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--- hardware:arduino [2015/03/04 17:35]
admin
+++ hardware:arduino [2015/03/04 17:57]
admin [Rotary encoders]
@@ Line 19: / Line 19: @@
   * direct attach to two (2) interrupt pins, keyword: passive waiting
   * using external IO with counter, keyword: any time baby, any time :)
+Huge note: dont forget 10k pull up resistors.
 ad 1)
-The easiest and most straight forward method. The idea is: we are actively checking (sample rate) 200x per second (200Hz -> 5ms, T = 1/f) falling edge of pinA
+The easiest and most straight forward method. The idea is: we are actively detecting falling edge of pinA
 {{:hardware:rotary_encoder_phase.jpg|}}
@@ Line 28: / Line 30: @@
 <code>
-if ((currentTime - loopTime) > 5)){
     encoder_A = digitalRead(pin_A);    // Read encoder pins
     encoder_B = digitalRead(pin_B);
@@ Line 44: / Line 46: @@
 </code>
-ad 2)
+An example with active checking but only 200x per second.
+Sample rate 200x per second (200Hz -> 5ms, T = 1/f). Useful only if you know exactly which rotary encoder you have! Some starts with 24 pulses per revolution, some have 1024.
+<code>
+#define  TIMESLOT  5
+currentTime = millis();
+if ((currentTime - loopTime) > TIMESLOT)){
+   [....some code....]
+  lastTime=currentTime;
+}
+</code>
+So you dont have to read it like an idiot 1000000x times  per second.
+ad 2) Using interrupts to read a rotary encoder is a perfect job for interrupts because the interrupt service routine (a function) can be short and quick, because it doesn't need to do much.
+<code>
+#define encoderPinA  2
+#define encoderPinB  4
+volatile int encoderPos = 0;
+void setup() {
+ attachInterrupt(0, MyInterrupt, CHANGE);
+}
+MyInterrupt() {
+if (digitalRead(encoderPinA) == digitalRead(encoderPinB)) {
+    encoderPos++;
+  } else {
+    encoderPos--;
+  }
+}
+</code>
+You can print the value outside the MyIntterupt() routine, which should be as fast&small as possible.
+<code>
+void loop() {
+   Serial.println (encoderPos, DEC);
+}
+</code>
+the word //volatile// is **very** important :-).

hardware/arduino.txt · Last modified: 2015/03/04 18:07 by admin