Cleanup temperature code

- Get rid of unused temp states in the ISR, resulting in more frequent
temperature reading with fewer sensors
- Shrink code slightly in min/max testing

Marlin/temperature.cpp

@@ -1240,16 +1240,26 @@ void disable_heater() {
 enum TempState {
   PrepareTemp_0,
   MeasureTemp_0,
+  #if HAS_TEMP_BED
     PrepareTemp_BED,
     MeasureTemp_BED,
+  #endif
+  #if HAS_TEMP_1
     PrepareTemp_1,
     MeasureTemp_1,
+  #endif
+  #if HAS_TEMP_2
     PrepareTemp_2,
     MeasureTemp_2,
+  #endif
+  #if HAS_TEMP_3
     PrepareTemp_3,
     MeasureTemp_3,
+  #endif
+  #if HAS_FILAMENT_SENSOR
     Prepare_FILWIDTH,
     Measure_FILWIDTH,
+  #endif
   StartupDelay // Startup, delay initial temp reading a tiny bit so the hardware can settle
 };
 
@@ -1473,78 +1483,124 @@ ISR(TIMER0_COMPB_vect) {
       #if HAS_TEMP_0
         raw_temp_value[0] += ADC;
       #endif
-      temp_state = PrepareTemp_BED;
+      temp_state =
+        #if HAS_TEMP_BED
+          PrepareTemp_BED
+        #elif HAS_TEMP_1
+          PrepareTemp_1
+        #elif HAS_TEMP_2
+          PrepareTemp_2
+        #elif HAS_TEMP_3
+          PrepareTemp_3
+        #elif HAS_FILAMENT_SENSOR
+          Prepare_FILWIDTH
+        #else
+          PrepareTemp_0
+        #endif
+      ;
       break;
-    case PrepareTemp_BED:
+
     #if HAS_TEMP_BED
+      case PrepareTemp_BED:
         START_ADC(TEMP_BED_PIN);
-      #endif
         lcd_buttons_update();
         temp_state = MeasureTemp_BED;
         break;
       case MeasureTemp_BED:
-      #if HAS_TEMP_BED
         raw_temp_bed_value += ADC;
+        temp_state =
+          #if HAS_TEMP_1
+            PrepareTemp_1
+          #elif HAS_TEMP_2
+            PrepareTemp_2
+          #elif HAS_TEMP_3
+            PrepareTemp_3
+          #elif HAS_FILAMENT_SENSOR
+            Prepare_FILWIDTH
+          #else
+            PrepareTemp_0
           #endif
-      temp_state = PrepareTemp_1;
+        ;
         break;
-    case PrepareTemp_1:
+    #endif
+
     #if HAS_TEMP_1
+      case PrepareTemp_1:
         START_ADC(TEMP_1_PIN);
-      #endif
         lcd_buttons_update();
         temp_state = MeasureTemp_1;
         break;
       case MeasureTemp_1:
-      #if HAS_TEMP_1
         raw_temp_value[1] += ADC;
+        temp_state =
+          #if HAS_TEMP_2
+            PrepareTemp_2
+          #elif HAS_TEMP_3
+            PrepareTemp_3
+          #elif HAS_FILAMENT_SENSOR
+            Prepare_FILWIDTH
+          #else
+            PrepareTemp_0
           #endif
-      temp_state = PrepareTemp_2;
+        ;
         break;
-    case PrepareTemp_2:
+    #endif
+
     #if HAS_TEMP_2
+      case PrepareTemp_2:
         START_ADC(TEMP_2_PIN);
-      #endif
         lcd_buttons_update();
         temp_state = MeasureTemp_2;
         break;
       case MeasureTemp_2:
-      #if HAS_TEMP_2
         raw_temp_value[2] += ADC;
+        temp_state =
+          #if HAS_TEMP_3
+            PrepareTemp_3
+          #elif HAS_FILAMENT_SENSOR
+            Prepare_FILWIDTH
+          #else
+            PrepareTemp_0
           #endif
-      temp_state = PrepareTemp_3;
+        ;
         break;
-    case PrepareTemp_3:
+    #endif
+
     #if HAS_TEMP_3
+      case PrepareTemp_3:
         START_ADC(TEMP_3_PIN);
-      #endif
         lcd_buttons_update();
         temp_state = MeasureTemp_3;
         break;
       case MeasureTemp_3:
-      #if HAS_TEMP_3
         raw_temp_value[3] += ADC;
+        temp_state =
+          #if HAS_FILAMENT_SENSOR
+            Prepare_FILWIDTH
+          #else
+            PrepareTemp_0
           #endif
-      temp_state = Prepare_FILWIDTH;
+        ;
         break;
-    case Prepare_FILWIDTH:
+    #endif
+
     #if HAS_FILAMENT_SENSOR
+      case Prepare_FILWIDTH:
         START_ADC(FILWIDTH_PIN);
-      #endif
         lcd_buttons_update();
         temp_state = Measure_FILWIDTH;
         break;
       case Measure_FILWIDTH:
-      #if HAS_FILAMENT_SENSOR
         // raw_filwidth_value += ADC;  //remove to use an IIR filter approach
         if (ADC > 102) { //check that ADC is reading a voltage > 0.5 volts, otherwise don't take in the data.
           raw_filwidth_value -= (raw_filwidth_value>>7);  //multiply raw_filwidth_value by 127/128
           raw_filwidth_value += ((unsigned long)ADC<<7);  //add new ADC reading
         }
-      #endif
         temp_state = PrepareTemp_0;
         temp_count++;
         break;
+    #endif
+
     case StartupDelay:
       temp_state = PrepareTemp_0;
       break;
@@ -1587,44 +1643,39 @@ ISR(TIMER0_COMPB_vect) {
 
