From ba13ddadd0390befd0d659c879558572e246d049 Mon Sep 17 00:00:00 2001
From: Simen Svale Skogsrud <simen@bengler.no>
Date: Sun, 6 Feb 2011 23:52:12 +0100
Subject: [PATCH] refactoring that improved compartmentalization between
 stepper and stepper_plan modules

---
 stepper.c      | 10 ++++------
 stepper_plan.c | 11 +++++++++++
 stepper_plan.h | 10 +++++++---
 3 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/stepper.c b/stepper.c
index 467fed5..d03c026 100644
--- a/stepper.c
+++ b/stepper.c
@@ -144,9 +144,8 @@ SIGNAL(TIMER1_COMPA_vect)
   // If there is no current block, attempt to pop one from the buffer
   if (current_block == NULL) {
     // Anything in the buffer?
-    if (block_buffer_head != block_buffer_tail) {
-      // Retrieve a new line and get ready to step it
-      current_block = &block_buffer[block_buffer_tail]; 
+    current_block = plan_get_current_block();
+    if (current_block != NULL) {
       trapezoid_generator_reset();
       counter_x = -(current_block->step_event_count >> 1);
       counter_y = counter_x;
@@ -184,8 +183,7 @@ SIGNAL(TIMER1_COMPA_vect)
       // printInteger(current_block->rate_delta);
       // printString(" <-- delta\n\r");
       current_block = NULL;
-      // move the block buffer tail to the next instruction
-      block_buffer_tail = (block_buffer_tail + 1) % BLOCK_BUFFER_SIZE;
+      plan_discard_current_block();
     }
   } else {
     out_bits = 0;
@@ -252,7 +250,7 @@ void st_init()
 // Block until all buffered steps are executed
 void st_synchronize()
 {
-  while(block_buffer_tail != block_buffer_head) { sleep_mode(); }    
+  while(plan_get_current_block()) { sleep_mode(); }    
 }
 
 // Configures the prescaler and ceiling of timer 1 to produce the given rate as accurately as possible.
diff --git a/stepper_plan.c b/stepper_plan.c
index 0d972f9..7d0de45 100644
--- a/stepper_plan.c
+++ b/stepper_plan.c
@@ -351,6 +351,17 @@ int plan_is_acceleration_manager_enabled() {
   return(acceleration_manager_enabled);
 }
 
+inline void plan_discard_current_block() {
+  if (block_buffer_head != block_buffer_tail) {
+    block_buffer_tail = (block_buffer_tail + 1) % BLOCK_BUFFER_SIZE;  
+  }
+}
+
+inline block_t *plan_get_current_block() {
+  if (block_buffer_head == block_buffer_tail) { return(NULL); }
+  return(&block_buffer[block_buffer_tail]);
+}
+
 // Add a new linear movement to the buffer. steps_x, _y and _z is the absolute position in 
 // mm. Microseconds specify how many microseconds the move should take to perform. To aid acceleration
 // calculation the caller must also provide the physical length of the line in millimeters.
diff --git a/stepper_plan.h b/stepper_plan.h
index 0d04c1c..1f71d7e 100644
--- a/stepper_plan.h
+++ b/stepper_plan.h
@@ -56,9 +56,6 @@ typedef struct {
   uint32_t exit_rate;
 } block_t;
       
-extern block_t block_buffer[BLOCK_BUFFER_SIZE]; // A ring buffer for motion instructions
-extern volatile int block_buffer_head;           // Index of the next block to be pushed
-extern volatile int block_buffer_tail;           // Index of the block to process now
 extern int32_t position[3];
 
 // Initialize the motion plan subsystem      
@@ -71,6 +68,13 @@ void plan_init();
 // calculation the caller must also provide the physical length of the line in millimeters.
 void plan_buffer_line(double x, double y, double z, double feed_rate, int invert_feed_rate);
 
+// Call when the current block is no longer needed. Discards the block and makes the memory
+// availible for new blocks.
+inline void plan_discard_current_block();
+
+// Gets the current block. Returns NULL if buffer empty
+inline block_t *plan_get_current_block();
+
 // Enables acceleration-management for upcoming blocks
 void plan_set_acceleration_manager_enabled(int enabled);
 // Is acceleration-management currently enabled?