**Important notes for servo library, servos as hw and rotary encoders.**

====== Library Servo.h ======
''writeMiliseconds()'' - doesnt to anything with values 0-400 to our servo HD-1370A as well as values over 2400. Documentation is silent.

''write()'' - values 0-200 are angle, 200-99999 are position. Very unwise design guys :(

God knows why the interfaces doesnt have three functions
  * ''setAngle()''
  * ''setAbsolutePos() or setStep()''
  * ''writeMagic()'' - yes, here you can do you magic values like 0-200,201+ and so on :)

Your servos -- like mine HP-1370A -- could have rotation range only +/- 60 degrees


====== Rotary encoders ======
There are three (3) ways how to read it
  * digitalRead from pinA and pinB in an infinite loop, keyword: active checking
  * 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 detecting falling edge of pinA

{{:hardware:rotary_encoder_phase.jpg|}}

Once we have it, we check pinB. If pinB is high -> clockwise rotation, pinB is high -> counter-clock.

<code>

    encoder_A = digitalRead(pin_A);    // Read encoder pins
    encoder_B = digitalRead(pin_B);   
    if((!encoder_A) && (encoder_A_prev)){
      // A has gone from high to low 
      if(encoder_B) {
        // B is high so clockwise

      }   
      else {
        // B is low so counter-clockwise      
    
      }   
    }   
</code>

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** not inside 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 :-).