From 50a09824fd8b3d33d62940b6836db350ea8670d5 Mon Sep 17 00:00:00 2001
From: Yuri D'Elia <wavexx@thregr.org>
Date: Tue, 23 Jun 2020 15:20:46 +0200
Subject: [PATCH] Avoid scheduling useless eISR ticks

When switching to a new trapezoid step with the right pressure, cancel
any pending eISR right away.

Similarly do not schedule another eISR if the pressure will be reached
by the end of the eISR.

This was done in the past to preserve the current LA_phase. This is not
needed anymore, since it will be reset at each trapezoid step when LA
is re-initialized.
---
 Firmware/stepper.cpp | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/Firmware/stepper.cpp b/Firmware/stepper.cpp
index b1c3d286..0c7ecae5 100644
--- a/Firmware/stepper.cpp
+++ b/Firmware/stepper.cpp
@@ -864,9 +864,11 @@ FORCE_INLINE void isr() {
     // avoid multiple instances or function calls to advance_spread
     if (la_state & ADV_INIT) {
         LA_phase = -1;
+
         if (current_adv_steps == target_adv_steps) {
-            // nothing to be done in this phase
+            // nothing to be done in this phase, cancel any pending eisr
             la_state = 0;
+            nextAdvanceISR = ADV_NEVER;
         }
         else {
             eISR_Err = current_block->advance_rate / 4;
@@ -933,20 +935,21 @@ FORCE_INLINE void advance_isr() {
             current_adv_steps -= e_step_loops;
         else
             current_adv_steps = 0;
-        nextAdvanceISR = eISR_Rate;
     }
     else if (current_adv_steps < target_adv_steps) {
         // compression
         e_steps += e_step_loops;
         if (e_steps) WRITE_NC(E0_DIR_PIN, e_steps < 0? INVERT_E0_DIR: !INVERT_E0_DIR);
         current_adv_steps += e_step_loops;
-        nextAdvanceISR = eISR_Rate;
     }
-    else {
+
+    if (current_adv_steps == target_adv_steps) {
         // advance steps completed
         nextAdvanceISR = ADV_NEVER;
-        LA_phase = -1;
-        e_step_loops = 1;
+    }
+    else {
+        // schedule another tick
+        nextAdvanceISR = eISR_Rate;
     }
 }