Rotary Dimmer to LED Control

            
#define PUSH_BUTTON       23
#define ENCODER_CHA_PIN   19
#define ENCODER_CHB_PIN   20
#define LEV_SHIFT         8
#define ENCODER_DEBONCE   4
#define STATE_IDLE       0xFF
#define STATE_SKIP       0xFE
ZUNO_SETUP_ISR_GPTIMER(gpt_handler);
ZUNO_SETUP_CHANNELS(ZUNO_SWITCH_MULTILEVEL(getter, setter));
byte level = 0;
byte last_reported_level = 0;
byte g_state = STATE_IDLE;
byte g_pins  = 0;
byte g_debounce_time = 0;
byte last_push_button_state = HIGH;
byte stored_level = 0;
dword last_level_changed_time = 0;
// Runs every 128 μs
void gpt_handler() {
      byte pins = 0;
      pins = !digitalRead(ENCODER_CHA_PIN);
      if(!digitalRead(ENCODER_CHB_PIN))
        pins |= 2;
      if(g_pins == pins) {
          // Is the state stable?
          g_debounce_time++;
          if(g_debounce_time>ENCODER_DEBONCE) {
              if(g_state == STATE_IDLE) {
                  g_state = pins;
              }
              else if(g_state == STATE_SKIP) {
                   if(pins == 0)
                     g_state = 0;
              }
              else {
                  if((g_state == 0 && pins == 1) ||
                     (g_state == 1 && pins == 3) ||
                     (g_state == 3 && pins == 2) ||
                     (g_state == 2 && pins == 0) ) {
                        if (level < 39) {
                            level++;
                        }
                        else if ((level + LEV_SHIFT) <= 255) {
                            level += LEV_SHIFT;
                        }
                        else if ((level + LEV_SHIFT) > 255){
                            level = 255;  
                        }
                  }
                  else
                  if((g_state == 0 && pins == 2) ||
                     (g_state == 2 && pins == 3) ||
                     (g_state == 3 && pins == 1) ||
                     (g_state == 1 && pins == 0) ) {
                        if (level <= 39 && level !=0) {
                          level--;
                        }
                        else if (level >= LEV_SHIFT) {
                          level -= LEV_SHIFT;
                        }
                        else if (level < 0) {
                          level = 0;
                        }
                  }
                  if(g_state != pins)    
                    g_state = STATE_SKIP;
              }
              g_debounce_time = 0;
          }  
      }
      else {
          g_debounce_time = 0;
      }
      g_pins = pins;
}
void setup() {
    Serial.begin();
    pinMode(PUSH_BUTTON, INPUT_PULLUP);
    pinMode(ENCODER_CHA_PIN, INPUT);
    pinMode(ENCODER_CHB_PIN, INPUT_PULLUP);
    zunoGPTInit(ZUNO_GPT_SCALE1024|ZUNO_GPT_CYCLIC); // 32 MHz/1024 = 31.25 kHz (tick is 32 μs)
    zunoGPTSet(4); // 32 μs * 4 = 128 μs
    zunoGPTEnable(1);
}
void loop() {
    // Do we need to report the level?
    if(last_reported_level != level) {
        if (level > 0) {
          stored_level = level; 
        }
        last_reported_level = level;
        analogWrite(PWM1, level);
        last_level_changed_time = millis();
        Serial.print("Level: ");
        Serial.println(level);
    }
    // Button handler
    byte current_push_button_state = digitalRead(PUSH_BUTTON);
    if (current_push_button_state != last_push_button_state) {
        last_push_button_state = current_push_button_state;
        // if button pressed
        if (last_push_button_state == LOW) {
            // if LED turned ON, turn OFF   
            if (level > 0) {
                analogWrite(PWM1, 0);
                level = 0;  
            }
            // Restore last level
            else {
                analogWrite(PWM1, stored_level);
                level = stored_level;
            }
        }
    }
    // Send report if 2 seconds level not changed
    if (last_level_changed_time && millis() > last_level_changed_time + 2000) {
        last_level_changed_time = 0;
        zunoSendReport(1); 
    }
}
void setter(byte value) {
    if (value > 99) {
      value = 99;
    }
    level = (long)value * 255 / 99;
    analogWrite(PWM1, level);
}
byte getter(void) {
  return last_reported_level * 99 / 255;
}