diff --git a/config/board.3drag.h b/config/board.3drag.h
index ee1cc96..a8528cd 100644
--- a/config/board.3drag.h
+++ b/config/board.3drag.h
@@ -211,6 +211,9 @@ DEFINE_TEMP_SENSOR(bed,      TT_THERMISTOR, AIO14, THERMISTOR_BED)
   are defined or the order of the definitions differs. The first defined
   device has the index 0 (zero).
 
+  Set 'invert' to 0 for normal heaters. Setting it to 1 inverts the pin signal
+  for this pin, e.g. for a MOSFET with a driver.
+
   Set 'pwm' to ...
     1  for using PWM on a PWM-able pin and on/off on other pins.
     0  for using on/off on a PWM-able pin, too.
@@ -220,10 +223,10 @@ DEFINE_TEMP_SENSOR(bed,      TT_THERMISTOR, AIO14, THERMISTOR_BED)
   influenced globally with FAST_PWM, see below.
 */
 //DEFINE_HEATERS_START
-//            name      port   pwm
-DEFINE_HEATER(extruder, DIO10, 1)
-DEFINE_HEATER(bed,      DIO9,  1)
-DEFINE_HEATER(fan,      DIO8,  1)
+//            name      pin      invert  pwm
+DEFINE_HEATER(extruder, DIO10,   0,      1)
+DEFINE_HEATER(bed,      DIO9,    0,      1)
+DEFINE_HEATER(fan,      DIO8,    0,      1)
 
 #define HEATER_EXTRUDER HEATER_extruder
 #define HEATER_BED HEATER_bed
diff --git a/config/board.cnc-shield-v3.h b/config/board.cnc-shield-v3.h
index 42d0d47..1c30c21 100644
--- a/config/board.cnc-shield-v3.h
+++ b/config/board.cnc-shield-v3.h
@@ -211,6 +211,9 @@ DEFINE_TEMP_SENSOR(extruder, TT_THERMISTOR, AIO3,  THERMISTOR_EXTRUDER)
   are defined or the order of the definitions differs. The first defined
   device has the index 0 (zero).
 
+  Set 'invert' to 0 for normal heaters. Setting it to 1 inverts the pin signal
+  for this pin, e.g. for a MOSFET with a driver.
+
   Set 'pwm' to ...
     1  for using PWM on a PWM-able pin and on/off on other pins.
     0  for using on/off on a PWM-able pin, too.
@@ -220,8 +223,8 @@ DEFINE_TEMP_SENSOR(extruder, TT_THERMISTOR, AIO3,  THERMISTOR_EXTRUDER)
   influenced globally with FAST_PWM, see below.
 */
 //DEFINE_HEATERS_START
-//            name      port   pwm
-DEFINE_HEATER(extruder, AIO2,  1)
+//            name      pin      invert  pwm
+DEFINE_HEATER(extruder, AIO2,    0,      1)
 
 #define HEATER_EXTRUDER HEATER_extruder
 //DEFINE_HEATERS_END
diff --git a/config/board.gen3.h b/config/board.gen3.h
index 46436eb..2c5a0f2 100644
--- a/config/board.gen3.h
+++ b/config/board.gen3.h
@@ -204,6 +204,9 @@ DEFINE_TEMP_SENSOR(noheater, TT_INTERCOM,   AIO0,  0)
   are defined or the order of the definitions differs. The first defined
   device has the index 0 (zero).
 
+  Set 'invert' to 0 for normal heaters. Setting it to 1 inverts the pin signal
+  for this pin, e.g. for a MOSFET with a driver.
+
   Set 'pwm' to ...
     1  for using PWM on a PWM-able pin and on/off on other pins.
     0  for using on/off on a PWM-able pin, too.
@@ -213,7 +216,7 @@ DEFINE_TEMP_SENSOR(noheater, TT_INTERCOM,   AIO0,  0)
   influenced globally with FAST_PWM, see below.
 */
 //DEFINE_HEATERS_START
-//            name      port   pwm
+//            name      pin      invert  pwm
 
 //DEFINE_HEATERS_END
 
diff --git a/config/board.gen6.h b/config/board.gen6.h
index 3b00851..9c5630e 100644
--- a/config/board.gen6.h
+++ b/config/board.gen6.h
@@ -206,6 +206,9 @@ DEFINE_TEMP_SENSOR(extruder, TT_THERMISTOR, AIO5,  THERMISTOR_EXTRUDER)
   are defined or the order of the definitions differs. The first defined
   device has the index 0 (zero).
 
+  Set 'invert' to 0 for normal heaters. Setting it to 1 inverts the pin signal
+  for this pin, e.g. for a MOSFET with a driver.
+
   Set 'pwm' to ...
     1  for using PWM on a PWM-able pin and on/off on other pins.
     0  for using on/off on a PWM-able pin, too.
@@ -215,8 +218,8 @@ DEFINE_TEMP_SENSOR(extruder, TT_THERMISTOR, AIO5,  THERMISTOR_EXTRUDER)
   influenced globally with FAST_PWM, see below.
 */
 //DEFINE_HEATERS_START
-//            name      port   pwm
-DEFINE_HEATER(extruder, DIO6,  1)
+//            name      pin      invert  pwm
+DEFINE_HEATER(extruder, DIO6,    0,      1)
 
