From eabff30e75429fe1db715c46c123fde678e689e6 Mon Sep 17 00:00:00 2001
From: Scott Lahteine <sourcetree@thinkyhead.com>
Date: Fri, 23 Sep 2016 23:59:16 -0500
Subject: [PATCH] Improve MINIMUM_STEPPER_PULSE

---
 Marlin/Conditionals_post.h |  3 +++
 Marlin/macros.h            |  3 +++
 Marlin/stepper.cpp         | 18 ++++++++++--------
 3 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/Marlin/Conditionals_post.h b/Marlin/Conditionals_post.h
index 89b8afb65..1b5e4188e 100644
--- a/Marlin/Conditionals_post.h
+++ b/Marlin/Conditionals_post.h
@@ -708,4 +708,7 @@
     #define MAX_PROBE_Y (min(Y_MAX_POS, Y_MAX_POS + Y_PROBE_OFFSET_FROM_EXTRUDER))
   #endif
 
+  // Stepper pulse duration, in cycles
+  #define STEP_PULSE_CYCLES ((MINIMUM_STEPPER_PULSE) * CYCLES_PER_MICROSECOND)
+
 #endif // CONDITIONALS_POST_H
diff --git a/Marlin/macros.h b/Marlin/macros.h
index b098597c5..56b5c8bba 100644
--- a/Marlin/macros.h
+++ b/Marlin/macros.h
@@ -36,6 +36,9 @@
   #define CRITICAL_SECTION_END    SREG = _sreg;
 #endif
 
+// Clock speed factor
+#define CYCLES_PER_MICROSECOND (F_CPU / 1000000UL) // 16 or 20
+
 // Remove compiler warning on an unused variable
 #define UNUSED(x) (void) (x)
 
diff --git a/Marlin/stepper.cpp b/Marlin/stepper.cpp
index 9eef09c40..00595e110 100644
--- a/Marlin/stepper.cpp
+++ b/Marlin/stepper.cpp
@@ -460,8 +460,10 @@ void Stepper::isr() {
         _APPLY_STEP(AXIS)(_INVERT_STEP_PIN(AXIS),0); \
       }
 
+    #define CYCLES_EATEN_BY_CODE 240
+
     // If a minimum pulse time was specified get the CPU clock
-    #if MINIMUM_STEPPER_PULSE > 0
+    #if STEP_PULSE_CYCLES > CYCLES_EATEN_BY_CODE
       static uint32_t pulse_start;
       pulse_start = TCNT0;
     #endif
@@ -494,9 +496,8 @@ void Stepper::isr() {
     #endif // !ADVANCE && !LIN_ADVANCE
 
     // For a minimum pulse time wait before stopping pulses
-    #if MINIMUM_STEPPER_PULSE > 0
-      #define CYCLES_EATEN_BY_CODE 10
-      while ((uint32_t)(TCNT0 - pulse_start) < (MINIMUM_STEPPER_PULSE * (F_CPU / 1000000UL)) - CYCLES_EATEN_BY_CODE) { /* nada */ }
+    #if STEP_PULSE_CYCLES > CYCLES_EATEN_BY_CODE
+      while ((uint32_t)(TCNT0 - pulse_start) < STEP_PULSE_CYCLES - CYCLES_EATEN_BY_CODE) { /* nada */ }
     #endif
 
     #if HAS_X_STEP
@@ -688,10 +689,12 @@ void Stepper::isr() {
         E## INDEX ##_STEP_WRITE(INVERT_E_STEP_PIN); \
       }
 
+    #define CYCLES_EATEN_BY_E 60
+
     // Step all E steppers that have steps
     for (uint8_t i = 0; i < step_loops; i++) {
 
-      #if MINIMUM_STEPPER_PULSE > 0
+      #if STEP_PULSE_CYCLES > CYCLES_EATEN_BY_E
         static uint32_t pulse_start;
         pulse_start = TCNT0;
       #endif
@@ -708,9 +711,8 @@ void Stepper::isr() {
       #endif
 
       // For a minimum pulse time wait before stopping pulses
-      #if MINIMUM_STEPPER_PULSE > 0
-        #define CYCLES_EATEN_BY_E 10
-        while ((uint32_t)(TCNT0 - pulse_start) < (MINIMUM_STEPPER_PULSE * (F_CPU / 1000000UL)) - CYCLES_EATEN_BY_E) { /* nada */ }
+      #if STEP_PULSE_CYCLES > CYCLES_EATEN_BY_E
+        while ((uint32_t)(TCNT0 - pulse_start) < STEP_PULSE_CYCLES - CYCLES_EATEN_BY_E) { /* nada */ }
       #endif
 
       STOP_E_PULSE(0);