Implement automatic extruder/cold-end fan control based on temperature

This change allows fan outputs to automatically turn on/off when the
associated nozzle temperature of an extruder is above/below a threshold
temperature.
Multiple extruders can be assigned to the same pin in which case the fan
will turn on when any selected extruder is above the threshold.
It also makes the M42 command compatible with the M106/M107 command.
The majority of the logic in this change will be evaluated by the
compiler at build time (i.e, low code space requirements).

Marlin/Configuration_adv.h

@@ -71,6 +71,16 @@
 // before setting a PWM value. (Does not work with software PWM for fan on Sanguinololu)
 //#define FAN_KICKSTART_TIME 100
 
+// Configure fan pin outputs to automatically turn on/off when the associated
+// extruder temperature is above/below EXTRUDER_AUTO_FAN_TEMPERATURE.
+// Multiple extruders can be assigned to the same pin in which case 
+// the fan will turn on when any selected extruder is above the threshold.
+#define EXTRUDER_0_AUTO_FAN_PIN   -1
+#define EXTRUDER_1_AUTO_FAN_PIN   -1
+#define EXTRUDER_2_AUTO_FAN_PIN   -1
+#define EXTRUDER_AUTO_FAN_TEMPERATURE 50
+#define EXTRUDER_AUTO_FAN_SPEED   255  // == full speed
+
 //===========================================================================
 //=============================Mechanical Settings===========================
 //===========================================================================

Marlin/Marlin_main.cpp

@@ -982,6 +982,10 @@ void process_commands()
             break;
           }
         }
+      #if FAN_PIN > -1
+        if (pin_number == FAN_PIN)
+          fanSpeed = pin_status;
+      #endif
         if (pin_number > -1)
         {
           pinMode(pin_number, OUTPUT);

Marlin/temperature.cpp

@@ -99,8 +99,9 @@ static volatile bool temp_meas_ready = false;
 #ifdef FAN_SOFT_PWM
   static unsigned char soft_pwm_fan;
 #endif
-
-
+#if EXTRUDER_0_AUTO_FAN_PIN > -1 || EXTRUDER_1_AUTO_FAN_PIN > -1 || EXTRUDER_2_AUTO_FAN_PIN > -1
+  static uint8_t extruderAutoFanState = 0; // extruder auto fan state stored as bitmap
+#endif  
   
 #if EXTRUDERS > 3
 # error Unsupported number of extruders
@@ -399,6 +400,55 @@ void manage_heater()
 