 #define HEATER_EXTRUDER HEATER_extruder
 //DEFINE_HEATERS_END
diff --git a/config/board.gen7-arm.h b/config/board.gen7-arm.h
index fe9fc26..62a2668 100644
--- a/config/board.gen7-arm.h
+++ b/config/board.gen7-arm.h
@@ -164,7 +164,7 @@
 //DEFINE_TEMP_SENSORS_START
 //                 name      type           pin    additional
 DEFINE_TEMP_SENSOR(extruder, TT_THERMISTOR, PIO1_0,THERMISTOR_EXTRUDER)
-//DEFINE_TEMP_SENSOR(bed,      TT_THERMISTOR, PIO1_1,THERMISTOR_BED)
+DEFINE_TEMP_SENSOR(bed,      TT_THERMISTOR, PIO1_1,THERMISTOR_BED)
 
 // Beta algorithm      r0      beta  r2    vadc
 // Steinhart-Hart      rp      t0    r0      t1    r1      t2    r2
@@ -210,6 +210,9 @@ DEFINE_TEMP_SENSOR(extruder, TT_THERMISTOR, PIO1_0,THERMISTOR_EXTRUDER)
   are defined or the order of the definitions differs. The first defined
   device has the index 0 (zero).
 
+  Set 'invert' to 0 for normal heaters. Setting it to 1 inverts the pin signal
+  for this pin, e.g. for a MOSFET with a driver.
+
   Set 'pwm' to ...
     frequency  in Hertz (Hz) on ARM based controllers to set PWM frequency of
                this pin's output. Frequency isn't always accurate, Teacup
@@ -228,12 +231,12 @@ DEFINE_TEMP_SENSOR(extruder, TT_THERMISTOR, PIO1_0,THERMISTOR_EXTRUDER)
   Pins which don't allow PWM are always operated in on/off mode.
 */
 //DEFINE_HEATERS_START
-//            name      port   pwm
-DEFINE_HEATER(extruder, PIO0_10, 20000)
-//DEFINE_HEATER(bed,      PIO0_11, 10)
+//            name      pin      invert  pwm
+DEFINE_HEATER(extruder, PIO0_10, 0,      20000)
+DEFINE_HEATER(bed,      PIO0_11, 1,      10)
 
 #define HEATER_EXTRUDER HEATER_extruder
-//#define HEATER_BED HEATER_bed
+#define HEATER_BED HEATER_bed
 //DEFINE_HEATERS_END
 
 
diff --git a/config/board.gen7-v1.1-v1.3.h b/config/board.gen7-v1.1-v1.3.h
index aa77a20..db3387e 100644
--- a/config/board.gen7-v1.1-v1.3.h
+++ b/config/board.gen7-v1.1-v1.3.h
@@ -215,6 +215,9 @@ DEFINE_TEMP_SENSOR(bed,      TT_THERMISTOR, AIO2,  THERMISTOR_BED)
   are defined or the order of the definitions differs. The first defined
   device has the index 0 (zero).
 
+  Set 'invert' to 0 for normal heaters. Setting it to 1 inverts the pin signal
+  for this pin, e.g. for a MOSFET with a driver.
+
   Set 'pwm' to ...
     1  for using PWM on a PWM-able pin and on/off on other pins.
     0  for using on/off on a PWM-able pin, too.
@@ -224,9 +227,9 @@ DEFINE_TEMP_SENSOR(bed,      TT_THERMISTOR, AIO2,  THERMISTOR_BED)
   influenced globally with FAST_PWM, see below.
 */
 //DEFINE_HEATERS_START
-//            name      port   pwm
-DEFINE_HEATER(extruder, DIO4,  1)
-DEFINE_HEATER(bed,      DIO3,  1)
+//            name      pin      invert  pwm
+DEFINE_HEATER(extruder, DIO4,    0,      1)
+DEFINE_HEATER(bed,      DIO3,    0,      1)
 
 #define HEATER_EXTRUDER HEATER_extruder
 #define HEATER_BED HEATER_bed
diff --git a/config/board.gen7-v1.4.h b/config/board.gen7-v1.4.h
index fc58d84..93df06e 100644
--- a/config/board.gen7-v1.4.h
+++ b/config/board.gen7-v1.4.h
@@ -216,6 +216,9 @@ DEFINE_TEMP_SENSOR(bed,      TT_THERMISTOR, AIO0,  THERMISTOR_BED)
   are defined or the order of the definitions differs. The first defined
   device has the index 0 (zero).
 
+  Set 'invert' to 0 for normal heaters. Setting it to 1 inverts the pin signal
+  for this pin, e.g. for a MOSFET with a driver.
+
   Set 'pwm' to ...
     1  for using PWM on a PWM-able pin and on/off on other pins.
     0  for using on/off on a PWM-able pin, too.
@@ -225,9 +228,9 @@ DEFINE_TEMP_SENSOR(bed,      TT_THERMISTOR, AIO0,  THERMISTOR_BED)
   influenced globally with FAST_PWM, see below.
 */
 //DEFINE_HEATERS_START
-//            name      port   pwm
-DEFINE_HEATER(extruder, DIO4,  1)
-DEFINE_HEATER(bed,      DIO3,  1)
+//            name      pin      invert  pwm
+DEFINE_HEATER(extruder, DIO4,    0,      1)
+DEFINE_HEATER(bed,      DIO3,    0,      1)
 
 #define HEATER_EXTRUDER HEATER_extruder
 #define HEATER_BED HEATER_bed
diff --git a/config/board.nanoheart-v1.0.h b/config/board.nanoheart-v1.0.h
index a17f59b..07f2bb7 100644
--- a/config/board.nanoheart-v1.0.h
+++ b/config/board.nanoheart-v1.0.h
@@ -213,6 +213,9 @@ DEFINE_TEMP_SENSOR(bed,      TT_THERMISTOR, AIO7,  THERMISTOR_BED)
   are defined or the order of the definitions differs. The first defined
   device has the index 0 (zero).
 
