From 3da2363ac52b8454b6ee068a74f03e24b91d6a5a Mon Sep 17 00:00:00 2001
From: Markus Hitter <mah@jump-ing.de>
Date: Thu, 5 Dec 2013 23:38:25 +0100
Subject: [PATCH] DDA: remember the fast axis micrometers and save their
 reconstruction.

No surprise, this saves a whopping 600 bytes.
---
 dda.c           | 34 +++++++++++++---------------------
 dda.h           |  4 ++--
 dda_lookahead.c | 35 +++--------------------------------
 3 files changed, 18 insertions(+), 55 deletions(-)

diff --git a/dda.c b/dda.c
index 8bc953e..fa66d21 100644
--- a/dda.c
+++ b/dda.c
@@ -186,12 +186,19 @@ void dda_create(DDA *dda, TARGET *target) {
                target->Z - startpoint.Z, target->E - startpoint.E);
 
 	dda->total_steps = dda->x_delta;
-	if (dda->y_delta > dda->total_steps)
+  dda->fast_um = x_delta_um;
+  if (dda->y_delta > dda->total_steps) {
 		dda->total_steps = dda->y_delta;
-	if (dda->z_delta > dda->total_steps)
+    dda->fast_um = y_delta_um;
+  }
+  if (dda->z_delta > dda->total_steps) {
 		dda->total_steps = dda->z_delta;
-	if (dda->e_delta > dda->total_steps)
+    dda->fast_um = z_delta_um;
+  }
+  if (dda->e_delta > dda->total_steps) {
 		dda->total_steps = dda->e_delta;
+    dda->fast_um = e_delta_um;
+  }
 
 	if (DEBUG_DDA && (debug_flags & DEBUG_DDA))
     sersendf_P(PSTR(" [ts:%lu"), dda->total_steps);
@@ -347,24 +354,9 @@ void dda_create(DDA *dda, TARGET *target) {
       if (dda->endpoint.F > 65535)
         dda->endpoint.F = 65535;
 
-      // Note: this is inaccurate:
-      // - ACCELERATE_RAMP_LEN() uses STEPS_PER_M_X, so axes not matching
-      //   this get too much or not enough rampup steps.
-      uint32_t fast_um;
-      
-      if (dda->total_steps == dda->x_delta)
-        fast_um = x_delta_um;
-      else if (dda->total_steps == dda->y_delta)
-        fast_um = y_delta_um;
-      else if (dda->total_steps == dda->z_delta)
-        fast_um = z_delta_um;
-      else if (dda->total_steps == dda->e_delta)
-        fast_um = e_delta_um;
-      else {
-        fast_um = 0;
-        sersendf_P(PSTR("WTF? No prev fast axis found\n"));
-      }
-      dda->rampup_steps = ACCELERATE_RAMP_LEN(muldiv(fast_um, dda->endpoint.F, distance));
+      // Acceleration ramps are based on the fast axis, not the combined speed.
+      dda->rampup_steps =
+        ACCELERATE_RAMP_LEN(muldiv(dda->fast_um, dda->endpoint.F, distance));
 
       if (dda->rampup_steps > dda->total_steps / 2)
         dda->rampup_steps = dda->total_steps / 2;
diff --git a/dda.h b/dda.h
index ad65146..cc35eb7 100644
--- a/dda.h
+++ b/dda.h
@@ -126,8 +126,8 @@ typedef struct {
 	uint32_t					z_delta; ///< number of steps on Z axis
 	uint32_t					e_delta; ///< number of steps on E axis
 
-	/// total number of steps: set to \f$\max(\Delta x, \Delta y, \Delta z, \Delta e)\f$
-	uint32_t					total_steps;
+  uint32_t          total_steps; ///< steps of the "fast" axis
+  uint32_t          fast_um;     ///< movement length of this fast axis
 
 	uint32_t					c; ///< time until next step, 24.8 fixed point
 
diff --git a/dda_lookahead.c b/dda_lookahead.c
index f3d45b8..3d5a71f 100644
--- a/dda_lookahead.c
+++ b/dda_lookahead.c
@@ -351,38 +351,9 @@ void dda_join_moves(DDA *prev, DDA *current) {
     //
     // All calculations here are done along the fast axis, so recalculate
     // F and crossF to match this, too.
-    uint32_t fast_um;
-
-    // TODO: instead of reconstructing the fast axis distance, it
-    //       could be stored right in dda_create().
-    if (prev->total_steps == prev->x_delta)
-      fast_um = prev->delta_um.X;
-    else if (prev->total_steps == prev->y_delta)
-      fast_um = prev->delta_um.Y;
-    else if (prev->total_steps == prev->z_delta)
-      fast_um = prev->delta_um.Z;
-    else if (prev->total_steps == prev->e_delta)
-      fast_um = prev->delta_um.E;
-    else {
-      fast_um = 0;
-      sersendf_P(PSTR("WTF? No prev fast axis found\n"));
-    }
-    prev_F = muldiv(fast_um, prev_F, prev->distance);
-
-    if (current->total_steps == current->x_delta)
-      fast_um = current->delta_um.X;
-    else if (current->total_steps == current->y_delta)
-      fast_um = current->delta_um.Y;
-    else if (current->total_steps == current->z_delta)
-      fast_um = current->delta_um.Z;
-    else if (current->total_steps == current->e_delta)
-      fast_um = current->delta_um.E;
-    else {
-      fast_um = 0;
-      sersendf_P(PSTR("WTF? No current fast axis found\n"));
-    }
-    crossF = muldiv(fast_um, crossF, current->distance);
-    this_F = muldiv(fast_um, current->endpoint.F, current->distance);
+    prev_F = muldiv(prev->fast_um, prev_F, prev->distance);
+    this_F = muldiv(current->fast_um, current->endpoint.F, current->distance);
+    crossF = muldiv(current->fast_um, crossF, current->distance);
 
     prev_F_in_steps = ACCELERATE_RAMP_LEN(prev_F);
     this_F_in_steps = ACCELERATE_RAMP_LEN(this_F);