From c2522ce1f50dd5efcf2ab3952a239097b8e3ce59 Mon Sep 17 00:00:00 2001
From: Scott Lahteine <sourcetree@thinkyhead.com>
Date: Sun, 8 May 2016 16:51:33 -0700
Subject: [PATCH 1/3] Fallthru in thermal runaway test when TRState changes

---
 Marlin/temperature.cpp | 23 ++++++++++-------------
 1 file changed, 10 insertions(+), 13 deletions(-)

diff --git a/Marlin/temperature.cpp b/Marlin/temperature.cpp
index f8c85fbc96..a8f9c916ff 100644
--- a/Marlin/temperature.cpp
+++ b/Marlin/temperature.cpp
@@ -1056,24 +1056,21 @@ void Temperature::init() {
         *state = TRInactive;
       // Inactive state waits for a target temperature to be set
       case TRInactive:
-        if (target_temperature > 0) {
-          tr_target_temperature[heater_index] = target_temperature;
-          *state = TRFirstHeating;
-        }
-        break;
+        if (target_temperature <= 0) break;
+        tr_target_temperature[heater_index] = target_temperature;
+        *state = TRFirstHeating;
       // When first heating, wait for the temperature to be reached then go to Stable state
       case TRFirstHeating:
-        if (temperature >= tr_target_temperature[heater_index]) *state = TRStable;
-        break;
+        if (temperature < tr_target_temperature[heater_index]) break;
+        *state = TRStable;
       // While the temperature is stable watch for a bad temperature
       case TRStable:
-        // If the temperature is over the target (-hysteresis) restart the timer
-        if (temperature >= tr_target_temperature[heater_index] - hysteresis_degc)
-          *timer = millis();
-        // If the timer goes too long without a reset, trigger shutdown
-        else if (ELAPSED(millis(), *timer + period_seconds * 1000UL))
+        if (temperature < tr_target_temperature[heater_index] - hysteresis_degc && ELAPSED(millis(), *timer))
           *state = TRRunaway;
-        break;
+        else {
+          *timer = millis() + period_seconds * 1000UL;
+          break;
+        }
       case TRRunaway:
         _temp_error(heater_id, PSTR(MSG_T_THERMAL_RUNAWAY), PSTR(MSG_THERMAL_RUNAWAY));
     }

From 6b13c430ae587c87f3d94485dbb7a16f905196f2 Mon Sep 17 00:00:00 2001
From: Scott Lahteine <sourcetree@thinkyhead.com>
Date: Sun, 8 May 2016 17:01:46 -0700
Subject: [PATCH 2/3] The TRReset state is not needed with fall-through

---
 Marlin/temperature.cpp | 5 +----
 Marlin/temperature.h   | 6 +++---
 2 files changed, 4 insertions(+), 7 deletions(-)

diff --git a/Marlin/temperature.cpp b/Marlin/temperature.cpp
index a8f9c916ff..8879b4737f 100644
--- a/Marlin/temperature.cpp
+++ b/Marlin/temperature.cpp
@@ -1048,12 +1048,9 @@ void Temperature::init() {
 
     // If the target temperature changes, restart
     if (tr_target_temperature[heater_index] != target_temperature)
-      *state = TRReset;
+      *state = TRInactive;
 
     switch (*state) {
-      case TRReset:
-        *timer = 0;
-        *state = TRInactive;
       // Inactive state waits for a target temperature to be set
       case TRInactive:
         if (target_temperature <= 0) break;
diff --git a/Marlin/temperature.h b/Marlin/temperature.h
index 41e4ac16fd..a178f1fed0 100644
--- a/Marlin/temperature.h
+++ b/Marlin/temperature.h
@@ -358,17 +358,17 @@ class Temperature {
 
     #if ENABLED(THERMAL_PROTECTION_HOTENDS) || HAS_THERMALLY_PROTECTED_BED
 
-      typedef enum TRState { TRReset, TRInactive, TRFirstHeating, TRStable, TRRunaway } TRstate;
+      typedef enum TRState { TRInactive, TRFirstHeating, TRStable, TRRunaway } TRstate;
 
       void thermal_runaway_protection(TRState* state, millis_t* timer, float temperature, float target_temperature, int heater_id, int period_seconds, int hysteresis_degc);
 
       #if ENABLED(THERMAL_PROTECTION_HOTENDS)
-        TRState thermal_runaway_state_machine[EXTRUDERS] = { TRReset };
+        TRState thermal_runaway_state_machine[EXTRUDERS] = { TRInactive };
         millis_t thermal_runaway_timer[EXTRUDERS] = { 0 };
       #endif
 
       #if HAS_THERMALLY_PROTECTED_BED
-        TRState thermal_runaway_bed_state_machine = TRReset;
+        TRState thermal_runaway_bed_state_machine = TRInactive;
         millis_t thermal_runaway_bed_timer;
       #endif
 

From 9b92bb8f31217cf785979a7f24ea74f6b574942e Mon Sep 17 00:00:00 2001
From: Scott Lahteine <sourcetree@thinkyhead.com>
Date: Sun, 8 May 2016 17:07:45 -0700
Subject: [PATCH 3/3] Set the initial state based on target temperature

---
 Marlin/temperature.cpp | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/Marlin/temperature.cpp b/Marlin/temperature.cpp
index 8879b4737f..19e66c6742 100644
--- a/Marlin/temperature.cpp
+++ b/Marlin/temperature.cpp
@@ -1047,15 +1047,14 @@ void Temperature::init() {
     int heater_index = heater_id >= 0 ? heater_id : EXTRUDERS;
 
     // If the target temperature changes, restart
-    if (tr_target_temperature[heater_index] != target_temperature)
-      *state = TRInactive;
+    if (tr_target_temperature[heater_index] != target_temperature) {
+      tr_target_temperature[heater_index] = target_temperature;
+      *state = target_temperature > 0 ? TRFirstHeating : TRInactive;
+    }
 
     switch (*state) {
       // Inactive state waits for a target temperature to be set
-      case TRInactive:
-        if (target_temperature <= 0) break;
-        tr_target_temperature[heater_index] = target_temperature;
-        *state = TRFirstHeating;
+      case TRInactive: break;
       // When first heating, wait for the temperature to be reached then go to Stable state
       case TRFirstHeating:
         if (temperature < tr_target_temperature[heater_index]) break;