANT);
     #endif
   #endif
 
         }
       #endif
 
-      #if ENABLED(TEMP_SENSOR_1_AS_REDUNDANT)
-        // Make sure measured temperatures are close together
-        if (ABS(degHotend(0) - degHotendRedundant()) > MAX_REDUNDANT_TEMP_SENSOR_DIFF)
-          _temp_error(H_E0, PSTR(STR_REDUNDANCY), GET_TEXT(MSG_ERR_REDUNDANT_TEMP));
-      #endif
-
     } // HOTEND_LOOP
 
   #endif // HAS_HOTEND
 
+  #if HAS_TEMP_REDUNDANT
+    // Make sure measured temperatures are close together
+    if (ABS(degRedundantTarget() - degRedundant()) > TEMP_SENSOR_REDUNDANT_MAX_DIFF)
+      _temp_error((heater_id_t)TEMP_SENSOR_REDUNDANT_TARGET, PSTR(STR_REDUNDANCY), GET_TEXT(MSG_ERR_REDUNDANT_TEMP));
+  #endif
+
   #if HAS_AUTO_FAN
     if (ELAPSED(ms, next_auto_fan_check_ms)) { // only need to check fan state very infrequently
       checkExtruderAutoFans();
         { true, 0, 0, BED_PULLUP_RESISTOR_OHMS, BED_RESISTANCE_25C_OHMS, 0, 0, BED_BETA, 0 },
       #endif
       #if TEMP_SENSOR_CHAMBER_IS_CUSTOM
-        { true, 0, 0, CHAMBER_PULLUP_RESISTOR_OHMS, CHAMBER_RESISTANCE_25C_OHMS, 0, 0, CHAMBER_BETA, 0 }
+        { true, 0, 0, CHAMBER_PULLUP_RESISTOR_OHMS, CHAMBER_RESISTANCE_25C_OHMS, 0, 0, CHAMBER_BETA, 0 },
       #endif
       #if TEMP_SENSOR_COOLER_IS_CUSTOM
-        { true, 0, 0, COOLER_PULLUP_RESISTOR_OHMS, COOLER_RESISTANCE_25C_OHMS, 0, 0, COOLER_BETA, 0 }
+        { true, 0, 0, COOLER_PULLUP_RESISTOR_OHMS, COOLER_RESISTANCE_25C_OHMS, 0, 0, COOLER_BETA, 0 },
       #endif
       #if TEMP_SENSOR_PROBE_IS_CUSTOM
-        { true, 0, 0, PROBE_PULLUP_RESISTOR_OHMS, PROBE_RESISTANCE_25C_OHMS, 0, 0, PROBE_BETA, 0 }
+        { true, 0, 0, PROBE_PULLUP_RESISTOR_OHMS, PROBE_RESISTANCE_25C_OHMS, 0, 0, PROBE_BETA, 0 },
+      #endif
+      #if TEMP_SENSOR_REDUNDANT_IS_CUSTOM
+        { true, 0, 0, REDUNDANT_PULLUP_RESISTOR_OHMS, REDUNDANT_RESISTANCE_25C_OHMS, 0, 0, REDUNDANT_BETA, 0 },
       #endif
     };
     COPY(user_thermistor, default_user_thermistor);
       TERN_(TEMP_SENSOR_CHAMBER_IS_CUSTOM, t_index == CTI_CHAMBER ? PSTR("CHAMBER") :)
       TERN_(TEMP_SENSOR_COOLER_IS_CUSTOM, t_index == CTI_COOLER ? PSTR("COOLER") :)
       TERN_(TEMP_SENSOR_PROBE_IS_CUSTOM, t_index == CTI_PROBE ? PSTR("PROBE") :)
+      TERN_(TEMP_SENSOR_REDUNDANT_IS_CUSTOM, t_index == CTI_REDUNDANT ? PSTR("REDUNDANT") :)
       nullptr
     );
     SERIAL_EOL();
   // Derived from RepRap FiveD extruder::getTemperature()
   // For hot end temperature measurement.
   celsius_float_t Temperature::analog_to_celsius_hotend(const int16_t raw, const uint8_t e) {
-      if (e >= HOTENDS + ENABLED(TEMP_SENSOR_1_AS_REDUNDANT)) {
+      if (e >= HOTENDS) {
         SERIAL_ERROR_START();
         SERIAL_ECHO(e);
         SERIAL_ECHOLNPGM(STR_INVALID_EXTRUDER_NUM);
   }
 #endif // HAS_TEMP_PROBE
 
+#if HAS_TEMP_REDUNDANT
+  // For redundant temperature measurement.
+  celsius_float_t Temperature::analog_to_celsius_redundant(const int16_t raw) {
+    #if TEMP_SENSOR_REDUNDANT_IS_CUSTOM
+      return user_thermistor_to_deg_c(CTI_REDUNDANT, raw);
+    #elif TEMP_SENSOR_REDUNDANT_IS_MAX_TC && TEMP_SENSOR_REDUNDANT_SOURCE == 0
+      return TERN(TEMP_SENSOR_REDUNDANT_IS_MAX31865, max31865_0.temperature(MAX31865_SENSOR_OHMS_0, MAX31865_CALIBRATION_OHMS_0), raw * 0.25);
+    #elif TEMP_SENSOR_REDUNDANT_IS_MAX_TC && TEMP_SENSOR_REDUNDANT_SOURCE == 1
+      return TERN(TEMP_SENSOR_REDUNDANT_IS_MAX31865, max31865_1.temperature(MAX31865_SENSOR_OHMS_1, MAX31865_CALIBRATION_OHMS_1), raw * 0.25);
+    #elif TEMP_SENSOR_REDUNDANT_IS_THERMISTOR
+      SCAN_THERMISTOR_TABLE(TEMPTABLE_REDUNDANT, TEMPTABLE_REDUNDANT_LEN);
+    #elif TEMP_SENSOR_REDUNDANT_IS_AD595
+      return TEMP_AD595(raw);
+    #elif TEMP_SENSOR_REDUNDANT_IS_AD8495
+      return TEMP_AD8495(raw);
+    #else
+      UNUSED(raw);
+      return 0;
+    #endif
+  }
+#endif // HAS_TEMP_REDUNDANT
+
 /**
  * Convert the raw sensor readings into actual Celsius temperatures and
  * validate raw temperatures. Bad readings generate min/maxtemp errors.
   watchdog_refresh(); // Reset because raw_temps_ready was set by the interrupt
 
   TERN_(TEMP_SENSOR_0_IS_MAX_TC, temp_hotend[0].raw = READ_MAX_TC(0));
-  TERN_(TEMP_SENSOR_1_IS_MAX_TC, TERN(TEMP_SENSOR_1_AS_REDUNDANT, temp_redundant, temp_hotend[1]).raw = READ_MAX_TC(1));
+  TERN_(TEMP_SENSOR_1_IS_MAX_TC, temp_hotend[1].raw = READ_MAX_TC(1));
+  TERN_(TEMP_SENSOR_REDUNDANT_IS_MAX_TC, temp_redundant.raw = READ_MAX_TC(TEMP_SENSOR_REDUNDANT_SOURCE));
   #if HAS_HOTEND
     HOTEND_LOOP() temp_hotend[e].celsius = analog_to_celsius_hotend(temp_hotend[e].raw, e);
   #endif
-  TERN_(TEMP_SENSOR_1_AS_REDUNDANT, temp_redundant.celsius = analog_to_celsius_hotend(temp_redundant.raw, 1));
 
-  TERN_(HAS_HEATED_BED,   temp_bed.celsius     = analog_to_celsius_bed(temp_bed.raw));
-  TERN_(HAS_TEMP_CHAMBER, temp_chamber.celsius = analog_to_celsius_chamber(temp_chamber.raw));
-  TERN_(HAS_TEMP_COOLER,  temp_cooler.celsius  = analog_to_celsius_cooler(temp_cooler.raw));
-  TERN_(HAS_TEMP_PROBE,   temp_probe.celsius   = analog_to_celsius_probe(temp_probe.raw));
+  TERN_(HAS_HEATED_BED,     temp_bed.celsius       = analog_to_celsius_bed(temp_bed.raw));
+  TERN_(HAS_TEMP_CHAMBER,   temp_chamber.celsius   = analog_to_celsius_chamber(temp_chamber.raw));
+  TERN_(HAS_TEMP_COOLER,    temp_cooler.celsius    = analog_to_celsius_cooler(temp_cooler.raw));
+  TERN_(HAS_TEMP_PROBE,     temp_probe.celsius     = analog_to_celsius_probe(temp_probe.raw));
+  TERN_(HAS_TEMP_REDUNDANT, temp_redundant.celsius = analog_to_celsius_redundant(temp_redundant.raw));
 