+  Set 'invert' to 0 for normal heaters. Setting it to 1 inverts the pin signal
+  for this pin, e.g. for a MOSFET with a driver.
+
   Set 'pwm' to ...
     1  for using PWM on a PWM-able pin and on/off on other pins.
     0  for using on/off on a PWM-able pin, too.
@@ -222,9 +225,9 @@ DEFINE_TEMP_SENSOR(bed,      TT_THERMISTOR, AIO7,  THERMISTOR_BED)
   influenced globally with FAST_PWM, see below.
 */
 //DEFINE_HEATERS_START
-//            name      port   pwm
-DEFINE_HEATER(extruder, DIO11, 1)
-DEFINE_HEATER(bed,      DIO3,  1)
+//            name      pin      invert  pwm
+DEFINE_HEATER(extruder, DIO11,   0,      1)
+DEFINE_HEATER(bed,      DIO3,    0,      1)
 
 #define HEATER_EXTRUDER HEATER_extruder
 #define HEATER_BED HEATER_bed
diff --git a/config/board.ramps-v1.2.h b/config/board.ramps-v1.2.h
index b1e5336..2d2eac4 100644
--- a/config/board.ramps-v1.2.h
+++ b/config/board.ramps-v1.2.h
@@ -212,6 +212,9 @@ DEFINE_TEMP_SENSOR(bed,      TT_THERMISTOR, AIO1,  THERMISTOR_BED)
   are defined or the order of the definitions differs. The first defined
   device has the index 0 (zero).
 
+  Set 'invert' to 0 for normal heaters. Setting it to 1 inverts the pin signal
+  for this pin, e.g. for a MOSFET with a driver.
+
   Set 'pwm' to ...
     1  for using PWM on a PWM-able pin and on/off on other pins.
     0  for using on/off on a PWM-able pin, too.
@@ -221,10 +224,10 @@ DEFINE_TEMP_SENSOR(bed,      TT_THERMISTOR, AIO1,  THERMISTOR_BED)
   influenced globally with FAST_PWM, see below.
 */
 //DEFINE_HEATERS_START
-//            name      port   pwm
-DEFINE_HEATER(extruder, DIO10, 1)
-DEFINE_HEATER(bed,      DIO8,  1)
-DEFINE_HEATER(fan,      DIO9,  1)
+//            name      pin      invert  pwm
+DEFINE_HEATER(extruder, DIO10,   0,      1)
+DEFINE_HEATER(bed,      DIO8,    0,      1)
+DEFINE_HEATER(fan,      DIO9,    0,      1)
 
 #define HEATER_EXTRUDER HEATER_extruder
 #define HEATER_BED HEATER_bed
diff --git a/config/board.ramps-v1.3.h b/config/board.ramps-v1.3.h
index 255a7bf..5191ccc 100644
--- a/config/board.ramps-v1.3.h
+++ b/config/board.ramps-v1.3.h
@@ -215,6 +215,9 @@ DEFINE_TEMP_SENSOR(bed,      TT_THERMISTOR, AIO14, THERMISTOR_BED)
   are defined or the order of the definitions differs. The first defined
   device has the index 0 (zero).
 
+  Set 'invert' to 0 for normal heaters. Setting it to 1 inverts the pin signal
+  for this pin, e.g. for a MOSFET with a driver.
+
   Set 'pwm' to ...
     1  for using PWM on a PWM-able pin and on/off on other pins.
     0  for using on/off on a PWM-able pin, too.
@@ -224,10 +227,10 @@ DEFINE_TEMP_SENSOR(bed,      TT_THERMISTOR, AIO14, THERMISTOR_BED)
   influenced globally with FAST_PWM, see below.
 */
 //DEFINE_HEATERS_START
-//            name      port   pwm
-DEFINE_HEATER(extruder, DIO10, 1)
-DEFINE_HEATER(bed,      DIO8,  1)
-DEFINE_HEATER(fan,      DIO9,  1)
+//            name      pin      invert  pwm
+DEFINE_HEATER(extruder, DIO10,   0,      1)
+DEFINE_HEATER(bed,      DIO8,    0,      1)
+DEFINE_HEATER(fan,      DIO9,    0,      1)
 
 #define HEATER_EXTRUDER HEATER_extruder
 #define HEATER_BED HEATER_bed
diff --git a/config/board.rumba.h b/config/board.rumba.h
index c97cf90..766b134 100644
--- a/config/board.rumba.h
+++ b/config/board.rumba.h
@@ -215,6 +215,9 @@ DEFINE_TEMP_SENSOR(bed,      TT_THERMISTOR, AIO11, THERMISTOR_BED)
   are defined or the order of the definitions differs. The first defined
   device has the index 0 (zero).
 
+  Set 'invert' to 0 for normal heaters. Setting it to 1 inverts the pin signal
+  for this pin, e.g. for a MOSFET with a driver.
+
   Set 'pwm' to ...
     1  for using PWM on a PWM-able pin and on/off on other pins.
     0  for using on/off on a PWM-able pin, too.
@@ -224,10 +227,10 @@ DEFINE_TEMP_SENSOR(bed,      TT_THERMISTOR, AIO11, THERMISTOR_BED)
   influenced globally with FAST_PWM, see below.
 */
 //DEFINE_HEATERS_START
-//            name      port   pwm
-DEFINE_HEATER(extruder, DIO2,  1)
-DEFINE_HEATER(bed,      DIO9,  1)
-DEFINE_HEATER(fan,      DIO8,  1)
+//            name      pin      invert  pwm
+DEFINE_HEATER(extruder, DIO2,    0,      1)
+DEFINE_HEATER(bed,      DIO9,    0,      1)
+DEFINE_HEATER(fan,      DIO8,    0,      1)
 
 #define HEATER_EXTRUDER HEATER_extruder
 #define HEATER_BED HEATER_bed
diff --git a/config/board.sanguinololu-v1.1.h b/config/board.sanguinololu-v1.1.h
index ab512a3..31d66a2 100644
--- a/config/board.sanguinololu-v1.1.h
+++ b/config/board.sanguinololu-v1.1.h
@@ -213,6 +213,9 @@ DEFINE_TEMP_SENSOR(bed,      TT_THERMISTOR, AIO6,  THERMISTOR_BED)
   are defined or the order of the definitions differs. The first defined
   device has the index 0 (zero).
 
