 #define LED_DEBUG 13
 #define PIN_TX 7
 
-#define PIN_LDR_UP    0 // PC0
-#define PIN_LDR_DOWN  1 // PC1
 #define PIN_LDR_LEFT  2 // PC2
 #define PIN_LDR_RIGHT 3 // PC3
-#define THRESHOLD_LDR_VIRT 50
 #define THRESHOLD_LDR_HORZ 50
 #define MOVE_INTERVAL_MILLIS 60
 
 #define SERVO_INCREMENT 5 // How much to move each loop
 #define SERVO_PIN_HORZ 8 // PB1
-#define SERVO_PIN_VIRT 9 // PB0
 #define SERVO_HORZ_MAX 2800
 #define SERVO_HORZ_MIN 700
-#define SERVO_VIRT_MAX 1900
-#define SERVO_VIRT_MIN 1200
+
 
 #define I2C_SLAVE_ADDR 100
 

      Serial.print("-");
      Serial.println(servo_horz_pos); 
      
      // move a degree each loop until target is reached.
      //servo_horz.attach(SERVO_PIN_HORZ);
      servo_horz.writeMicroseconds(servo_horz_pos);
      
    }
    
}

int tkr_diff_virt()
{
    int up = analogRead(PIN_LDR_UP);
    int down = analogRead(PIN_LDR_DOWN);

    /*
    Serial.print(up); 
    Serial.print(":");
    Serial.print(down); 
    Serial.print(":");
    */
    
    int diff = up - down;
    if (abs(diff) > THRESHOLD_LDR_VIRT) {
      return diff;
    }
    
    return 0;
}

int tkr_diff_horz()

byte msgId = 0;


Servo servo_horz;

// Store the current servo positions. 
int servo_horz_pos = 1700;

void setup()