   TERN_(FILAMENT_WIDTH_SENSOR, filwidth.update_measured_mm());
   TERN_(HAS_POWER_MONITOR,     power_monitor.capture_values());
 
   #if HAS_HOTEND
-
     static constexpr int8_t temp_dir[] = {
-      TERN(TEMP_SENSOR_0_IS_MAX_TC, 0, TEMPDIR(0))
+      #if TEMP_SENSOR_IS_ANY_MAX_TC(0)
+        0
+      #else
+        TEMPDIR(0)
+      #endif
       #if HAS_MULTI_HOTEND
-        , TERN(TEMP_SENSOR_1_IS_MAX_TC, 0, TEMPDIR(1))
+        #if TEMP_SENSOR_IS_ANY_MAX_TC(1)
+          , 0
+        #else
+          , TEMPDIR(1)
+        #endif
         #if HOTENDS > 2
           #define _TEMPDIR(N) , TEMPDIR(N)
           REPEAT_S(2, HOTENDS, _TEMPDIR)
   #endif
 
   // Init (and disable) SPI thermocouples
-  #if TEMP_SENSOR_0_IS_MAX6675 && PIN_EXISTS(MAX6675_CS)
+  #if TEMP_SENSOR_IS_MAX(0, MAX6675) && PIN_EXISTS(MAX6675_CS)
     OUT_WRITE(MAX6675_CS_PIN, HIGH);
   #endif
-  #if TEMP_SENSOR_1_IS_MAX6675 && PIN_EXISTS(MAX6675_CS2)
+  #if TEMP_SENSOR_IS_MAX(1, MAX6675) && PIN_EXISTS(MAX6675_CS2)
     OUT_WRITE(MAX6675_CS2_PIN, HIGH);
   #endif
-  #if TEMP_SENSOR_0_IS_MAX6675 && PIN_EXISTS(MAX31855_CS)
+  #if TEMP_SENSOR_IS_MAX(0, MAX6675) && PIN_EXISTS(MAX31855_CS)
     OUT_WRITE(MAX31855_CS_PIN, HIGH);
   #endif
-  #if TEMP_SENSOR_1_IS_MAX6675 && PIN_EXISTS(MAX31855_CS2)
+  #if TEMP_SENSOR_IS_MAX(1, MAX6675) && PIN_EXISTS(MAX31855_CS2)
     OUT_WRITE(MAX31855_CS2_PIN, HIGH);
   #endif
-  #if TEMP_SENSOR_0_IS_MAX6675 && PIN_EXISTS(MAX31865_CS)
+  #if TEMP_SENSOR_IS_MAX(0, MAX6675) && PIN_EXISTS(MAX31865_CS)
     OUT_WRITE(MAX31865_CS_PIN, HIGH);
   #endif
-  #if TEMP_SENSOR_1_IS_MAX6675 && PIN_EXISTS(MAX31865_CS2)
+  #if TEMP_SENSOR_IS_MAX(1, MAX6675) && PIN_EXISTS(MAX31865_CS2)
     OUT_WRITE(MAX31865_CS2_PIN, HIGH);
   #endif
 
   #if HAS_MAX31865_TEMP
-    TERN_(TEMP_SENSOR_0_IS_MAX31865, max31865_0.begin(MAX31865_2WIRE)); // MAX31865_2WIRE, MAX31865_3WIRE, MAX31865_4WIRE
-    TERN_(TEMP_SENSOR_1_IS_MAX31865, max31865_1.begin(MAX31865_2WIRE));
+    TERN_(TEMP_SENSOR_IS_MAX(0, MAX31865), max31865_0.begin(MAX31865_2WIRE)); // MAX31865_2WIRE, MAX31865_3WIRE, MAX31865_4WIRE
+    TERN_(TEMP_SENSOR_IS_MAX(1, MAX31865), max31865_1.begin(MAX31865_2WIRE));
   #endif
   #if HAS_MAX31855_TEMP
-    TERN_(TEMP_SENSOR_0_IS_MAX31855, max31855_0.begin());
-    TERN_(TEMP_SENSOR_1_IS_MAX31855, max31855_1.begin());
+    TERN_(TEMP_SENSOR_IS_MAX(0, MAX31855), max31855_0.begin());
+    TERN_(TEMP_SENSOR_IS_MAX(1, MAX31855), max31855_1.begin());
   #endif
   #if HAS_MAX6675_TEMP
-    TERN_(TEMP_SENSOR_0_IS_MAX6675, max6675_0.begin());
-    TERN_(TEMP_SENSOR_1_IS_MAX6675, max6675_1.begin());
+    TERN_(TEMP_SENSOR_IS_MAX(0, MAX6675), max6675_0.begin());
+    TERN_(TEMP_SENSOR_IS_MAX(1, MAX6675), max6675_1.begin());
   #endif
 
   #if MB(RUMBA)
     // Disable RUMBA JTAG in case the thermocouple extension is plugged on top of JTAG connector
     #define _AD(N) (TEMP_SENSOR_##N##_IS_AD595 || TEMP_SENSOR_##N##_IS_AD8495)
-    #if _AD(0) || _AD(1) || _AD(2) || _AD(BED) || _AD(CHAMBER)
+    #if _AD(0) || _AD(1) || _AD(2) || _AD(BED) || _AD(CHAMBER) || _AD(REDUNDANT)
       MCUCR = _BV(JTD);
       MCUCR = _BV(JTD);
     #endif
 
   // Thermistor activation by MCU pin
   #if PIN_EXISTS(TEMP_0_TR_ENABLE)
-    OUT_WRITE(TEMP_0_TR_ENABLE_PIN, ENABLED(TEMP_SENSOR_0_IS_MAX_TC));
+    OUT_WRITE(TEMP_0_TR_ENABLE_PIN,
+      #if TEMP_SENSOR_IS_ANY_MAX_TC(0)
+        1
+      #else
+        0
+      #endif
+    );
   #endif
   #if PIN_EXISTS(TEMP_1_TR_ENABLE)
-    OUT_WRITE(TEMP_1_TR_ENABLE_PIN, ENABLED(TEMP_SENSOR_1_IS_MAX_TC));
+    OUT_WRITE(TEMP_1_TR_ENABLE_PIN,
+      #if TEMP_SENSOR_IS_ANY_MAX_TC(1)
+        1
+      #else
+        0
+      #endif
+    );
   #endif
 
   #if HAS_HEATER_0
   #if HAS_TEMP_ADC_PROBE
     HAL_ANALOG_SELECT(TEMP_PROBE_PIN);
   #endif
+  #if HAS_TEMP_ADC_REDUNDANT
+    HAL_ANALOG_SELECT(TEMP_REDUNDANT_PIN);
+  #endif
   #if ENABLED(FILAMENT_WIDTH_SENSOR)
     HAL_ANALOG_SELECT(FILWIDTH_PIN);
   #endif
         temp_range[NR].raw_max -= TEMPDIR(NR) * (OVERSAMPLENR); \
     }while(0)
 
-    #define _MINMAX_TEST(N,M) (HOTENDS > N && TEMP_SENSOR_ ##N## _THERMISTOR_ID && TEMP_SENSOR_ ##N## _THERMISTOR_ID != 998 && TEMP_SENSOR_ ##N## _THERMISTOR_ID != 999 && defined(HEATER_##N##_##M##TEMP))
+    #define _MINMAX_TEST(N,M) (HOTENDS > N && TEMP_SENSOR_##N > 0 && TEMP_SENSOR_##N != 998 && TEMP_SENSOR_##N != 999 && defined(HEATER_##N##_##M##TEMP))
 
