From 3856d11673a0535e0db15e4a8106012205ba2e5e Mon Sep 17 00:00:00 2001
From: Nico Tonnhofer <wurstnase.reprap@gmail.com>
Date: Wed, 1 Nov 2017 18:28:31 +0100
Subject: [PATCH] home.c: prevent overflow of traveled length while homing. In
 dda.c we have some limitation factors. e.g. the calculation for the
 move_duration. 'distance * 2400' should be everytime below UINT32_MAX. Maybe
 we find later an other limitation factor. So you can modify it now in dda.h.

---
 dda.h  |  3 +++
 home.c | 24 ++++++++++++------------
 2 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/dda.h b/dda.h
index edb67a6..2474d28 100644
--- a/dda.h
+++ b/dda.h
@@ -11,6 +11,9 @@
 	#endif
 #endif
 
+// The distance of any move and a single axis should never go above this limit.
+// Check move_duration and c_limit calculations in dda.c
+#define MAX_DELTA_UM ((int32_t)(UINT32_MAX / 2400L))
 
 // Enum to denote an axis
 enum axis_e { X = 0, Y, Z, E, AXIS_COUNT };
diff --git a/home.c b/home.c
index 3e3e621..25a512b 100644
--- a/home.c
+++ b/home.c
@@ -84,7 +84,7 @@ void home_x_negative() {
 	#if defined X_MIN_PIN
 		TARGET t = startpoint;
 
-    t.axis[X] = -1000000;
+    t.axis[X] = -(MAX_DELTA_UM / 2);
     if (SEARCH_FAST_X > SEARCH_FEEDRATE_X) // Preprocessor can't check this :-/
       t.F = SEARCH_FAST_X;
     else
@@ -93,7 +93,7 @@ void home_x_negative() {
 
     if (SEARCH_FAST_X > SEARCH_FEEDRATE_X) {
 			// back off slowly
-      t.axis[X] = +1000000;
+      t.axis[X] = +(MAX_DELTA_UM / 2);
 			t.F = SEARCH_FEEDRATE_X;
       enqueue_home(&t, 0x01, 0);
     }
@@ -117,7 +117,7 @@ void home_x_positive() {
 	#if defined X_MAX_PIN && defined X_MAX
 		TARGET t = startpoint;
 
-    t.axis[X] = +1000000;
+    t.axis[X] = +(MAX_DELTA_UM / 2);
     if (SEARCH_FAST_X > SEARCH_FEEDRATE_X)
       t.F = SEARCH_FAST_X;
     else
@@ -125,7 +125,7 @@ void home_x_positive() {
     enqueue_home(&t, 0x02, 1);
 
     if (SEARCH_FAST_X > SEARCH_FEEDRATE_X) {
-      t.axis[X] = -1000000;
+      t.axis[X] = -(MAX_DELTA_UM / 2);
 			t.F = SEARCH_FEEDRATE_X;
       enqueue_home(&t, 0x02, 0);
     }
@@ -143,7 +143,7 @@ void home_y_negative() {
 	#if defined Y_MIN_PIN
 		TARGET t = startpoint;
 
-    t.axis[Y] = -1000000;
+    t.axis[Y] = -(MAX_DELTA_UM / 2);
     if (SEARCH_FAST_Y > SEARCH_FEEDRATE_Y)
       t.F = SEARCH_FAST_Y;
     else
@@ -151,7 +151,7 @@ void home_y_negative() {
     enqueue_home(&t, 0x04, 1);
 
     if (SEARCH_FAST_Y > SEARCH_FEEDRATE_Y) {
-      t.axis[Y] = +1000000;
+      t.axis[Y] = +(MAX_DELTA_UM / 2);
 			t.F = SEARCH_FEEDRATE_Y;
       enqueue_home(&t, 0x04, 0);
     }
@@ -175,7 +175,7 @@ void home_y_positive() {
 	#if defined Y_MAX_PIN && defined Y_MAX
 		TARGET t = startpoint;
 
-    t.axis[Y] = +1000000;
+    t.axis[Y] = +(MAX_DELTA_UM / 2);
     if (SEARCH_FAST_Y > SEARCH_FEEDRATE_Y)
       t.F = SEARCH_FAST_Y;
     else
@@ -183,7 +183,7 @@ void home_y_positive() {
     enqueue_home(&t, 0x08, 1);
 
     if (SEARCH_FAST_Y > SEARCH_FEEDRATE_Y) {
-      t.axis[Y] = -1000000;
+      t.axis[Y] = -(MAX_DELTA_UM / 2);
 			t.F = SEARCH_FEEDRATE_Y;
       enqueue_home(&t, 0x08, 0);
     }
@@ -201,7 +201,7 @@ void home_z_negative() {
 	#if defined Z_MIN_PIN
 		TARGET t = startpoint;
 
-    t.axis[Z] = -1000000;
+    t.axis[Z] = -(MAX_DELTA_UM / 2);
     if (SEARCH_FAST_Z > SEARCH_FEEDRATE_Z)
       t.F = SEARCH_FAST_Z;
     else
@@ -209,7 +209,7 @@ void home_z_negative() {
     enqueue_home(&t, 0x10, 1);
 
     if (SEARCH_FAST_Z > SEARCH_FEEDRATE_Z) {
-      t.axis[Z] = +1000000;
+      t.axis[Z] = +(MAX_DELTA_UM / 2);
 			t.F = SEARCH_FEEDRATE_Z;
       enqueue_home(&t, 0x10, 0);
     }
@@ -233,7 +233,7 @@ void home_z_positive() {
 	#if defined Z_MAX_PIN && defined Z_MAX
 		TARGET t = startpoint;
 
-    t.axis[Z] = +1000000;
+    t.axis[Z] = +(MAX_DELTA_UM / 2);
     if (SEARCH_FAST_Z > SEARCH_FEEDRATE_Z)
       t.F = SEARCH_FAST_Z;
     else
@@ -241,7 +241,7 @@ void home_z_positive() {
     enqueue_home(&t, 0x20, 1);
 
     if (SEARCH_FAST_Z > SEARCH_FEEDRATE_Z) {
-      t.axis[Z] = -1000000;
+      t.axis[Z] = -(MAX_DELTA_UM / 2);
 			t.F = SEARCH_FEEDRATE_Z;
       enqueue_home(&t, 0x20, 0);
     }