   } // End extruder for loop
   
+  #if EXTRUDER_0_AUTO_FAN_PIN > -1
+    // check the extruder 0 setting (and any ganged auto fan outputs)
+    bool newFanState = (EXTRUDER_0_AUTO_FAN_PIN > -1 && 
+        (current_temperature[0] > EXTRUDER_AUTO_FAN_TEMPERATURE || 
+            (EXTRUDER_0_AUTO_FAN_PIN == EXTRUDER_1_AUTO_FAN_PIN && current_temperature[1] > EXTRUDER_AUTO_FAN_TEMPERATURE) || 
+            (EXTRUDER_0_AUTO_FAN_PIN == EXTRUDER_2_AUTO_FAN_PIN && current_temperature[2] > EXTRUDER_AUTO_FAN_TEMPERATURE)));
+    if ((extruderAutoFanState & 1) != newFanState) // store state in first bit
+    {
+        int newFanSpeed = (newFanState ? EXTRUDER_AUTO_FAN_SPEED : 0);
+        if (EXTRUDER_0_AUTO_FAN_PIN == FAN_PIN) 
+            fanSpeed = newFanSpeed;
+        pinMode(EXTRUDER_0_AUTO_FAN_PIN, OUTPUT);
+        digitalWrite(EXTRUDER_0_AUTO_FAN_PIN, newFanSpeed);
+        analogWrite(EXTRUDER_0_AUTO_FAN_PIN, newFanSpeed);
+        extruderAutoFanState = newFanState | (extruderAutoFanState & ~1);
+    }
+  #endif //EXTRUDER_0_AUTO_FAN_PIN > -1
+  #if EXTRUDER_1_AUTO_FAN_PIN > -1
+    // check the extruder 1 setting (except when extruder 1 is the same as 0)
+    newFanState = (EXTRUDER_1_AUTO_FAN_PIN > -1 && EXTRUDER_1_AUTO_FAN_PIN != EXTRUDER_0_AUTO_FAN_PIN &&
+        (current_temperature[1] > EXTRUDER_AUTO_FAN_TEMPERATURE ||
+            (EXTRUDER_1_AUTO_FAN_PIN == EXTRUDER_2_AUTO_FAN_PIN && current_temperature[2] > EXTRUDER_AUTO_FAN_TEMPERATURE)));
+    if ((extruderAutoFanState & 2) != (newFanState<<1)) // use second bit
+    {
+        int newFanSpeed = (newFanState ? EXTRUDER_AUTO_FAN_SPEED : 0);
+        if (EXTRUDER_1_AUTO_FAN_PIN == FAN_PIN) 
+            fanSpeed = newFanSpeed;
+        pinMode(EXTRUDER_1_AUTO_FAN_PIN, OUTPUT);
+        digitalWrite(EXTRUDER_1_AUTO_FAN_PIN, newFanSpeed);
+        analogWrite(EXTRUDER_1_AUTO_FAN_PIN, newFanSpeed);
+        extruderAutoFanState = (newFanState<<1) | (extruderAutoFanState & ~2);
+    }
+  #endif //EXTRUDER_1_AUTO_FAN_PIN > -1
+  #if EXTRUDER_2_AUTO_FAN_PIN > -1
+    // check the extruder 2 setting (except when extruder 2 is the same as 1 or 0)
+    newFanState = (EXTRUDER_2_AUTO_FAN_PIN > -1 && 
+            EXTRUDER_2_AUTO_FAN_PIN != EXTRUDER_0_AUTO_FAN_PIN && EXTRUDER_2_AUTO_FAN_PIN != EXTRUDER_1_AUTO_FAN_PIN &&
+        current_temperature[2] > EXTRUDER_AUTO_FAN_TEMPERATURE);
+    if ((extruderAutoFanState & 4) != (newFanState<<2)) // use third bit
+    {
+        int newFanSpeed = (newFanState ? EXTRUDER_AUTO_FAN_SPEED : 0);
+        if (EXTRUDER_2_AUTO_FAN_PIN == FAN_PIN) 
+            fanSpeed = newFanSpeed;
+        pinMode(EXTRUDER_2_AUTO_FAN_PIN, OUTPUT);
+        digitalWrite(EXTRUDER_2_AUTO_FAN_PIN, newFanSpeed);
+        analogWrite(EXTRUDER_2_AUTO_FAN_PIN, newFanSpeed);
+        extruderAutoFanState = (newFanState<<2) | (extruderAutoFanState & ~4);
+    }
+  #endif //EXTRUDER_2_AUTO_FAN_PIN > -1
 
   #ifndef PIDTEMPBED
   if(millis() - previous_millis_bed_heater < BED_CHECK_INTERVAL)

README.md

@@ -1,8 +1,11 @@
-WARNING: 
---------
-THIS IS RELEASE CANDIDATE 2 FOR MARLIN 1.0.0
+==========================
+Marlin 3D Printer Firmware
+==========================
 
-The configuration is now split in two files
+Notes: 
+-----
+
+The configuration is now split in two files:
   Configuration.h for the normal settings
   Configuration_adv.h for the advanced settings
 
@@ -46,6 +49,7 @@ Features:
 *   PID tuning
 *   CoreXY kinematics (www.corexy.com/theory.html)
 *   Configurable serial port to support connection of wireless adaptors.
+*   Automatic operation of extruder/cold-end cooling fans based on nozzle temperature
 
 The default baudrate is 250000. This baudrate has less jitter and hence errors than the usual 115200 baud, but is less supported by drivers and host-environments.