From 56ca47ab9d3e4c3c5711995f80a50c7d5f84d7e4 Mon Sep 17 00:00:00 2001
From: Scott Lahteine <github@thinkyhead.com>
Date: Sun, 7 May 2017 21:32:01 -0500
Subject: [PATCH] Patch configuration temp units

---
 Marlin/Marlin_main.cpp         | 19 +++++++++++++++----
 Marlin/configuration_store.cpp |  4 ++--
 2 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/Marlin/Marlin_main.cpp b/Marlin/Marlin_main.cpp
index e470fc88f7..8a174aeb7b 100644
--- a/Marlin/Marlin_main.cpp
+++ b/Marlin/Marlin_main.cpp
@@ -1298,19 +1298,30 @@ inline bool code_value_bool() { return !code_has_value() || code_value_byte() >
 #if ENABLED(TEMPERATURE_UNITS_SUPPORT)
   inline void set_input_temp_units(TempUnit units) { input_temp_units = units; }
 
-  float temp_abs(const float &c) {
+  float to_temp_units(const float &c) {
     switch (input_temp_units) {
       case TEMPUNIT_F:
-        return (c - 32.0) * 0.5555555556;
+        return c * 0.5555555556 + 32.0;
       case TEMPUNIT_K:
-        return c - 273.15;
+        return c + 273.15;
       case TEMPUNIT_C:
       default:
         return c;
     }
   }
 
-  int16_t code_value_temp_abs() { return temp_abs(code_value_float()); }
+  int16_t code_value_temp_abs() {
+    const float c = code_value_float();
+    switch (input_temp_units) {
+      case TEMPUNIT_F:
+        return (int16_t)((c - 32.0) * 0.5555555556);
+      case TEMPUNIT_K:
+        return (int16_t)(c - 273.15);
+      case TEMPUNIT_C:
+      default:
+        return (int16_t)(c);
+    }
+  }
 
   int16_t code_value_temp_diff() {
     switch (input_temp_units) {
diff --git a/Marlin/configuration_store.cpp b/Marlin/configuration_store.cpp
index ef7e040147..99495997b8 100644
--- a/Marlin/configuration_store.cpp
+++ b/Marlin/configuration_store.cpp
@@ -1257,8 +1257,8 @@ void MarlinSettings::reset() {
       CONFIG_ECHO_START;
       #if ENABLED(TEMPERATURE_UNITS_SUPPORT)
         extern TempUnit input_temp_units;
-        extern float temp_abs(const float &f);
-        #define TEMP_UNIT(N) temp_abs(N)
+        extern float to_temp_units(const float &f);
+        #define TEMP_UNIT(N) to_temp_units(N)
         SERIAL_ECHOPGM("  M149 ");
         SERIAL_CHAR(input_temp_units == TEMPUNIT_K ? 'K' : input_temp_units == TEMPUNIT_F ? 'F' : 'C');
         SERIAL_ECHOPGM(" ; Units in ");