     #if _MINMAX_TEST(0, MIN)
       _TEMP_MIN_E(0);
     while (analog_to_celsius_cooler(mintemp_raw_COOLER) > COOLER_MINTEMP) mintemp_raw_COOLER += TEMPDIR(COOLER) * (OVERSAMPLENR);
     while (analog_to_celsius_cooler(maxtemp_raw_COOLER) < COOLER_MAXTEMP) maxtemp_raw_COOLER -= TEMPDIR(COOLER) * (OVERSAMPLENR);
   #endif
+
+  #if HAS_TEMP_REDUNDANT
+    temp_redundant.target = &(
+      #if TEMP_SENSOR_REDUNDANT_TARGET == -5 && HAS_TEMP_COOLER
+        temp_cooler
+      #elif TEMP_SENSOR_REDUNDANT_TARGET == -4 && HAS_TEMP_PROBE
+        temp_probe
+      #elif TEMP_SENSOR_REDUNDANT_TARGET == -2 && HAS_TEMP_CHAMBER
+        temp_chamber
+      #elif TEMP_SENSOR_REDUNDANT_TARGET == -1 && HAS_TEMP_BED
+        temp_bed
+      #else
+        temp_hotend[TEMP_SENSOR_REDUNDANT_TARGET]
+      #endif
+    );
+  #endif
 }
 
 #if HAS_THERMAL_PROTECTION
           , " ;  Idle Timeout:", heater_idle[idle_index].timed_out
         #endif
       );
-    //*/
+    */
 
     #if HEATER_IDLE_HANDLER
       // If the heater idle timeout expires, restart
     #else
       constexpr uint8_t hindex = 0;
       #define THERMO_TEMP(I) max_tc_temp
-      #if TEMP_SENSOR_1_IS_MAX31865
+      #if TEMP_SENSOR_IS_ANY_MAX_TC(1)
         #define THERMO_SEL(A,B) B
       #else
         #define THERMO_SEL(A,B) A
       #endif
-      #if TEMP_SENSOR_0_IS_MAX6675
+      #if TEMP_SENSOR_IS_MAX(0, MAX6675)
         #define MAX6675_WRITE(V)          WRITE(MAX6675_SS_PIN, V)
         #define MAX6675_SET_OUTPUT() SET_OUTPUT(MAX6675_SS_PIN)
       #else
     temp_hotend[0].update();
   #endif
 
-  #if HAS_TEMP_ADC_1
-    #if ENABLED(TEMP_SENSOR_1_AS_REDUNDANT)
-      temp_redundant.update();
-    #elif !TEMP_SENSOR_1_IS_MAX_TC
-      temp_hotend[1].update();
-    #endif
+  #if HAS_TEMP_ADC_1 && !TEMP_SENSOR_1_IS_MAX_TC
+    temp_hotend[1].update();
+  #endif
+
+  #if HAS_TEMP_ADC_REDUNDANT && !TEMP_SENSOR_REDUNDANT_IS_MAX_TC
+    temp_redundant.update();
   #endif
 
   TERN_(HAS_TEMP_ADC_2, temp_hotend[2].update());
 
   #if HAS_HOTEND
     HOTEND_LOOP() temp_hotend[e].reset();
-    TERN_(TEMP_SENSOR_1_AS_REDUNDANT, temp_redundant.reset());
   #endif
 
   TERN_(HAS_HEATED_BED, temp_bed.reset());
   TERN_(HAS_TEMP_CHAMBER, temp_chamber.reset());
   TERN_(HAS_TEMP_PROBE, temp_probe.reset());
   TERN_(HAS_TEMP_COOLER, temp_cooler.reset());
+  TERN_(HAS_TEMP_REDUNDANT, temp_redundant.reset());
 
   TERN_(HAS_JOY_ADC_X, joystick.x.reset());
   TERN_(HAS_JOY_ADC_Y, joystick.y.reset());
       case MeasureTemp_PROBE: ACCUMULATE_ADC(temp_probe); break;
     #endif
 
+    #if HAS_TEMP_ADC_REDUNDANT
+      case PrepareTemp_REDUNDANT: HAL_START_ADC(TEMP_REDUNDANT_PIN); break;
+      case MeasureTemp_REDUNDANT: ACCUMULATE_ADC(temp_redundant); break;
+    #endif
+
     #if HAS_TEMP_ADC_1
       case PrepareTemp_1: HAL_START_ADC(TEMP_1_PIN); break;
-      case MeasureTemp_1: ACCUMULATE_ADC(TERN(TEMP_SENSOR_1_AS_REDUNDANT, temp_redundant, temp_hotend[1])); break;
+      case MeasureTemp_1: ACCUMULATE_ADC(temp_hotend[1]); break;
     #endif
 
     #if HAS_TEMP_ADC_2
    *    Chamber: " C:nnn.nn /nnn.nn"
    *      Probe: " P:nnn.nn /nnn.nn"
    *     Cooler: " L:nnn.nn /nnn.nn"
+   *  Redundant: " R:nnn.nn /nnn.nn"
    *   Extruder: " T0:nnn.nn /nnn.nn"
    *   With ADC: " T0:nnn.nn /nnn.nn (nnn.nn)"
    */
       #if HAS_TEMP_COOLER
         case H_COOLER: k = 'L'; break;
       #endif
-      #if ENABLED(TEMP_SENSOR_1_AS_REDUNDANT)
+      #if HAS_TEMP_REDUNDANT
         case H_REDUNDANT: k = 'R'; break;
       #endif
     }
   }
 
   void Temperature::print_heater_states(const uint8_t target_extruder
-    OPTARG(TEMP_SENSOR_1_AS_REDUNDANT, const bool include_r/*=false*/)
+    OPTARG(HAS_TEMP_REDUNDANT, const bool include_r/*=false*/)
   ) {
     #if HAS_TEMP_HOTEND
       print_heater_state(H_NONE, degHotend(target_extruder), degTargetHotend(target_extruder) OPTARG(SHOW_TEMP_ADC_VALUES, rawHotendTemp(target_extruder)));
-      #if ENABLED(TEMP_SENSOR_1_AS_REDUNDANT)
-        if (include_r) print_heater_state(H_REDUNDANT, degHotendRedundant(), degTargetHotend(0) OPTARG(SHOW_TEMP_ADC_VALUES, rawHotendTempRedundant()));
-      #endif
     #endif
     #if HAS_HEATED_BED
       print_heater_state(H_BED, degBed(), degTargetBed() OPTARG(SHOW_TEMP_ADC_VALUES, rawBedTemp()));
     #if HAS_TEMP_PROBE
       print_heater_state(H_PROBE, degProbe(), 0 OPTARG(SHOW_TEMP_ADC_VALUES, rawProbeTemp()) );
     #endif
+    #if HAS_TEMP_REDUNDANT
+      if (include_r) print_heater_state(H_REDUNDANT, degRedundant(), degRedundantTarget() OPTARG(SHOW_TEMP_ADC_VALUES, rawRedundantTemp()));
+    #endif
     #if HAS_MULTI_HOTEND
       HOTEND_LOOP() print_heater_state((heater_id_t)e, degHotend(e), degTargetHotend(e) OPTARG(SHOW_TEMP_ADC_VALUES, rawHotendTemp(e)));
     #endif

Marlin/src/module/temperature.h

   #if HAS_TEMP_ADC_PROBE
     PrepareTemp_PROBE, MeasureTemp_PROBE,
   #endif
+  #if HAS_TEMP_ADC_REDUNDANT
+    PrepareTemp_REDUNDANT, MeasureTemp_REDUNDANT,
+  #endif
   #if HAS_TEMP_ADC_1
     PrepareTemp_1, MeasureTemp_1,
   #endif
   inline void update() { raw = acc; }
 } temp_info_t;
 
+#if HAS_TEMP_REDUNDANT
+  // A redundant temperature sensor
+  typedef struct RedundantTempInfo : public TempInfo {
+    temp_info_t* target;
+  } redundant_temp_info_t;
+#endif
+
 // A PWM heater with temperature sensor
 typedef struct HeaterInfo : public TempInfo {
   celsius_t target;
     #if TEMP_SENSOR_CHAMBER_IS_CUSTOM
       CTI_CHAMBER,
     #endif
-    #if COOLER_USER_THERMISTOR
+    #if TEMP_SENSOR_COOLER_IS_CUSTOM
       CTI_COOLER,
     #endif
+    #if TEMP_SENSOR_REDUNDANT_IS_CUSTOM
+      CTI_REDUNDANT,
+    #endif
     USER_THERMISTORS
   };
 
   public:
 
     #if HAS_HOTEND
-      #if ENABLED(TEMP_SENSOR_1_AS_REDUNDANT)
-        static temp_info_t temp_redundant;
-      #endif
       static hotend_info_t temp_hotend[HOTENDS];
       static const celsius_t hotend_maxtemp[HOTENDS];
       static inline celsius_t hotend_max_target(const uint8_t e) { return hotend_maxtemp[e] - (HOTEND_OVERSHOOT); }
     #if ENABLED(HAS_TEMP_COOLER)
       static cooler_info_t temp_cooler;
     #endif
+    #if HAS_TEMP_REDUNDANT
+      static redundant_temp_info_t temp_redundant;
+    #endif
 