+  Set 'invert' to 0 for normal heaters. Setting it to 1 inverts the pin signal
+  for this pin, e.g. for a MOSFET with a driver.
+
   Set 'pwm' to ...
     1  for using PWM on a PWM-able pin and on/off on other pins.
     0  for using on/off on a PWM-able pin, too.
@@ -222,9 +225,9 @@ DEFINE_TEMP_SENSOR(bed,      TT_THERMISTOR, AIO6,  THERMISTOR_BED)
   influenced globally with FAST_PWM, see below.
 */
 //DEFINE_HEATERS_START
-//            name      port   pwm
-DEFINE_HEATER(extruder, DIO13, 1)
-DEFINE_HEATER(bed,      DIO14, 1)
+//            name      pin      invert  pwm
+DEFINE_HEATER(extruder, DIO13,   0,      1)
+DEFINE_HEATER(bed,      DIO14,   0,      1)
 
 #define HEATER_EXTRUDER HEATER_extruder
 #define HEATER_BED HEATER_bed
diff --git a/config/board.sanguinololu-v1.2.h b/config/board.sanguinololu-v1.2.h
index c287539..ebca784 100644
--- a/config/board.sanguinololu-v1.2.h
+++ b/config/board.sanguinololu-v1.2.h
@@ -213,6 +213,9 @@ DEFINE_TEMP_SENSOR(bed,      TT_THERMISTOR, AIO6,  THERMISTOR_BED)
   are defined or the order of the definitions differs. The first defined
   device has the index 0 (zero).
 
+  Set 'invert' to 0 for normal heaters. Setting it to 1 inverts the pin signal
+  for this pin, e.g. for a MOSFET with a driver.
+
   Set 'pwm' to ...
     1  for using PWM on a PWM-able pin and on/off on other pins.
     0  for using on/off on a PWM-able pin, too.
@@ -222,9 +225,9 @@ DEFINE_TEMP_SENSOR(bed,      TT_THERMISTOR, AIO6,  THERMISTOR_BED)
   influenced globally with FAST_PWM, see below.
 */
 //DEFINE_HEATERS_START
-//            name      port   pwm
-DEFINE_HEATER(extruder, DIO12, 1)
-DEFINE_HEATER(bed,      DIO13, 1)
+//            name      pin      invert  pwm
+DEFINE_HEATER(extruder, DIO12,   0,      1)
+DEFINE_HEATER(bed,      DIO13,   0,      1)
 
 #define HEATER_EXTRUDER HEATER_extruder
 #define HEATER_BED HEATER_bed
diff --git a/config/board.sanguish.h b/config/board.sanguish.h
index e60dc24..0514d3a 100644
--- a/config/board.sanguish.h
+++ b/config/board.sanguish.h
@@ -213,6 +213,9 @@ DEFINE_TEMP_SENSOR(bed,      TT_THERMISTOR, AIO0,  THERMISTOR_BED)
   are defined or the order of the definitions differs. The first defined
   device has the index 0 (zero).
 
+  Set 'invert' to 0 for normal heaters. Setting it to 1 inverts the pin signal
+  for this pin, e.g. for a MOSFET with a driver.
+
   Set 'pwm' to ...
     1  for using PWM on a PWM-able pin and on/off on other pins.
     0  for using on/off on a PWM-able pin, too.
@@ -222,9 +225,9 @@ DEFINE_TEMP_SENSOR(bed,      TT_THERMISTOR, AIO0,  THERMISTOR_BED)
   influenced globally with FAST_PWM, see below.
 */
 //DEFINE_HEATERS_START
-//            name      port   pwm
-DEFINE_HEATER(extruder, DIO3,  1)
-DEFINE_HEATER(bed,      DIO4,  1)
+//            name      pin      invert  pwm
+DEFINE_HEATER(extruder, DIO3,    0,      1)
+DEFINE_HEATER(bed,      DIO4,    0,      1)
 
 #define HEATER_EXTRUDER HEATER_extruder
 #define HEATER_BED HEATER_bed
diff --git a/config/board.teensy++-v2.0.h b/config/board.teensy++-v2.0.h
index fde084c..906454b 100644
--- a/config/board.teensy++-v2.0.h
+++ b/config/board.teensy++-v2.0.h
@@ -211,6 +211,9 @@ DEFINE_TEMP_SENSOR(bed,      TT_THERMISTOR, AIO6,  THERMISTOR_BED)
   are defined or the order of the definitions differs. The first defined
   device has the index 0 (zero).
 
