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README.md

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+# PWM Freak
+
+This is very small library for configuring the PWM frequency for AVR based Arduinos. I didnt write it, It is taken from the playground.arduino.cc site and provided in this library for your convenience.
+
+# Why Change the Default Frequency?
+
+If you are controlling a motor, voice coil or any sort of inductive device you 
+are likely hearing a humming sound while using the default PWM frequency. This
+is simply because the switching of the inductive device is within our hearing 
+range. By increasing the frequency to 20Khz (or higher like 31.2Khz) we'll put it
+well above our hearing range...but dont expect the dogs to like it!
+
+# Setting PWM base frequency
+
+Simply add the library using the Arduino library manager and include the PWMFreak.h
+include file.
+
+```
+#include <PWMFreak.h>
+```
+
+Then in your setup function call the function to set the frequency for the given
+pin. The function will figure out what timer is backing that pin and set the PWM
+frequency. Other PWM pins that rely on the same timer will also be affected!
+
+```
+void setup()
+{
+    // change PWM for pin 6 to use divisor value 1
+    setPwmFrequency(6, 1);
+
+}
+```
+
+The resulting frequency is equal to the base frequency divided by
+the given divisor:
+   - Base frequencies:
+      o The base frequency for pins 3, 9, 10, and 11 is 31250 Hz.
+      o The base frequency for pins 5 and 6 is 62500 Hz.
+   - Divisors:
+      o The divisors available on pins 5, 6, 9 and 10 are: 1, 8, 64,
+        256, and 1024.
+      o The divisors available on pins 3 and 11 are: 1, 8, 32, 64,
+        128, 256, and 1024.
+
+PWM frequencies are tied together in pairs of pins. If one in a
+pair is changed, the other is also changed to match:
+* Pins 5 and 6 are paired on timer0
+* Pins 9 and 10 are paired on timer1
+* Pins 3 and 11 are paired on timer2
+
+Note that this function will have side effects on anything else
+that uses timers:
+*   Changes on pins 3, 5, 6, or 11 may cause the delay() and
+    millis() functions to stop working. Other timing-related
+    functions may also be affected.
+*   Changes on pins 9 or 10 will cause the Servo library to function
+    incorrectly.
+
+Thanks to macegr of the Arduino forums for his documentation of the
+PWM frequency divisors. His post can be viewed at:
+   https://forum.arduino.cc/index.php?topic=16612#msg121031
+
+

keywords.txt

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+setPwmFrequency KEYWORD2
+

library.properties

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+name=PWMFreak
+version=0.2
+author=Colin MacKenzie
+maintainer[email protected]
+sentence=Configures the PWM frequency on a pin
+paragraph=A very small library for configuring the PWM frequency for AVR based Arduinos. At least some of this code has been copied from the Internet, see PWMFreak.h for attribution.
+category=Timing
+url=https://github.com/flyingeinstein/PWMFreak
+architectures=avr
+includes=PWMFreak.h

src/PWMFreak.h

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+#include <Arduino.h>
+
+// Taken from:
+// https://playground.arduino.cc/Code/PwmFrequency/
+
+/**
+ * Divides a given PWM pin frequency by a divisor.
+ * 
+ * The resulting frequency is equal to the base frequency divided by
+ * the given divisor:
+ *   - Base frequencies:
+ *      o The base frequency for pins 3, 9, 10, and 11 is 31250 Hz.
+ *      o The base frequency for pins 5 and 6 is 62500 Hz.
+ *   - Divisors:
+ *      o The divisors available on pins 5, 6, 9 and 10 are: 1, 8, 64,
+ *        256, and 1024.
+ *      o The divisors available on pins 3 and 11 are: 1, 8, 32, 64,
+ *        128, 256, and 1024.
+ * 
+ * PWM frequencies are tied together in pairs of pins. If one in a
+ * pair is changed, the other is also changed to match:
+ *   - Pins 5 and 6 are paired on timer0
+ *   - Pins 9 and 10 are paired on timer1
+ *   - Pins 3 and 11 are paired on timer2
+ * 
+ * Note that this function will have side effects on anything else
+ * that uses timers:
+ *   - Changes on pins 3, 5, 6, or 11 may cause the delay() and
+ *     millis() functions to stop working. Other timing-related
+ *     functions may also be affected.
+ *   - Changes on pins 9 or 10 will cause the Servo library to function
+ *     incorrectly.
+ * 
+ * Thanks to macegr of the Arduino forums for his documentation of the
+ * PWM frequency divisors. His post can be viewed at:
+ *   https://forum.arduino.cc/index.php?topic=16612#msg121031
+ */
+
+// sets the PWM frequency for a given pin
+// pulled from the Internet
+void setPwmFrequency(int pin, int divisor) {
+  byte mode;
+  if(pin == 5 || pin == 6 || pin == 9 || pin == 10) {
+    switch(divisor) {
+      case 1: mode = 0x01; break;
+      case 8: mode = 0x02; break;
+      case 64: mode = 0x03; break;
+      case 256: mode = 0x04; break;
+      case 1024: mode = 0x05; break;
+      default: return;
+    }
+    if(pin == 5 || pin == 6) {
+      TCCR0B = TCCR0B & 0b11111000 | mode;
+    } else {
+      TCCR1B = TCCR1B & 0b11111000 | mode;
+    }
+  } else if(pin == 3 || pin == 11) {
+    switch(divisor) {
+      case 1: mode = 0x01; break;
+      case 8: mode = 0x02; break;
+      case 32: mode = 0x03; break;
+      case 64: mode = 0x04; break;
+      case 128: mode = 0x05; break;
+      case 256: mode = 0x06; break;
+      case 1024: mode = 0x07; break;
+      default: return;
+    }
+    TCCR2B = TCCR2B & 0b11111000 | mode;
+  }
+}
+