     #if ENABLED(AUTO_POWER_E_FANS)
       static uint8_t autofan_speed[HOTENDS];
     #if HAS_TEMP_COOLER
       static celsius_float_t analog_to_celsius_cooler(const int16_t raw);
     #endif
+    #if HAS_TEMP_REDUNDANT
+      static celsius_float_t analog_to_celsius_redundant(const int16_t raw);
+    #endif
 
     #if HAS_FAN
 
       return TERN0(HAS_HOTEND, temp_hotend[HOTEND_INDEX].celsius);
     }
 
-    #if ENABLED(TEMP_SENSOR_1_AS_REDUNDANT)
-      static inline celsius_float_t degHotendRedundant() { return temp_redundant.celsius; }
-    #endif
-
     static inline celsius_t wholeDegHotend(const uint8_t E_NAME) {
       return TERN0(HAS_HOTEND, static_cast<celsius_t>(temp_hotend[HOTEND_INDEX].celsius + 0.5f));
     }
       static inline int16_t rawHotendTemp(const uint8_t E_NAME) {
         return TERN0(HAS_HOTEND, temp_hotend[HOTEND_INDEX].raw);
       }
-      #if ENABLED(TEMP_SENSOR_1_AS_REDUNDANT)
-        static inline int16_t rawHotendTempRedundant() { return temp_redundant.raw; }
-      #endif
     #endif
 
     static inline celsius_t degTargetHotend(const uint8_t E_NAME) {
       #endif
     #endif
 
+    #if HAS_TEMP_REDUNDANT
+      #if ENABLED(SHOW_TEMP_ADC_VALUES)
+        static inline int16_t rawRedundantTemp()         { return temp_redundant.raw; }
+        static inline int16_t rawRedundanTargetTemp()    { return (*temp_redundant.target).raw; }
+      #endif
+      static inline celsius_float_t degRedundant()       { return temp_redundant.celsius; }
+      static inline celsius_float_t degRedundantTarget() { return (*temp_redundant.target).celsius; }
+      static inline celsius_t wholeDegRedundant()        { return static_cast<celsius_t>(temp_redundant.celsius + 0.5f); }
+      static inline celsius_t wholeDegRedundantTarget()  { return static_cast<celsius_t>((*temp_redundant.target).celsius + 0.5f); }
+    #endif
+
     #if HAS_COOLER
       static inline void setTargetCooler(const celsius_t celsius) {
         temp_cooler.target = constrain(celsius, COOLER_MIN_TARGET, COOLER_MAX_TARGET);
 
     #if HAS_TEMP_SENSOR
       static void print_heater_states(const uint8_t target_extruder
-        OPTARG(TEMP_SENSOR_1_AS_REDUNDANT, const bool include_r=false)
+        OPTARG(HAS_TEMP_REDUNDANT, const bool include_r=false)
       );
       #if ENABLED(AUTO_REPORT_TEMPERATURES)
         struct AutoReportTemp { static void report(); };
 
     // MAX Thermocouples
     #if HAS_MAX_TC
-      #define MAX_TC_COUNT 1 + BOTH(TEMP_SENSOR_0_IS_MAX_TC, TEMP_SENSOR_1_IS_MAX_TC)
+      #define MAX_TC_COUNT COUNT_ENABLED(TEMP_SENSOR_0_IS_MAX_TC, TEMP_SENSOR_1_IS_MAX_TC, TEMP_SENSOR_REDUNDANT_IS_MAX_TC)
       #if MAX_TC_COUNT > 1
         #define HAS_MULTI_MAX_TC 1
         #define READ_MAX_TC(N) read_max_tc(N)

Marlin/src/module/thermistor/thermistor_1.h

 #pragma once
 
 // R25 = 100 kOhm, beta25 = 4092 K, 4.7 kOhm pull-up, bed thermistor
-const temp_entry_t temptable_1[] PROGMEM = {
+constexpr temp_entry_t temptable_1[] PROGMEM = {
   { OV(  23), 300 },
   { OV(  25), 295 },
   { OV(  27), 290 },

Marlin/src/module/thermistor/thermistor_10.h

 #pragma once
 
 // R25 = 100 kOhm, beta25 = 3960 K, 4.7 kOhm pull-up, RS thermistor 198-961
-const temp_entry_t temptable_10[] PROGMEM = {
+constexpr temp_entry_t temptable_10[] PROGMEM = {
   { OV(   1), 929 },
   { OV(  36), 299 },
   { OV(  71), 246 },

Marlin/src/module/thermistor/thermistor_1010.h

 #define REVERSE_TEMP_SENSOR_RANGE_1010 1
 
 // Pt1000 with 1k0 pullup
-const temp_entry_t temptable_1010[] PROGMEM = {
+constexpr temp_entry_t temptable_1010[] PROGMEM = {
   PtLine(  0, 1000, 1000),
   PtLine( 25, 1000, 1000),
   PtLine( 50, 1000, 1000),

Marlin/src/module/thermistor/thermistor_1047.h

 #define REVERSE_TEMP_SENSOR_RANGE_1047 1
 
 // Pt1000 with 4k7 pullup
-const temp_entry_t temptable_1047[] PROGMEM = {
+constexpr temp_entry_t temptable_1047[] PROGMEM = {
   // only a few values are needed as the curve is very flat
   PtLine(  0, 1000, 4700),
   PtLine( 50, 1000, 4700),

Marlin/src/module/thermistor/thermistor_11.h

 #pragma once
 
 // R25 = 100 kOhm, beta25 = 3950 K, 4.7 kOhm pull-up, QU-BD silicone bed QWG-104F-3950 thermistor
-const temp_entry_t temptable_11[] PROGMEM = {
+constexpr temp_entry_t temptable_11[] PROGMEM = {
   { OV(   1), 938 },
   { OV(  31), 314 },
   { OV(  41), 290 },

Marlin/src/module/thermistor/thermistor_110.h

 #define REVERSE_TEMP_SENSOR_RANGE_110 1
 
 // Pt100 with 1k0 pullup
-const temp_entry_t temptable_110[] PROGMEM = {
+constexpr temp_entry_t temptable_110[] PROGMEM = {
   // only a few values are needed as the curve is very flat
   PtLine(  0, 100, 1000),
   PtLine( 50, 100, 1000),

Marlin/src/module/thermistor/thermistor_12.h

 #pragma once
 
 // R25 = 100 kOhm, beta25 = 4700 K, 4.7 kOhm pull-up, (personal calibration for Makibox hot bed)
-const temp_entry_t temptable_12[] PROGMEM = {
+constexpr temp_entry_t temptable_12[] PROGMEM = {
   { OV(  35), 180 }, // top rating 180C
   { OV( 211), 140 },
   { OV( 233), 135 },

Marlin/src/module/thermistor/thermistor_13.h

 #pragma once
 
 // R25 = 100 kOhm, beta25 = 4100 K, 4.7 kOhm pull-up, Hisens thermistor
-const temp_entry_t temptable_13[] PROGMEM = {
+constexpr temp_entry_t temptable_13[] PROGMEM = {
   { OV( 20.04), 300 },
   { OV( 23.19), 290 },
   { OV( 26.71), 280 },

Marlin/src/module/thermistor/thermistor_147.h

 #define REVERSE_TEMP_SENSOR_RANGE_147 1
 
 // Pt100 with 4k7 pullup
-const temp_entry_t temptable_147[] PROGMEM = {
+constexpr temp_entry_t temptable_147[] PROGMEM = {
   // only a few values are needed as the curve is very flat
   PtLine(  0, 100, 4700),
   PtLine( 50, 100, 4700),

Marlin/src/module/thermistor/thermistor_15.h

 #pragma once
 
  // 100k bed thermistor in JGAurora A5. Calibrated by Sam Pinches 21st Jan 2018 using cheap k-type thermocouple inserted into heater block, using TM-902C meter.
-const temp_entry_t temptable_15[] PROGMEM = {
+constexpr temp_entry_t temptable_15[] PROGMEM = {
   { OV(  31), 275 },
   { OV(  33), 270 },
   { OV(  35), 260 },