+  Set 'invert' to 0 for normal heaters. Setting it to 1 inverts the pin signal
+  for this pin, e.g. for a MOSFET with a driver.
+
   Set 'pwm' to ...
     1  for using PWM on a PWM-able pin and on/off on other pins.
     0  for using on/off on a PWM-able pin, too.
@@ -220,10 +223,10 @@ DEFINE_TEMP_SENSOR(bed,      TT_THERMISTOR, AIO6,  THERMISTOR_BED)
   influenced globally with FAST_PWM, see below.
 */
 //DEFINE_HEATERS_START
-//            name      port   pwm
-DEFINE_HEATER(extruder, DIO15, 1)
-DEFINE_HEATER(bed,      DIO14, 1)
-DEFINE_HEATER(fan,      DIO16, 0)
+//            name      pin      invert  pwm
+DEFINE_HEATER(extruder, DIO15,   0,      1)
+DEFINE_HEATER(bed,      DIO14,   0,      1)
+DEFINE_HEATER(fan,      DIO16,   0,      0)
 
 #define HEATER_EXTRUDER HEATER_extruder
 #define HEATER_BED HEATER_bed
diff --git a/config/board.teensy-v2.0.h b/config/board.teensy-v2.0.h
index 4d2200c..2f27d50 100644
--- a/config/board.teensy-v2.0.h
+++ b/config/board.teensy-v2.0.h
@@ -211,6 +211,9 @@ DEFINE_TEMP_SENSOR(bed,      TT_THERMISTOR, AIO0,  THERMISTOR_BED)
   are defined or the order of the definitions differs. The first defined
   device has the index 0 (zero).
 
+  Set 'invert' to 0 for normal heaters. Setting it to 1 inverts the pin signal
+  for this pin, e.g. for a MOSFET with a driver.
+
   Set 'pwm' to ...
     1  for using PWM on a PWM-able pin and on/off on other pins.
     0  for using on/off on a PWM-able pin, too.
@@ -220,10 +223,10 @@ DEFINE_TEMP_SENSOR(bed,      TT_THERMISTOR, AIO0,  THERMISTOR_BED)
   influenced globally with FAST_PWM, see below.
 */
 //DEFINE_HEATERS_START
-//            name      port   pwm
-DEFINE_HEATER(extruder, DIO10, 1)
-DEFINE_HEATER(bed,      DIO9,  1)
-DEFINE_HEATER(fan,      DIO8,  0)
+//            name      pin      invert  pwm
+DEFINE_HEATER(extruder, DIO10,   0,      1)
+DEFINE_HEATER(bed,      DIO9,    0,      1)
+DEFINE_HEATER(fan,      DIO8,    0,      0)
 
 #define HEATER_EXTRUDER HEATER_extruder
 #define HEATER_BED HEATER_bed
diff --git a/configtool/addheaterdlg.py b/configtool/addheaterdlg.py
index c7d2924..753ea16 100644
--- a/configtool/addheaterdlg.py
+++ b/configtool/addheaterdlg.py
@@ -5,7 +5,7 @@ from configtool.data import BSIZESMALL, offsetChLabel, offsetTcLabel
 
 class AddHeaterDlg(wx.Dialog):
   def __init__(self, parent, names, pins, font,
-               name = "", pin = "", pwm = "1"):
+               name = "", pin = "", invert = "0", pwm = "1"):
     wx.Dialog.__init__(self, parent, wx.ID_ANY, "Add heater", size = (400, 204))
     self.SetFont(font)
     self.Bind(wx.EVT_CLOSE, self.onCancel)
@@ -54,6 +54,13 @@ class AddHeaterDlg(wx.Dialog):
 
     gsz.Add(lsz, pos = (3, 1))
 
+    self.cbInv = wx.CheckBox(self, wx.ID_ANY, "Invert")
+    self.cbInv.SetFont(font)
+    self.cbInv.SetValue(int(invert) != 0)
+    self.cbInv.SetToolTipString("Invert the pin signal.")
+
+    gsz.Add(self.cbInv, pos = (3, 3))
+
     self.cbPwm = wx.CheckBox(self, wx.ID_ANY, "PWM")
     self.cbPwm.SetFont(font)
     self.cbPwm.SetValue(int(pwm) != 0)
@@ -120,12 +127,18 @@ class AddHeaterDlg(wx.Dialog):
   def getValues(self):
     nm = self.tcName.GetValue()
     pin = self.choices[self.chPin.GetSelection()]
+
+    if self.cbInv.IsChecked():
+      invert = "1"
+    else:
+      invert = "0"
+
     if self.cbPwm.IsChecked():
       pwm = "1"
     else:
       pwm = "0"
 
-    return (nm, pin, pwm)
+    return (nm, pin, invert, pwm)
 
   def onSave(self, evt):
     self.EndModal(wx.ID_OK)
diff --git a/configtool/board.generic.h b/configtool/board.generic.h
index 071f8a1..aa5004a 100644
--- a/configtool/board.generic.h
+++ b/configtool/board.generic.h
@@ -207,6 +207,9 @@
   are defined or the order of the definitions differs. The first defined
   device has the index 0 (zero).
 