     #if HEATER_0_RAW_LO_TEMP > HEATER_0_RAW_HI_TEMP
       #define GE0 <=
-      #define LE0 >=
     #else
       #define GE0 >=
-      #define LE0 <=
     #endif
     if (current_temperature_raw[0] GE0 maxttemp_raw[0]) max_temp_error(0);
-    if (current_temperature_raw[0] LE0 minttemp_raw[0]) min_temp_error(0);
+    if (minttemp_raw[0] GE0 current_temperature_raw[0]) min_temp_error(0);
 
     #if EXTRUDERS > 1
       #if HEATER_1_RAW_LO_TEMP > HEATER_1_RAW_HI_TEMP
         #define GE1 <=
-        #define LE1 >=
       #else
         #define GE1 >=
-        #define LE1 <=
       #endif
       if (current_temperature_raw[1] GE1 maxttemp_raw[1]) max_temp_error(1);
-      if (current_temperature_raw[1] LE1 minttemp_raw[1]) min_temp_error(1);
+      if (minttemp_raw[1] GE0 current_temperature_raw[1]) min_temp_error(1);
+
       #if EXTRUDERS > 2
         #if HEATER_2_RAW_LO_TEMP > HEATER_2_RAW_HI_TEMP
           #define GE2 <=
-          #define LE2 >=
         #else
           #define GE2 >=
-          #define LE2 <=
         #endif
         if (current_temperature_raw[2] GE2 maxttemp_raw[2]) max_temp_error(2);
-        if (current_temperature_raw[2] LE2 minttemp_raw[2]) min_temp_error(2);
+        if (minttemp_raw[2] GE0 current_temperature_raw[2]) min_temp_error(2);
+
         #if EXTRUDERS > 3
           #if HEATER_3_RAW_LO_TEMP > HEATER_3_RAW_HI_TEMP
             #define GE3 <=
-            #define LE3 >=
           #else
             #define GE3 >=
-            #define LE3 <=
           #endif
           if (current_temperature_raw[3] GE3 maxttemp_raw[3]) max_temp_error(3);
-          if (current_temperature_raw[3] LE3 minttemp_raw[3]) min_temp_error(3);
+          if (minttemp_raw[3] GE0 current_temperature_raw[3]) min_temp_error(3);
+
         #endif // EXTRUDERS > 3
       #endif // EXTRUDERS > 2
     #endif // EXTRUDERS > 1
@@ -1632,10 +1683,8 @@ ISR(TIMER0_COMPB_vect) {
     #if defined(BED_MAXTEMP) && (TEMP_SENSOR_BED != 0)
       #if HEATER_BED_RAW_LO_TEMP > HEATER_BED_RAW_HI_TEMP
         #define GEBED <=
-        #define LEBED >=
       #else
         #define GEBED >=
-        #define LEBED <=
       #endif
       if (current_temperature_bed_raw GEBED bed_maxttemp_raw) {
         target_temperature_bed = 0;