diff --git a/main.c b/main.c
index a6f509c..1083d31 100644
--- a/main.c
+++ b/main.c
@@ -41,6 +41,8 @@ int main(void)
   
   st_start(); // start the stepper subsystem
   
+  DDRD |= (1<<3)|(1<<4)|(1<<5);
+  
   for(;;){
     sleep_mode();
     sp_process(); // process the serial protocol
diff --git a/motion_control.c b/motion_control.c
index b9939b4..00fd1f0 100644
--- a/motion_control.c
+++ b/motion_control.c
@@ -90,34 +90,44 @@ void mc_line(double x, double y, double z, float feed_rate, int invert_feed_rate
     maximum_steps;   // The larges absolute step-count of any axis  
   
   // Setup ---------------------------------------------------------------------------------------------------
-
+  PORTD |= (1<<4);
+  PORTD |= (1<<5);
   target[X_AXIS] = round(x*X_STEPS_PER_MM);
   target[Y_AXIS] = round(y*Y_STEPS_PER_MM);
   target[Z_AXIS] = round(z*Z_STEPS_PER_MM); 
+  PORTD ^= (1<<5);
   // Determine direction and travel magnitude for each axis
   for(axis = X_AXIS; axis <= Z_AXIS; axis++) {
   	step_count[axis] = labs(target[axis] - position[axis]);
     direction[axis] = signof(target[axis] - position[axis]);
   }
+  PORTD ^= (1<<5);
   // Find the magnitude of the axis with the longest travel
 	maximum_steps = max(step_count[Z_AXIS], 
 	  max(step_count[X_AXIS], step_count[Y_AXIS]));
+  PORTD ^= (1<<5);
   // Nothing to do?
-	if (maximum_steps == 0) { return; }
+  if (maximum_steps == 0) { PORTD &= ~(1<<4); PORTD |= (1<<5); return; }
+  PORTD ^= (1<<5);
 	// Set up a neat counter for each axis
   for(axis = X_AXIS; axis <= Z_AXIS; axis++) {
     counter[axis] = -maximum_steps/2;
   }
+  PORTD ^= (1<<5);
 	// Set our direction pins 
   set_stepper_directions(direction);
+  PORTD ^= (1<<5);
 
 	// Ask old Phytagoras to estimate how many mm our next move is going to take us
 	double millimeters_of_travel = 
     sqrt(square(X_STEPS_PER_MM*step_count[X_AXIS]) + 
         square(Y_STEPS_PER_MM*step_count[Y_AXIS]) + 
         square(Z_STEPS_PER_MM*step_count[Z_AXIS]));
+      PORTD ^= (1<<5);
   // And set the step pace
   compute_and_set_step_pace(feed_rate, millimeters_of_travel, maximum_steps, invert_feed_rate);
+  PORTD &= ~(1<<5);
+  PORTD &= ~(1<<4);
   
   // Execution -----------------------------------------------------------------------------------------------
 
diff --git a/serial_protocol.c b/serial_protocol.c
index 5a3739f..f1cf29b 100644
--- a/serial_protocol.c
+++ b/serial_protocol.c
@@ -77,7 +77,7 @@ void sp_process()
   char c;
   while((c = serialRead()) != -1) 
   {
-    if((c < 32)) {  // Line is complete. Then execute!
+    if((c == '\n')) {  // Line is complete. Then execute!
       line[line_counter] = 0;
       // printString("->");
       // printString(line);
@@ -85,7 +85,7 @@ void sp_process()
       gc_execute_line(line);
       line_counter = 0;
       prompt();
-    } else if (c == ' ' || c == '\t') { // Throw away whitepace
+    } else if (c <= ' ') { // Throw away whitepace and control characters
     } else if (c >= 'a' && c <= 'z') { // Upcase lowercase
       line[line_counter++] = c-'a'+'A';
     } else {
diff --git a/stepper.c b/stepper.c
index 7b8da0a..ff4704e 100644
--- a/stepper.c
+++ b/stepper.c
@@ -53,6 +53,7 @@ void config_pace_timer(uint32_t microseconds);
 SIGNAL(SIG_OUTPUT_COMPARE1A)
 {
   if (step_buffer_head != step_buffer_tail) {
+    PORTD &= ~(1<<3);
     uint8_t popped = step_buffer[step_buffer_tail]; 
     if(popped == PACE_CHANGE_MARKER) {
       // This is not a step-instruction, but a pace-change-marker: change pace
@@ -69,6 +70,8 @@ SIGNAL(SIG_OUTPUT_COMPARE1A)
     }
     // move the step buffer tail to the next instruction
     step_buffer_tail = (step_buffer_tail + 1) % STEP_BUFFER_SIZE;
+  } else {
+    PORTD |= (1<<3);    
   }
 }