Added option to increase the FAN PWM frequency.

Marlin/Configuration.h

 //User specified version info of THIS file to display in [Pronterface, etc] terminal window during startup.
 //Implementation of an idea by Prof Braino to inform user that any changes made
 //to THIS file by the user have been successfully uploaded into firmware.
-#define STRING_VERSION_CONFIG_H "2012-02-25" //Personal revision number for changes to THIS file.
+#define STRING_VERSION_CONFIG_H "2012-05-02" //Personal revision number for changes to THIS file.
 #define STRING_CONFIG_H_AUTHOR "erik" //Who made the changes.
 
 // This determines the communication speed of the printer
   #endif
 #endif
 
+// Increase the FAN pwm frequency. Removes the PWM noise but increases heating in the FET/Arduino
+#define FAST_PWM_FAN
+
 // M240  Triggers a camera by emulating a Canon RC-1 Remote
 // Data from: http://www.doc-diy.net/photo/rc-1_hacked/
 // #define PHOTOGRAPH_PIN     23

Marlin/Marlin.h

 void enquecommand(const char *cmd); //put an ascii command at the end of the current buffer.
 void prepare_arc_move(char isclockwise);
 
+#ifdef FAST_PWM_FAN
+void setPwmFrequency(uint8_t pin, int val);
+#endif
+
 #ifndef CRITICAL_SECTION_START
   #define CRITICAL_SECTION_START  unsigned char _sreg = SREG; cli();
   #define CRITICAL_SECTION_END    SREG = _sreg;

Marlin/Marlin.pde

 #include "watchdog.h"
 #include "EEPROMwrite.h"
 #include "language.h"
+#include "pins_arduino.h"
 
 #define VERSION_STRING  "1.0.0 RC2"
 
 
 bool IsStopped() { return Stopped; };
 
+#ifdef FAST_PWM_FAN
+void setPwmFrequency(uint8_t pin, int val)
+{
+  val &= 0x07;
+  switch(digitalPinToTimer(pin))
+  {
+ 
+    #if defined(TCCR0A)
+    case TIMER0A:
+    case TIMER0B:
+         TCCR0B &= ~(CS00 | CS01 | CS02);
+         TCCR0B |= val;
+         break;
+    #endif
+
+    #if defined(TCCR1A)
+    case TIMER1A:
+    case TIMER1B:
+         TCCR1B &= ~(CS10 | CS11 | CS12);
+         TCCR1B |= val;
+         break;
+    #endif
+
+    #if defined(TCCR2)
+    case TIMER2:
+    case TIMER2:
+         TCCR2 &= ~(CS10 | CS11 | CS12);
+         TCCR2 |= val;
+         break;
+    #endif
+
+    #if defined(TCCR2A)
+    case TIMER2A:
+    case TIMER2B:
+         TCCR2B &= ~(CS20 | CS21 | CS22);
+         TCCR2B |= val;
+         break;
+    #endif
+
+    #if defined(TCCR3A)
+    case TIMER3A:
+    case TIMER3B:
+    case TIMER3C:
+         TCCR3B &= ~(CS30 | CS31 | CS32);
+         TCCR3B |= val;
+         break;
+    #endif
+
+    #if defined(TCCR4A) 
+    case TIMER4A:
+    case TIMER4B:
+    case TIMER4C:
+         TCCR4B &= ~(CS40 | CS41 | CS42);
+         TCCR4B |= val;
+         break;
+   #endif
+
+    #if defined(TCCR5A) 
+    case TIMER5A:
+    case TIMER5B:
+    case TIMER5C:
+         TCCR5B &= ~(CS50 | CS51 | CS52);
+         TCCR5B |= val;
+         break;
+   #endif
+
+  }
+}
+#endif
+
 

Marlin/temperature.cpp

   #endif  
   #if (FAN_PIN > -1) 
     SET_OUTPUT(FAN_PIN);
+    #ifdef FAST_PWM_FAN
+    setPwmFrequency(FAN_PIN, 1); // No prescaling. Pwm frequency = F_CPU/256/8
+    #endif
   #endif  
 
   #ifdef HEATER_0_USES_MAX6675