Marlin/src/module/thermistor/thermistor_17.h

 #pragma once
 
 // Dagoma NTC 100k white thermistor
-const temp_entry_t temptable_17[] PROGMEM = {
+constexpr temp_entry_t temptable_17[] PROGMEM = {
   { OV(  16),  309 },
   { OV(  18),  307 },
   { OV(  20),  300 },

Marlin/src/module/thermistor/thermistor_18.h

 #pragma once
 
 // ATC Semitec 204GT-2 (4.7k pullup) Dagoma.Fr - MKS_Base_DKU001327 - version (measured/tested/approved)
-const temp_entry_t temptable_18[] PROGMEM = {
+constexpr temp_entry_t temptable_18[] PROGMEM = {
   { OV(   1), 713 },
   { OV(  17), 284 },
   { OV(  20), 275 },

Marlin/src/module/thermistor/thermistor_2.h

 // Verified by linagee. Source: https://www.mouser.com/datasheet/2/362/semitec%20usa%20corporation_gtthermistor-1202937.pdf
 // Calculated using 4.7kohm pullup, voltage divider math, and manufacturer provided temp/resistance
 //
-const temp_entry_t temptable_2[] PROGMEM = {
+constexpr temp_entry_t temptable_2[] PROGMEM = {
   { OV(   1), 848 },
   { OV(  30), 300 }, // top rating 300C
   { OV(  34), 290 },

Marlin/src/module/thermistor/thermistor_20.h

 #define REVERSE_TEMP_SENSOR_RANGE_20 1
 
 // Pt100 with INA826 amp on Ultimaker v2.0 electronics
-const temp_entry_t temptable_20[] PROGMEM = {
+constexpr temp_entry_t temptable_20[] PROGMEM = {
   { OV(  0),    0 },
   { OV(227),    1 },
   { OV(236),   10 },

Marlin/src/module/thermistor/thermistor_201.h

 #define REVERSE_TEMP_SENSOR_RANGE_201 1
 
 // Pt100 with LMV324 amp on Overlord v1.1 electronics
-const temp_entry_t temptable_201[] PROGMEM = {
+constexpr temp_entry_t temptable_201[] PROGMEM = {
   { OV(   0),   0 },
   { OV(   8),   1 },
   { OV(  23),   6 },

Marlin/src/module/thermistor/thermistor_202.h

 // Temptable sent from dealer technologyoutlet.co.uk
 //
 
-const temp_entry_t temptable_202[] PROGMEM = {
+constexpr temp_entry_t temptable_202[] PROGMEM = {
   { OV(   1), 864 },
   { OV(  35), 300 },
   { OV(  38), 295 },

Marlin/src/module/thermistor/thermistor_21.h

 
 // Pt100 with INA826 amplifier board with 5v supply based on Thermistor 20, with 3v3 ADC reference on the mainboard.
 // If the ADC reference and INA826 board supply voltage are identical, Thermistor 20 instead.
-const temp_entry_t temptable_21[] PROGMEM = {
+constexpr temp_entry_t temptable_21[] PROGMEM = {
   { OV(  0),    0 },
   { OV(227),    1 },
   { OV(236),   10 },

Marlin/src/module/thermistor/thermistor_22.h

  */
 
 // 100k hotend thermistor with 4.7k pull up to 3.3v and 220R to analog input as in GTM32 Pro vB
-const temp_entry_t temptable_22[] PROGMEM = {
+constexpr temp_entry_t temptable_22[] PROGMEM = {
   { OV(   1), 352 },
   { OV(   6), 341 },
   { OV(  11), 330 },

Marlin/src/module/thermistor/thermistor_23.h

  */
 
 // 100k hotbed thermistor with 4.7k pull up to 3.3v and 220R to analog input as in GTM32 Pro vB
-const temp_entry_t temptable_23[] PROGMEM = {
+constexpr temp_entry_t temptable_23[] PROGMEM = {
   { OV(   1), 938 },
   { OV(  11), 423 },
   { OV(  21), 351 },

Marlin/src/module/thermistor/thermistor_3.h

 #pragma once
 
 // R25 = 100 kOhm, beta25 = 4120 K, 4.7 kOhm pull-up, mendel-parts
-const temp_entry_t temptable_3[] PROGMEM = {
+constexpr temp_entry_t temptable_3[] PROGMEM = {
   { OV(   1), 864 },
   { OV(  21), 300 },
   { OV(  25), 290 },

Marlin/src/module/thermistor/thermistor_30.h

 // B Value Tolerance         + / - 1%
 // Kis3d Silicone Heater 24V 200W/300W with 6mm Precision cast plate (EN AW 5083)
 // Temperature setting time 10 min to determine the 12Bit ADC value on the surface. (le3tspeak)
-const temp_entry_t temptable_30[] PROGMEM = {
+constexpr temp_entry_t temptable_30[] PROGMEM = {
   { OV(   1), 938 },
   { OV( 298), 125 }, // 1193 - 125°
   { OV( 321), 121 }, // 1285 - 121°

Marlin/src/module/thermistor/thermistor_331.h

 #define OVM(V) OV((V)*(0.327/0.5))
 
 // R25 = 100 kOhm, beta25 = 4092 K, 4.7 kOhm pull-up, bed thermistor
-const temp_entry_t temptable_331[] PROGMEM = {
+constexpr temp_entry_t temptable_331[] PROGMEM = {
   { OVM(  23), 300 },
   { OVM(  25), 295 },
   { OVM(  27), 290 },

Marlin/src/module/thermistor/thermistor_332.h

 #define OVM(V) OV((V)*(0.327/0.327))
 
 // R25 = 100 kOhm, beta25 = 4092 K, 4.7 kOhm pull-up, bed thermistor
-const temp_entry_t temptable_332[] PROGMEM = {
+constexpr temp_entry_t temptable_332[] PROGMEM = {
   { OVM( 268), 150 },
   { OVM( 293), 145 },
   { OVM( 320), 141 },

Marlin/src/module/thermistor/thermistor_4.h

 #pragma once
 
 // R25 = 10 kOhm, beta25 = 3950 K, 4.7 kOhm pull-up, Generic 10k thermistor
-const temp_entry_t temptable_4[] PROGMEM = {
+constexpr temp_entry_t temptable_4[] PROGMEM = {
   { OV(   1), 430 },
   { OV(  54), 137 },
   { OV( 107), 107 },

Marlin/src/module/thermistor/thermistor_5.h

 // ATC Semitec 104GT-2/104NT-4-R025H42G (Used in ParCan)
 // Verified by linagee. Source: https://www.mouser.com/datasheet/2/362/semitec%20usa%20corporation_gtthermistor-1202937.pdf
 // Calculated using 4.7kohm pullup, voltage divider math, and manufacturer provided temp/resistance
-const temp_entry_t temptable_5[] PROGMEM = {
+constexpr temp_entry_t temptable_5[] PROGMEM = {
   { OV(   1), 713 },
   { OV(  17), 300 }, // top rating 300C
   { OV(  20), 290 },

Marlin/src/module/thermistor/thermistor_501.h

 #pragma once
 
 // 100k Zonestar thermistor. Adjusted By Hally
-const temp_entry_t temptable_501[] PROGMEM = {
+constexpr temp_entry_t temptable_501[] PROGMEM = {
    { OV(   1), 713 },
    { OV(  14), 300 }, // Top rating 300C
    { OV(  16), 290 },

Marlin/src/module/thermistor/thermistor_502.h

 
 // Unknown thermistor for the Zonestar P802M hot bed. Adjusted By Nerseth
 // These were the shipped settings from Zonestar in original firmware: P802M_8_Repetier_V1.6_Zonestar.zip
-const temp_entry_t temptable_502[] PROGMEM = {
+constexpr temp_entry_t temptable_502[] PROGMEM = {
    { OV(  56.0 / 4), 300 },
    { OV( 187.0 / 4), 250 },
    { OV( 615.0 / 4), 190 },

Marlin/src/module/thermistor/thermistor_503.h

 
 // Zonestar (Z8XM2) Heated Bed thermistor. Added By AvanOsch
 // These are taken from the Zonestar settings in original Repetier firmware: Z8XM2_ZRIB_LCD12864_V51.zip
-const temp_entry_t temptable_503[] PROGMEM = {
+constexpr temp_entry_t temptable_503[] PROGMEM = {
    { OV(  12), 300 },
    { OV(  27), 270 },
    { OV(  47), 250 },

