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

#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


    pinMode(LED_DEBUG, OUTPUT);     
    pinMode(PIN_TX, OUTPUT); 

    servo_horz.attach(SERVO_PIN_HORZ, SERVO_HORZ_MIN, SERVO_HORZ_MAX);

    servo_horz.writeMicroseconds(servo_horz_pos);
    
    // Join the i2c bus as master
