From c1a6c244b3ae269d64a01eb861b4ce9d6050b292 Mon Sep 17 00:00:00 2001
From: Markus Hitter <mah@jump-ing.de>
Date: Sat, 26 Oct 2013 21:15:41 +0200
Subject: [PATCH] dda.c: re-gain look-ahead compatibility.

We're here! Incredible high step rates as well as smooth
movements due to look-ahead.
---
 dda.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/dda.c b/dda.c
index c6af69e..11e7c01 100644
--- a/dda.c
+++ b/dda.c
@@ -344,11 +344,18 @@ void dda_create(DDA *dda, TARGET *target, DDA *prev_dda) {
 
       #ifdef LOOKAHEAD
         dda_join_moves(prev_dda, dda);
+        dda->n = ACCELERATE_RAMP_LEN(dda->F_start);
+        if (dda->n == 0)
+          dda->c = C0;
+        else
+          dda->c = ((C0 >> 8) * int_inv_sqrt(dda->n)) >> 5;
+        if (dda->c < dda->c_min)
+          dda->c = dda->c_min;
+      #else
+        dda->n = 0;
+        dda->c = C0;
       #endif
 
-      dda->n = 0;
-      dda->c = C0;
-
 		#elif defined ACCELERATION_TEMPORAL
 			// TODO: limit speed of individual axes to MAXIMUM_FEEDRATE
 			// TODO: calculate acceleration/deceleration for each axis
@@ -659,9 +666,6 @@ void dda_step(DDA *dda) {
   movement direction 500 times a second is easily enough for smooth and
   accurate curves!
 */
-#ifdef LOOKAHEAD
-  #error Look-ahead currently not supported. Turn it off or use an earlier commit.
-#endif
 void dda_clock() {
   static volatile uint8_t busy = 0;
   DDA *dda;