Marlin/src/module/thermistor/thermistor_51.h

 // Verified by linagee.
 // Calculated using 1kohm pullup, voltage divider math, and manufacturer provided temp/resistance
 // Advantage: Twice the resolution and better linearity from 150C to 200C
-const temp_entry_t temptable_51[] PROGMEM = {
+constexpr temp_entry_t temptable_51[] PROGMEM = {
   { OV(   1), 350 },
   { OV( 190), 250 }, // top rating 250C
   { OV( 203), 245 },

Marlin/src/module/thermistor/thermistor_512.h

 
 // 100k thermistor supplied with RPW-Ultra hotend, 4.7k pullup
 
-const temp_entry_t temptable_512[] PROGMEM = {
+constexpr temp_entry_t temptable_512[] PROGMEM = {
   { OV(26),  300 },
   { OV(28),  295 },
   { OV(30),  290 },

Marlin/src/module/thermistor/thermistor_52.h

 // Verified by linagee. Source: https://www.mouser.com/datasheet/2/362/semitec%20usa%20corporation_gtthermistor-1202937.pdf
 // Calculated using 1kohm pullup, voltage divider math, and manufacturer provided temp/resistance
 // Advantage: More resolution and better linearity from 150C to 200C
-const temp_entry_t temptable_52[] PROGMEM = {
+constexpr temp_entry_t temptable_52[] PROGMEM = {
   { OV(   1), 500 },
   { OV( 125), 300 }, // top rating 300C
   { OV( 142), 290 },

Marlin/src/module/thermistor/thermistor_55.h

 // Verified by linagee. Source: https://www.mouser.com/datasheet/2/362/semitec%20usa%20corporation_gtthermistor-1202937.pdf
 // Calculated using 1kohm pullup, voltage divider math, and manufacturer provided temp/resistance
 // Advantage: More resolution and better linearity from 150C to 200C
-const temp_entry_t temptable_55[] PROGMEM = {
+constexpr temp_entry_t temptable_55[] PROGMEM = {
   { OV(   1), 500 },
   { OV(  76), 300 },
   { OV(  87), 290 },

Marlin/src/module/thermistor/thermistor_6.h

 #pragma once
 
 // R25 = 100 kOhm, beta25 = 4092 K, 8.2 kOhm pull-up, 100k Epcos (?) thermistor
-const temp_entry_t temptable_6[] PROGMEM = {
+constexpr temp_entry_t temptable_6[] PROGMEM = {
   { OV(   1), 350 },
   { OV(  28), 250 }, // top rating 250C
   { OV(  31), 245 },

Marlin/src/module/thermistor/thermistor_60.h

 // beta: 3950
 // min adc: 1 at 0.0048828125 V
 // max adc: 1023 at 4.9951171875 V
-const temp_entry_t temptable_60[] PROGMEM = {
+constexpr temp_entry_t temptable_60[] PROGMEM = {
   { OV(  51), 272 },
   { OV(  61), 258 },
   { OV(  71), 247 },

Marlin/src/module/thermistor/thermistor_61.h

 // Resistance Tolerance     + / -1%
 // B Value             3950K at 25/50 deg. C
 // B Value Tolerance         + / - 1%
-const temp_entry_t temptable_61[] PROGMEM = {
+constexpr temp_entry_t temptable_61[] PROGMEM = {
   { OV(   2.00), 420 }, // Guestimate to ensure we dont lose a reading and drop temps to -50 when over
   { OV(  12.07), 350 },
   { OV(  12.79), 345 },

Marlin/src/module/thermistor/thermistor_66.h

 #pragma once
 
 // R25 = 2.5 MOhm, beta25 = 4500 K, 4.7 kOhm pull-up, DyzeDesign 500 °C Thermistor
-const temp_entry_t temptable_66[] PROGMEM = {
+constexpr temp_entry_t temptable_66[] PROGMEM = {
   { OV(  17.5), 850 },
   { OV(  17.9), 500 },
   { OV(  21.7), 480 },

Marlin/src/module/thermistor/thermistor_666.h

  * B: 0.00031362
  * C: -2.03978e-07
  */
-const temp_entry_t temptable_666[] PROGMEM = {
+constexpr temp_entry_t temptable_666[] PROGMEM = {
   { OV(  1), 794 },
   { OV( 18), 288 },
   { OV( 35), 234 },

Marlin/src/module/thermistor/thermistor_67.h

 #pragma once
 
 // R25 = 500 KOhm, beta25 = 3800 K, 4.7 kOhm pull-up, SliceEngineering 450 °C Thermistor
-const temp_entry_t temptable_67[] PROGMEM = {
+constexpr temp_entry_t temptable_67[] PROGMEM = {
   { OV(  22 ),  500 },
   { OV(  23 ),  490 },
   { OV(  25 ),  480 },

Marlin/src/module/thermistor/thermistor_7.h

 #pragma once
 
 // R25 = 100 kOhm, beta25 = 3974 K, 4.7 kOhm pull-up, Honeywell 135-104LAG-J01
-const temp_entry_t temptable_7[] PROGMEM = {
+constexpr temp_entry_t temptable_7[] PROGMEM = {
   { OV(   1), 941 },
   { OV(  19), 362 },
   { OV(  37), 299 }, // top rating 300C

Marlin/src/module/thermistor/thermistor_70.h

 // ANENG AN8009 DMM with a K-type probe used for measurements.
 
 // R25 = 100 kOhm, beta25 = 4100 K, 4.7 kOhm pull-up, bqh2 stock thermistor
-const temp_entry_t temptable_70[] PROGMEM = {
+constexpr temp_entry_t temptable_70[] PROGMEM = {
   { OV(  18), 270 },
   { OV(  27), 248 },
   { OV(  34), 234 },

Marlin/src/module/thermistor/thermistor_71.h

 // Beta = 3974
 // R1 = 0 Ohm
 // R2 = 4700 Ohm
-const temp_entry_t temptable_71[] PROGMEM = {
+constexpr temp_entry_t temptable_71[] PROGMEM = {
   { OV(  35), 300 },
   { OV(  51), 269 },
   { OV(  59), 258 },

Marlin/src/module/thermistor/thermistor_75.h

 
 //#define HIGH_TEMP_RANGE_75
 
-const temp_entry_t temptable_75[] PROGMEM = { // Generic Silicon Heat Pad with NTC 100K MGB18-104F39050L32 thermistor
+constexpr temp_entry_t temptable_75[] PROGMEM = { // Generic Silicon Heat Pad with NTC 100K MGB18-104F39050L32 thermistor
   { OV(111.06), 200 }, // v=0.542 r=571.747 res=0.501 degC/count
 
   #ifdef HIGH_TEMP_RANGE_75

Marlin/src/module/thermistor/thermistor_8.h

 #pragma once
 
 // R25 = 100 kOhm, beta25 = 3950 K, 10 kOhm pull-up, NTCS0603E3104FHT
-const temp_entry_t temptable_8[] PROGMEM = {
+constexpr temp_entry_t temptable_8[] PROGMEM = {
   { OV(   1), 704 },
   { OV(  54), 216 },
   { OV( 107), 175 },

Marlin/src/module/thermistor/thermistor_9.h

 #pragma once
 
 // R25 = 100 kOhm, beta25 = 3960 K, 4.7 kOhm pull-up, GE Sensing AL03006-58.2K-97-G1
-const temp_entry_t temptable_9[] PROGMEM = {
+constexpr temp_entry_t temptable_9[] PROGMEM = {
   { OV(   1), 936 },
   { OV(  36), 300 },
   { OV(  71), 246 },

Marlin/src/module/thermistor/thermistor_99.h

 
 // 100k bed thermistor with a 10K pull-up resistor - made by $ buildroot/share/scripts/createTemperatureLookupMarlin.py --rp=10000
 
-const temp_entry_t temptable_99[] PROGMEM = {
+constexpr temp_entry_t temptable_99[] PROGMEM = {
   { OV(  5.81), 350 }, // v=0.028   r=    57.081  res=13.433 degC/count
   { OV(  6.54), 340 }, // v=0.032   r=    64.248  res=11.711 degC/count
   { OV(  7.38), 330 }, // v=0.036   r=    72.588  res=10.161 degC/count

