From ddd89887278c1402992c903b9e5aa7ef3243dcdf Mon Sep 17 00:00:00 2001
From: Phil Hord <hordp@cisco.com>
Date: Wed, 27 Nov 2013 21:49:42 -0500
Subject: [PATCH] dda_create(): store prev_dda locally.

This obviously requires less place on the stack and accordingly a
few CPU cycles less, but more importantly, it lets decide
dda_start() whether a previous movement is to be taken into account
or not.

To make this decision more reliable, add a flag for movements done.
Else it could happen we'd try to join with a movement done long
before.
---
 dda.c       | 10 +++++++++-
 dda.h       |  5 +++--
 dda_queue.c |  5 ++---
 3 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/dda.c b/dda.c
index 6772a4a..a1fed05 100644
--- a/dda.c
+++ b/dda.c
@@ -83,12 +83,16 @@ void dda_new_startpoint(void) {
 
 	This algorithm is probably the main limiting factor to print speed in terms of firmware limitations
 */
-void dda_create(DDA *dda, TARGET *target, DDA *prev_dda) {
+void dda_create(DDA *dda, TARGET *target) {
 	uint32_t	steps, x_delta_um, y_delta_um, z_delta_um, e_delta_um;
 	uint32_t	distance, c_limit, c_limit_calc;
   #ifdef LOOKAHEAD
   // Number the moves to identify them; allowed to overflow.
   static uint8_t idcnt = 0;
+  static DDA* prev_dda = NULL;
+
+  if (prev_dda && prev_dda->done)
+    prev_dda = NULL;
   #endif
 
 	// initialise DDA to a known state
@@ -405,6 +409,9 @@ void dda_create(DDA *dda, TARGET *target, DDA *prev_dda) {
 
 	// next dda starts where we finish
 	memcpy(&startpoint, target, sizeof(TARGET));
+  #ifdef LOOKAHEAD
+    prev_dda = dda;
+  #endif
 }
 
 /*! Start a prepared DDA
@@ -637,6 +644,7 @@ void dda_step(DDA *dda) {
     #endif
       ) {
 		dda->live = 0;
+    dda->done = 1;
     #ifdef LOOKAHEAD
     // If look-ahead was using this move, it could have missed our activation:
     // make sure the ids do not match.
diff --git a/dda.h b/dda.h
index 32cc893..59b84a4 100644
--- a/dda.h
+++ b/dda.h
@@ -103,6 +103,7 @@ typedef struct {
 			// status fields
 			uint8_t						nullmove			:1; ///< bool: no axes move, maybe we wait for temperatures or change speed
 			uint8_t						live					:1; ///< bool: this DDA is running and still has steps to do
+      uint8_t           done          :1; ///< bool: this DDA is done.
 			#ifdef ACCELERATION_REPRAP
 			uint8_t						accel					:1; ///< bool: speed changes during this move, run accel code
 			#endif
@@ -116,7 +117,7 @@ typedef struct {
 			uint8_t						z_direction		:1; ///< direction flag for Z axis
 			uint8_t						e_direction		:1; ///< direction flag for E axis
 		};
-		uint8_t							allflags;	///< used for clearing all flags
+    uint16_t            allflags; ///< used for clearing all flags
 	};
 
 	// distances
@@ -198,7 +199,7 @@ void dda_init(void);
 void dda_new_startpoint(void);
 
 // create a DDA
-void dda_create(DDA *dda, TARGET *target, DDA *prev_dda);
+void dda_create(DDA *dda, TARGET *target);
 
 // start a created DDA (called from timer interrupt)
 void dda_start(DDA *dda)																						__attribute__ ((hot));
diff --git a/dda_queue.c b/dda_queue.c
index 6e3c73b..d433d47 100644
--- a/dda_queue.c
+++ b/dda_queue.c
@@ -84,7 +84,7 @@ void queue_step() {
 		if (current_movebuffer->waitfor_temp) {
 			setTimer(HEATER_WAIT_TIMEOUT);
 			if (temp_achieved()) {
-				current_movebuffer->live = current_movebuffer->waitfor_temp = 0;
+				current_movebuffer->live = current_movebuffer->done = 0;
 				serial_writestr_P(PSTR("Temp achieved\n"));
 			}
 		}
@@ -112,10 +112,9 @@ void enqueue_home(TARGET *t, uint8_t endstop_check, uint8_t endstop_stop_cond) {
 	h &= (MOVEBUFFER_SIZE - 1);
 
 	DDA* new_movebuffer = &(movebuffer[h]);
-  DDA* prev_movebuffer = (queue_empty() != 0) ? NULL : &movebuffer[mb_head];
 
   if (t != NULL) {
-    dda_create(new_movebuffer, t, prev_movebuffer);
+    dda_create(new_movebuffer, t);
 		new_movebuffer->endstop_check = endstop_check;
 		new_movebuffer->endstop_stop_cond = endstop_stop_cond;
 	}