+  Set 'invert' to 0 for normal heaters. Setting it to 1 inverts the pin signal
+  for this pin, e.g. for a MOSFET with a driver.
+
   Set 'pwm' to ...
     1  for using PWM on a PWM-able pin and on/off on other pins.
     0  for using on/off on a PWM-able pin, too.
diff --git a/configtool/boardpanel.py b/configtool/boardpanel.py
index 286a06e..de9cf4a 100644
--- a/configtool/boardpanel.py
+++ b/configtool/boardpanel.py
@@ -13,7 +13,7 @@ from configtool.data import (defineValueFormat,
                              reCandProcessors, reCandCPUClocks, reFloatAttr,
                              reDefine, reDefineBL, reDefQS, reDefQSm,
                              reDefQSm2, reDefBool, reDefBoolBL, reDefHT,
-                             reDefTS, reDefTT, reSensor, reHeater,
+                             reDefTS, reDefTT, reSensor, reHeater3, reHeater4,
                              reTempTable4, reTempTable7)
 from configtool.pinoutspage import PinoutsPage
 from configtool.sensorpage import SensorsPage
@@ -468,11 +468,20 @@ class BoardPanel(wx.Panel):
     return None
 
   def parseHeater(self, s):
-    m = reHeater.search(s)
+    m = reHeater4.search(s)
+    if m:
+      t = m.groups()
+      if len(t) == 4:
+        return list(t)
+    # reHeater3 deprecated, for compatibility with old config files only.
+    m = reHeater3.search(s)
     if m:
       t = m.groups()
       if len(t) == 3:
-        return list(t)
+        t = list(t)
+        t.insert(2, '0')
+        return t
+    # End of deprecated part.
     return None
 
   def parseTempTable(self, s):
@@ -604,9 +613,10 @@ class BoardPanel(wx.Panel):
       m = reStartHeaters.match(ln)
       if m:
         fp.write(ln)
-        fp.write("//            name      port   pwm\n")
+        fp.write("//            name      pin      invert  pwm\n")
         for s in self.heaters:
-          sstr = "%-10s%-7s%s" % ((s[0] + ","), (s[1] + ","), s[2])
+          sstr = "%-10s%-9s%-8s%s" % ((s[0] + ","), (s[1] + ","),
+                                      (s[2] + ","), s[3])
           fp.write("DEFINE_HEATER(%s)\n" % sstr)
         fp.write("\n")
         for s in self.heaters:
diff --git a/configtool/data.py b/configtool/data.py
index 1086f86..eb5742a 100644
--- a/configtool/data.py
+++ b/configtool/data.py
@@ -57,7 +57,9 @@ reHelpTextEnd = re.compile("^\s*\*/")
 reHelpText = re.compile("/\*\*.*?\*/\r?\n", re.DOTALL)
 
 reSensor = re.compile(".*\\(\s*(\w+)\s*,\s*(\w+)\s*,\s*(\w+)\s*,\s*(\w+)\s*\\)")
-reHeater = re.compile(".*\\(\s*(\w+)\s*,\s*(\w+)\s*,\s*(\w+)\s*\\)")
+# reHeater3 deprecated, for compatibility with old config files only.
+reHeater3 = re.compile(".*\\(\s*(\w+)\s*,\s*(\w+)\s*,\s*(\w+)\s*\\)")
+reHeater4 = re.compile(".*\\(\s*(\w+)\s*,\s*(\w+)\s*,\s*(\w+)\s*,\s*(\w+)\s*\\)")
 reTempTable4 = re.compile(".*\\(\s*(\d+)\s*,\s*(\d+)\s*,\s*(\d+)\s*,\s*(\d*.?\d*)\s*\\)")
 reTempTable7 = re.compile(".*\\(\s*(\d+)\s*,\s*(\d*.?\d*)\s*,\s*(\d+)\s*,\s*(\d*.?\d*)\s*,\s*(\d+)\s*,\s*(\d*.?\d*)\s*,\s*(\d+)\s*\\)")
 
diff --git a/configtool/heaterlist.py b/configtool/heaterlist.py
index 2b709a3..094c9c5 100644
--- a/configtool/heaterlist.py
+++ b/configtool/heaterlist.py
@@ -7,7 +7,7 @@ class HeaterList(wx.ListCtrl):
     self.parent = parent
     self.currentItem = None
     wx.ListCtrl.__init__(self, parent, wx.ID_ANY,
-                         size = (95 + 55 + 55 + 4, 100),
+                         size = (95 + 75 + 55 + 55 + 4, 100),
                          style = wx.LC_REPORT | wx.LC_VIRTUAL | wx.LC_HRULES |
                          wx.LC_VRULES)
     self.SetFont(font)
@@ -17,10 +17,12 @@ class HeaterList(wx.ListCtrl):
 
     self.InsertColumn(0, "Name")
     self.InsertColumn(1, "Pin")
-    self.InsertColumn(2, "PWM")
+    self.InsertColumn(2, "Invert")
+    self.InsertColumn(3, "PWM")
     self.SetColumnWidth(0, 95)
-    self.SetColumnWidth(1, 55)
+    self.SetColumnWidth(1, 75)
     self.SetColumnWidth(2, 55)
+    self.SetColumnWidth(3, 55)
 
     self.SetItemCount(0)
 
@@ -64,7 +66,7 @@ class HeaterList(wx.ListCtrl):
 
   def OnGetItemText(self, item, col):
     if item < 0 or item >= len(self.heaterList):
-      return "Error - no heaters"
+      return "Error - no heaters."
 
     s = self.heaterList[item]
 
@@ -77,3 +79,8 @@ class HeaterList(wx.ListCtrl):
         return "True"
       else:
         return "False"
+    elif col == 3:
+      if int(s[3]):
+        return "True"
+      else:
+        return "False"
diff --git a/configtool/heaterspage.py b/configtool/heaterspage.py
index 181d19c..ce98559 100644
--- a/configtool/heaterspage.py
+++ b/configtool/heaterspage.py
@@ -116,7 +116,7 @@ class HeatersPage(wx.Panel, Page):
     h = self.heaters[self.selection]
 
     dlg = AddHeaterDlg(self, nm, [h[1]] + self.getFreePins(), self.font,
-                       name = h[0], pin = h[1], pwm = h[2])
+                       name = h[0], pin = h[1], invert = h[2], pwm = h[3])
     rc = dlg.ShowModal()
     if rc == wx.ID_OK:
       ht = dlg.getValues()
diff --git a/heater-arm.c b/heater-arm.c
index 690245c..27f0f99 100644
--- a/heater-arm.c
+++ b/heater-arm.c
@@ -1,6 +1,8 @@
 