Marlin/src/module/thermistor/thermistor_998.h

   #define DUMMY_THERMISTOR_998_VALUE 25
 #endif
 
-const temp_entry_t temptable_998[] PROGMEM = {
+constexpr temp_entry_t temptable_998[] PROGMEM = {
   { OV(   1), DUMMY_THERMISTOR_998_VALUE },
   { OV(1023), DUMMY_THERMISTOR_998_VALUE }
 };

Marlin/src/module/thermistor/thermistor_999.h

   #define DUMMY_THERMISTOR_999_VALUE 25
 #endif
 
-const temp_entry_t temptable_999[] PROGMEM = {
+constexpr temp_entry_t temptable_999[] PROGMEM = {
   { OV(   1), DUMMY_THERMISTOR_999_VALUE },
   { OV(1023), DUMMY_THERMISTOR_999_VALUE }
 };

Marlin/src/module/thermistor/thermistors.h

 #define OV_SCALE(N) (N)
 #define OV(N) int16_t(OV_SCALE(N) * (OVERSAMPLENR) * (THERMISTOR_TABLE_SCALE))
 
-#define ANY_THERMISTOR_IS(n) (TEMP_SENSOR_0_THERMISTOR_ID == n || TEMP_SENSOR_1_THERMISTOR_ID == n || TEMP_SENSOR_2_THERMISTOR_ID == n || TEMP_SENSOR_3_THERMISTOR_ID == n || TEMP_SENSOR_4_THERMISTOR_ID == n || TEMP_SENSOR_5_THERMISTOR_ID == n || TEMP_SENSOR_6_THERMISTOR_ID == n || TEMP_SENSOR_7_THERMISTOR_ID == n || TEMP_SENSOR_BED_THERMISTOR_ID == n || TEMP_SENSOR_CHAMBER_THERMISTOR_ID == n || TEMP_SENSOR_COOLER_THERMISTOR_ID == n || TEMP_SENSOR_PROBE_THERMISTOR_ID == n)
+#define TEMP_SENSOR_IS(n,H) (n == TEMP_SENSOR_##H)
+#define ANY_THERMISTOR_IS(n) ( TEMP_SENSOR_IS(n, 0) || TEMP_SENSOR_IS(n, 1) \
+                            || TEMP_SENSOR_IS(n, 2) || TEMP_SENSOR_IS(n, 3) \
+                            || TEMP_SENSOR_IS(n, 4) || TEMP_SENSOR_IS(n, 5) \
+                            || TEMP_SENSOR_IS(n, 6) || TEMP_SENSOR_IS(n, 7) \
+                            || TEMP_SENSOR_IS(n, BED) \
+                            || TEMP_SENSOR_IS(n, CHAMBER) \
+                            || TEMP_SENSOR_IS(n, COOLER) \
+                            || TEMP_SENSOR_IS(n, PROBE) \
+                            || TEMP_SENSOR_IS(n, REDUNDANT) )
 
 typedef struct { int16_t value; celsius_t celsius; } temp_entry_t;
 
   #include "thermistor_999.h"
 #endif
 #if ANY_THERMISTOR_IS(1000) // Custom
-  const temp_entry_t temptable_1000[] PROGMEM = { { 0, 0 } };
+  constexpr temp_entry_t temptable_1000[] PROGMEM = { { 0, 0 } };
 #endif
 
 #define _TT_NAME(_N) temptable_ ## _N
 #define TT_NAME(_N) _TT_NAME(_N)
 
-
-#if TEMP_SENSOR_0_THERMISTOR_ID
-  #define TEMPTABLE_0 TT_NAME(TEMP_SENSOR_0_THERMISTOR_ID)
+#if TEMP_SENSOR_0 > 0
+  #define TEMPTABLE_0 TT_NAME(TEMP_SENSOR_0)
   #define TEMPTABLE_0_LEN COUNT(TEMPTABLE_0)
-#elif TEMP_SENSOR_0_IS_THERMISTOR
-  #error "No heater 0 thermistor table specified"
 #else
   #define TEMPTABLE_0 nullptr
   #define TEMPTABLE_0_LEN 0
 #endif
 
-#if TEMP_SENSOR_1_THERMISTOR_ID
-  #define TEMPTABLE_1 TT_NAME(TEMP_SENSOR_1_THERMISTOR_ID)
+#if TEMP_SENSOR_1 > 0
+  #define TEMPTABLE_1 TT_NAME(TEMP_SENSOR_1)
   #define TEMPTABLE_1_LEN COUNT(TEMPTABLE_1)
-#elif TEMP_SENSOR_1_IS_THERMISTOR
-  #error "No heater 1 thermistor table specified"
 #else
   #define TEMPTABLE_1 nullptr
   #define TEMPTABLE_1_LEN 0
 #endif
 
-#if TEMP_SENSOR_2_THERMISTOR_ID
-  #define TEMPTABLE_2 TT_NAME(TEMP_SENSOR_2_THERMISTOR_ID)
+#if TEMP_SENSOR_2 > 0
+  #define TEMPTABLE_2 TT_NAME(TEMP_SENSOR_2)
   #define TEMPTABLE_2_LEN COUNT(TEMPTABLE_2)
-#elif TEMP_SENSOR_2_IS_THERMISTOR
-  #error "No heater 2 thermistor table specified"
 #else
   #define TEMPTABLE_2 nullptr
   #define TEMPTABLE_2_LEN 0
 #endif
 
-#if TEMP_SENSOR_3_THERMISTOR_ID
-  #define TEMPTABLE_3 TT_NAME(TEMP_SENSOR_3_THERMISTOR_ID)
+#if TEMP_SENSOR_3 > 0
+  #define TEMPTABLE_3 TT_NAME(TEMP_SENSOR_3)
   #define TEMPTABLE_3_LEN COUNT(TEMPTABLE_3)
-#elif TEMP_SENSOR_3_IS_THERMISTOR
-  #error "No heater 3 thermistor table specified"
 #else
   #define TEMPTABLE_3 nullptr
   #define TEMPTABLE_3_LEN 0
 #endif
 
-#if TEMP_SENSOR_4_THERMISTOR_ID
-  #define TEMPTABLE_4 TT_NAME(TEMP_SENSOR_4_THERMISTOR_ID)
+#if TEMP_SENSOR_4 > 0
+  #define TEMPTABLE_4 TT_NAME(TEMP_SENSOR_4)
   #define TEMPTABLE_4_LEN COUNT(TEMPTABLE_4)
-#elif TEMP_SENSOR_4_IS_THERMISTOR
-  #error "No heater 4 thermistor table specified"
 #else
   #define TEMPTABLE_4 nullptr
   #define TEMPTABLE_4_LEN 0
 #endif
 
-#if TEMP_SENSOR_5_THERMISTOR_ID
-  #define TEMPTABLE_5 TT_NAME(TEMP_SENSOR_5_THERMISTOR_ID)
+#if TEMP_SENSOR_5 > 0
+  #define TEMPTABLE_5 TT_NAME(TEMP_SENSOR_5)
   #define TEMPTABLE_5_LEN COUNT(TEMPTABLE_5)
-#elif TEMP_SENSOR_5_IS_THERMISTOR
-  #error "No heater 5 thermistor table specified"
 #else
   #define TEMPTABLE_5 nullptr
   #define TEMPTABLE_5_LEN 0
 #endif
 
-#if TEMP_SENSOR_6_THERMISTOR_ID
-  #define TEMPTABLE_6 TT_NAME(TEMP_SENSOR_6_THERMISTOR_ID)
+#if TEMP_SENSOR_6 > 0
+  #define TEMPTABLE_6 TT_NAME(TEMP_SENSOR_6)
   #define TEMPTABLE_6_LEN COUNT(TEMPTABLE_6)
-#elif TEMP_SENSOR_6_IS_THERMISTOR
-  #error "No heater 6 thermistor table specified"
 #else
   #define TEMPTABLE_6 nullptr
   #define TEMPTABLE_6_LEN 0
 #endif
 
-#if TEMP_SENSOR_7_THERMISTOR_ID
-  #define TEMPTABLE_7 TT_NAME(TEMP_SENSOR_7_THERMISTOR_ID)
+#if TEMP_SENSOR_7 > 0
+  #define TEMPTABLE_7 TT_NAME(TEMP_SENSOR_7)
   #define TEMPTABLE_7_LEN COUNT(TEMPTABLE_7)
-#elif TEMP_SENSOR_7_IS_THERMISTOR
-  #error "No heater 7 thermistor table specified"
 #else
   #define TEMPTABLE_7 nullptr
   #define TEMPTABLE_7_LEN 0
 #endif
 
