Remove several globals by using a single target pressure

In the current code we initialize the LA state on-demand already at the
right step, which makes keeping track of the tick position no longer
necessary.

Make the advance ISR almost stateless by removing the last vestiges of
the original implementation and introduce a single target pressure. This
will be needed later in order to trigger the LA isr inside the cruising
phase.

Firmware/stepper.cpp

@@ -128,9 +128,7 @@ volatile signed char count_direction[NUM_AXIS] = { 1, 1, 1, 1};
   static uint16_t eISR_Err;
 
   static uint16_t current_adv_steps;
-  static uint16_t final_adv_steps;
-  static uint16_t max_adv_steps;
-  static uint32_t LA_decelerate_after;
+  static uint16_t target_adv_steps;
 
   static int8_t e_steps;
   static uint8_t e_step_loops;
@@ -349,10 +347,8 @@ FORCE_INLINE void stepper_next_block()
 
 #ifdef LIN_ADVANCE
     if (current_block->use_advance_lead) {
-        LA_decelerate_after = current_block->decelerate_after;
-        final_adv_steps = current_block->final_adv_steps;
-        max_adv_steps = current_block->max_adv_steps;
         e_step_loops = current_block->advance_step_loops;
+        target_adv_steps = current_block->max_adv_steps;
     } else {
         e_step_loops = 1;
         current_adv_steps = 0;
@@ -827,11 +823,14 @@ FORCE_INLINE void isr() {
         uint16_t timer = calc_timer(step_rate, step_loops);
         _NEXT_ISR(timer);
         deceleration_time += timer;
+
 #ifdef LIN_ADVANCE
         if (current_block->use_advance_lead) {
             la_state = ADV_DECELERATE;
-            if (step_events_completed.wide <= (unsigned long int)current_block->decelerate_after + step_loops)
+            if (step_events_completed.wide <= (unsigned long int)current_block->decelerate_after + step_loops) {
+                target_adv_steps = current_block->final_adv_steps;
                 la_state |= ADV_INIT;
+            }
         }
 #endif
       }
@@ -898,7 +897,7 @@ FORCE_INLINE void isr() {
 // Timer interrupt for E. e_steps is set in the main routine.
 
 FORCE_INLINE void advance_isr() {
-    if (step_events_completed.wide > LA_decelerate_after && current_adv_steps > final_adv_steps) {
+    if (current_adv_steps > target_adv_steps) {
         // decompression
         e_steps -= e_step_loops;
         if (e_steps) WRITE_NC(E0_DIR_PIN, e_steps < 0? INVERT_E0_DIR: !INVERT_E0_DIR);
@@ -908,7 +907,7 @@ FORCE_INLINE void advance_isr() {
             current_adv_steps = 0;
         nextAdvanceISR = eISR_Rate;
     }
-    else if (step_events_completed.wide < LA_decelerate_after && current_adv_steps < max_adv_steps) {
+    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);
@@ -1233,9 +1232,6 @@ void st_init()
   nextMainISR = 0;
   nextAdvanceISR = ADV_NEVER;
   main_Rate = ADV_NEVER;
-  e_steps = 0;
-  e_step_loops = 1;
-  LA_phase = -1;
   current_adv_steps = 0;
 #endif