 /** \file
   \brief Manage heaters, including PID and PWM, ARM specific part.
+
+  For test cases see the intro comment in heater.c.
 */
 
 #if defined TEACUP_C_INCLUDE && defined __ARMEL__
@@ -65,16 +67,18 @@ typedef struct {
     __IO uint32_t* masked_port;
   };
   uint8_t uses_pwm;
+  uint8_t invert;
 } heater_definition_t;
 
 
 #undef DEFINE_HEATER
-#define DEFINE_HEATER(name, pin, pwm) \
+#define DEFINE_HEATER(name, pin, invert, pwm) \
   { \
     { pwm && pin ## _TIMER ? \
       &(pin ## _TIMER->MR[pin ## _MATCH]) : \
       &(pin ## _PORT->MASKED_ACCESS[MASK(pin ## _PIN)]) }, \
-    pwm && pin ## _TIMER \
+    pwm && pin ## _TIMER, \
+    invert ? 1 : 0 \
   },
 static const heater_definition_t heaters[NUM_HEATERS] = {
   #include "config_wrapper.h"
@@ -127,7 +131,7 @@ void heater_init() {
   */
   // Auto-generate pin setup.
   #undef DEFINE_HEATER
-  #define DEFINE_HEATER(name, pin, pwm) \
+  #define DEFINE_HEATER(name, pin, invert, pwm) \
     if (pwm && pin ## _TIMER) {                                             \
       uint32_t freq;                                                        \
                                                                             \
@@ -154,7 +158,7 @@ void heater_init() {
       /* PWM_SCALE - 1, so match = 255 is full off. */                      \
       pin ## _TIMER->MR[3] = PWM_SCALE - 1;       /* Match 3 at 254.     */ \
       pin ## _TIMER->MR[pin ## _MATCH] =          /* Match pin = duty.   */ \
-          PWM_SCALE;                                                        \
+          invert ? 0 : PWM_SCALE;                                           \
       /*pin ## _TIMER->CCR = 0; ( = reset value)     No pin capture.     */ \
       pin ## _TIMER->EMR |= ((1 << pin ## _MATCH) /* Connect to pin.     */ \
           | (0x03 << ((pin ## _MATCH * 2) + 4))); /* Toggle pin on match.*/ \
@@ -164,7 +168,7 @@ void heater_init() {
     }                                                                       \
     else {                                                                  \
       SET_OUTPUT(pin);                                                      \
-      WRITE(pin, 0);                                                        \
+      WRITE(pin, invert ? 1 : 0);                                           \
     }
   #include "config_wrapper.h"
   #undef DEFINE_HEATER
@@ -191,15 +195,22 @@ void heater_set(heater_t index, uint8_t value) {
     heaters_runtime[index].heater_output = value;
 
     if (heaters[index].uses_pwm) {
-      // Remember, we scale, and duty cycle is inverted.
-      *heaters[index].match = PWM_SCALE - ((uint32_t)value * (PWM_SCALE / 255));
+      uint32_t pwm_value;
+
+      // Remember, we scale, and the timer inverts already.
+      pwm_value = (uint32_t)value * (PWM_SCALE / 255);
+      if ( ! heaters[index].invert)
+        pwm_value = PWM_SCALE - pwm_value;
+      *heaters[index].match = pwm_value;
 
       if (DEBUG_PID && (debug_flags & DEBUG_PID))
         sersendf_P(PSTR("PWM %su = %lu\n"), index, *heaters[index].match);
     }
     else {
       *(heaters[index].masked_port) =
-        (value >= HEATER_THRESHOLD) ? 0xFFFF : 0x0000;
+        ((value >= HEATER_THRESHOLD && ! heaters[index].invert) ||
+         (value < HEATER_THRESHOLD && heaters[index].invert)) ?
+        0xFFFF : 0x0000;
     }
 
     if (value)
diff --git a/heater-avr.c b/heater-avr.c
index 663f5ac..993b7cf 100644
--- a/heater-avr.c
+++ b/heater-avr.c
@@ -1,6 +1,8 @@
 
 /** \file
   \brief Manage heaters, including PID and PWM, AVR specific part.
+
+  For test cases see the intro comment in heater.c.
 */
 
 #if defined TEACUP_C_INCLUDE && defined __AVR__
@@ -16,13 +18,15 @@
 typedef struct {
 	volatile uint8_t *heater_port; ///< pointer to port. DDR is inferred from this pointer too
 	uint8_t						heater_pin;  ///< heater pin, not masked. eg for PB3 enter '3' here, or PB3_PIN or similar
+  /// Wether the heater pin signal needs to be inverted.
+  uint8_t          invert;
 	volatile uint8_t *heater_pwm;  ///< pointer to 8-bit PWM register, eg OCR0A (8-bit) or ORC3L (low byte, 16-bit)
 } heater_definition_t;
 
 #undef DEFINE_HEATER
 /// \brief helper macro to fill heater definition struct from config.h
-#define	DEFINE_HEATER(name, pin, pwm) { &(pin ## _WPORT), pin ## _PIN, \
-                                        pwm ? (pin ## _PWM) : NULL},
+#define	DEFINE_HEATER(name, pin, invert, pwm) { \
+  &(pin ## _WPORT), pin ## _PIN, invert ? 1 : 0, pwm ? (pin ## _PWM) : NULL},
 static const heater_definition_t heaters[NUM_HEATERS] =
 {
 	#include	"config_wrapper.h"
@@ -102,10 +106,22 @@ void heater_init() {
 		OCR5B = 0;
 	#endif
 