-#ifdef TEMP_SENSOR_BED_THERMISTOR_ID
-  #define TEMPTABLE_BED TT_NAME(TEMP_SENSOR_BED_THERMISTOR_ID)
+#if TEMP_SENSOR_BED > 0
+  #define TEMPTABLE_BED TT_NAME(TEMP_SENSOR_BED)
   #define TEMPTABLE_BED_LEN COUNT(TEMPTABLE_BED)
-#elif TEMP_SENSOR_BED_IS_THERMISTOR
-  #error "No bed thermistor table specified"
 #else
   #define TEMPTABLE_BED_LEN 0
 #endif
 
-#ifdef TEMP_SENSOR_CHAMBER_THERMISTOR_ID
-  #define TEMPTABLE_CHAMBER TT_NAME(TEMP_SENSOR_CHAMBER_THERMISTOR_ID)
+#if TEMP_SENSOR_CHAMBER > 0
+  #define TEMPTABLE_CHAMBER TT_NAME(TEMP_SENSOR_CHAMBER)
   #define TEMPTABLE_CHAMBER_LEN COUNT(TEMPTABLE_CHAMBER)
-#elif TEMP_SENSOR_CHAMBER_IS_THERMISTOR
-  #error "No chamber thermistor table specified"
 #else
   #define TEMPTABLE_CHAMBER_LEN 0
 #endif
 
-#ifdef TEMP_SENSOR_COOLER_THERMISTOR_ID
-  #define TEMPTABLE_COOLER TT_NAME(TEMP_SENSOR_COOLER_THERMISTOR_ID)
+#if TEMP_SENSOR_COOLER > 0
+  #define TEMPTABLE_COOLER TT_NAME(TEMP_SENSOR_COOLER)
   #define TEMPTABLE_COOLER_LEN COUNT(TEMPTABLE_COOLER)
-#elif TEMP_SENSOR_COOLER_IS_THERMISTOR
-  #error "No cooler thermistor table specified"
 #else
   #define TEMPTABLE_COOLER_LEN 0
 #endif
-#ifdef TEMP_SENSOR_PROBE_THERMISTOR_ID
-  #define TEMPTABLE_PROBE TT_NAME(TEMP_SENSOR_PROBE_THERMISTOR_ID)
+
+#if TEMP_SENSOR_PROBE > 0
+  #define TEMPTABLE_PROBE TT_NAME(TEMP_SENSOR_PROBE)
   #define TEMPTABLE_PROBE_LEN COUNT(TEMPTABLE_PROBE)
-#elif TEMP_SENSOR_PROBE_IS_THERMISTOR
-  #error "No probe thermistor table specified"
 #else
   #define TEMPTABLE_PROBE_LEN 0
 #endif
 
+#if TEMP_SENSOR_REDUNDANT > 0
+  #define TEMPTABLE_REDUNDANT TT_NAME(TEMP_SENSOR_REDUNDANT)
+  #define TEMPTABLE_REDUNDANT_LEN COUNT(TEMPTABLE_REDUNDANT)
+#else
+  #define TEMPTABLE_REDUNDANT_LEN 0
+#endif
+
 // The SCAN_THERMISTOR_TABLE macro needs alteration?
-static_assert(
-     TEMPTABLE_0_LEN < 256 && TEMPTABLE_1_LEN < 256
-  && TEMPTABLE_2_LEN < 256 && TEMPTABLE_3_LEN < 256
-  && TEMPTABLE_4_LEN < 256 && TEMPTABLE_5_LEN < 256
-  && TEMPTABLE_6_LEN < 256 && TEMPTABLE_7_LEN < 256
-  && TEMPTABLE_BED_LEN < 256 && TEMPTABLE_CHAMBER_LEN < 256
-  && TEMPTABLE_COOLER_LEN < 256 && TEMPTABLE_PROBE_LEN < 256,
-  "Temperature conversion tables over 255 entries need special consideration."
+static_assert(255 > TEMPTABLE_0_LEN || 255 > TEMPTABLE_1_LEN || 255 > TEMPTABLE_2_LEN || 255 > TEMPTABLE_3_LEN
+           || 255 > TEMPTABLE_4_LEN || 255 > TEMPTABLE_5_LEN || 255 > TEMPTABLE_6_LEN || 255 > TEMPTABLE_7_LEN
+           || 255 > TEMPTABLE_BED_LEN
+           || 255 > TEMPTABLE_CHAMBER_LEN
+           || 255 > TEMPTABLE_COOLER_LEN
+           || 255 > TEMPTABLE_PROBE_LEN
+           || 255 > TEMPTABLE_REDUNDANT_LEN
+  , "Temperature conversion tables over 255 entries need special consideration."
 );
 
 // Set the high and low raw values for the heaters
 // For thermistors the highest temperature results in the lowest ADC value
 // For thermocouples the highest temperature results in the highest ADC value
 
-#define __TT_REV(N)   REVERSE_TEMP_SENSOR_RANGE_##N
-#define _TT_REV(N)    __TT_REV(N)
-#define TT_REV(N)     _TT_REV(TEMP_SENSOR_##N##_THERMISTOR_ID)
+#define _TT_REV(N)    REVERSE_TEMP_SENSOR_RANGE_##N
+#define TT_REV(N)     TERN0(TEMP_SENSOR_##N##_IS_THERMISTOR, DEFER4(_TT_REV)(TEMP_SENSOR_##N))
 #define _TT_REVRAW(N) !TEMP_SENSOR_##N##_IS_THERMISTOR
 #define TT_REVRAW(N)  (TT_REV(N) || _TT_REVRAW(N))
 
     #define TEMP_SENSOR_PROBE_RAW_LO_TEMP MAX_RAW_THERMISTOR_VALUE
   #endif
 #endif
+#ifndef TEMP_SENSOR_REDUNDANT_RAW_HI_TEMP
+  #if TT_REVRAW(REDUNDANT)
+    #define TEMP_SENSOR_REDUNDANT_RAW_HI_TEMP MAX_RAW_THERMISTOR_VALUE
+    #define TEMP_SENSOR_REDUNDANT_RAW_LO_TEMP 0
+  #else
+    #define TEMP_SENSOR_REDUNDANT_RAW_HI_TEMP 0
+    #define TEMP_SENSOR_REDUNDANT_RAW_LO_TEMP MAX_RAW_THERMISTOR_VALUE
+  #endif
+#endif
 
 #undef __TT_REV
 #undef _TT_REV

buildroot/bin/mftest

 TESTPATH=buildroot/tests
 
 STATE_FILE="./.pio/.mftestrc"
-SED=$(which gsed || which sed)
+SED=$(which gsed sed | head -n1)
 
 shopt -s extglob nocasematch
 

buildroot/bin/opt_disable

 # exit on first failure
 set -e
 
-SED=$(which gsed || which sed)
+SED=$(which gsed sed | head -n1)
 
 for opt in "$@" ; do
   DID=0 ; FOUND=0

buildroot/bin/opt_enable

 # exit on first failure
 set -e
 
-SED=$(which gsed || which sed)
+SED=$(which gsed sed | head -n1)
 
 for opt in "$@" ; do
   DID=0 ; FOUND=0

buildroot/bin/opt_set

 # exit on first failure
 set -e
 
-SED=$(which gsed || which sed)
+SED=$(which gsed sed | head -n1)
 
 while [[ $# > 1 ]]; do
   DID=0

buildroot/bin/pins_set

 PIN=$2
 VAL=$3
 
-SED=$(which gsed || which sed)
+SED=$(which gsed sed | head -n1)
 eval "${SED} -i '/^[[:blank:]]*\(\/\/\)*[[:blank:]]*\(#define \+${PIN}\b\).*$/{s//\2 ${VAL}/;h};\${x;/./{x;q0};x;q9}' Marlin/src/pins/$DIR/pins_${NAM}.h" ||
 (echo "ERROR: pins_set Can't find ${PIN}" >&2 && exit 9)

buildroot/share/git/mfconfig

   ((COMMIT_STEPS)) && git add . >/dev/null && git commit -m "Reset TPARA..." >/dev/null
 
   # Update the %VERSION% in the README.md file
-  SED=$(which gsed || which sed)
+  SED=$(which gsed sed | head -n1)
   VERS=$( echo $EXPORT | $SED 's/release-//' )
   eval "${SED} -E -i~ -e 's/%VERSION%/$VERS/g' README.md"
   rm -f README.md~