+  /**
+    - - TODO - - - TODO - - - TODO - - - TODO - -
+
+    This produces a lot of initialisation code for setting up just 2 or 3
+    pins. Can't be optimized out, because heaters[] could have been changed
+    since initialisation.
+
+    A much better strategy for this is the one found in heaters-arm.c: use
+    the config_wrapper.h magic to initialise only what's needed. The needed
+    values are likely already in arduino_xxx.h.
+  */
+
 	// setup pins
 	for (i = 0; i < NUM_HEATERS; i++) {
 		if (heaters[i].heater_pwm) {
-			*heaters[i].heater_pwm = 0;
+			*heaters[i].heater_pwm = heaters[i].invert ? 255 : 0;
 			// this is somewhat ugly too, but switch() won't accept pointers for reasons unknown
 			switch((uint16_t) heaters[i].heater_pwm) {
 				case (uint16_t) &OCR0A:
@@ -180,7 +196,9 @@ void heater_init() {
 
 	// set all heater pins to output
   #undef DEFINE_HEATER
-  #define DEFINE_HEATER(name, pin, pwm) SET_OUTPUT(pin); WRITE(pin, 0);
+  #define DEFINE_HEATER(name, pin, invert, pwm) \
+    SET_OUTPUT(pin);                            \
+    WRITE(pin, invert ? 1 : 0);
   #include "config_wrapper.h"
   #undef DEFINE_HEATER
 }
@@ -198,13 +216,15 @@ void heater_set(heater_t index, uint8_t value) {
 	heaters_runtime[index].heater_output = value;
 
 	if (heaters[index].heater_pwm) {
-		*(heaters[index].heater_pwm) = value;
+    *(heaters[index].heater_pwm) = heaters[index].invert ?
+      (255 - value) : value;
 
 		if (DEBUG_PID && (debug_flags & DEBUG_PID))
 			sersendf_P(PSTR("PWM{%u = %u}\n"), index, *heaters[index].heater_pwm);
 	}
 	else {
-		if (value >= HEATER_THRESHOLD)
+    if ((value >= HEATER_THRESHOLD && ! heaters[index].invert) ||
+        (value < HEATER_THRESHOLD && heaters[index].invert))
 			*(heaters[index].heater_port) |= MASK(heaters[index].heater_pin);
 		else
 			*(heaters[index].heater_port) &= ~MASK(heaters[index].heater_pin);
diff --git a/heater.c b/heater.c
index 43617ef..cf1bfba 100644
--- a/heater.c
+++ b/heater.c
@@ -1,6 +1,24 @@
 
 /** \file
   \brief Manage heaters, including PID and PWM.
+
+  Code for heater_init() and heater_set() is in the platform dependant include
+  file and should pass six test cases when operating the heater via M106, temp
+  sensors disabled:
+
+   - PWM used on PWM-able pin, not inverted.
+   - PWM pin used as on/off pin, not inverted.
+   - Non-PWM-able pin, not inverted.
+   - The three above, but inverted.
+
+  In each test it should pass these tests:
+
+   - Heater full on with M106 S255.
+   - Heater full off with M106 S0.
+   - Heater 10% on with M106 S25 on PWM pins.
+   - Heater full off after reset, power supply turned on by other means.
+   - For testing the inverted cases it's OK to check for behaving the opposite
+     of the M106 command.
 */
 
 #include "heater.h"
diff --git a/heater.h b/heater.h
index 73a41ba..39ffc8c 100644
--- a/heater.h
+++ b/heater.h
@@ -31,7 +31,7 @@
 
 
 #undef DEFINE_HEATER
-#define DEFINE_HEATER(name, pin, pwm) HEATER_ ## name,
+#define DEFINE_HEATER(name, pin, invert, pwm) HEATER_ ## name,
 typedef enum
 {
 	#include "config_wrapper.h"
diff --git a/testcases/config.h.Profiling b/testcases/config.h.Profiling
index 3c78b86..dea3740 100644
--- a/testcases/config.h.Profiling
+++ b/testcases/config.h.Profiling
@@ -447,6 +447,9 @@ DEFINE_TEMP_SENSOR(bed,       TT_THERMISTOR,  AIO0,      THERMISTOR_EXTRUDER)
 * are defined or the order of the definitions differs. The first defined    *
 * device has the index 0 (zero).                                            *
 *                                                                           *
+* Set 'invert' to 0 for normal heaters. Setting it to 1 inverts the pin     *
+* signal for this pin, e.g. for a MOSFET with a driver.                     *
+*                                                                           *
 * Set 'pwm' to ...                                                          *
 *  1  for using PWM on a PWM-able pin and on/off on other pins.             *
 *  0  for using on/off on a PWM-able pin, too.                              *
@@ -460,9 +463,9 @@ DEFINE_TEMP_SENSOR(bed,       TT_THERMISTOR,  AIO0,      THERMISTOR_EXTRUDER)
 	#define DEFINE_HEATER(...)
 #endif
 
-//            name      port   pwm
-DEFINE_HEATER(extruder, DIO4,  1)
-DEFINE_HEATER(bed,      DIO3,  1)
+//            name      pin      invert  pwm
+DEFINE_HEATER(extruder, DIO4,    0,      1)
+DEFINE_HEATER(bed,      DIO3,    0,      1)
 
 /// and now because the c preprocessor isn't as smart as it could be,
 /// uncomment the ones you've listed above and comment the rest.