Linear advance with I2S streaming

Marlin/Configuration_adv.h

@@ -2042,6 +2042,7 @@
   //#define LA_DEBUG            // If enabled, this will generate debug information output over USB.
   //#define EXPERIMENTAL_SCURVE // Enable this option to permit S-Curve Acceleration
   //#define ALLOW_LOW_EJERK     // Allow a DEFAULT_EJERK value of <10. Recommended for direct drive hotends.
+  //#define EXPERIMENTAL_I2S_LA // Enable this option to permit I2S_STEPPER_STREAM. LA performance degrades as the LA step rate increases above about 20kHz.
 #endif
 
 // @section leveling

Marlin/src/HAL/ESP32/i2s.cpp

@@ -139,21 +139,44 @@ static void IRAM_ATTR i2s_intr_handler_default(void *arg) {
 }
 
 void stepperTask(void *parameter) {
-  uint32_t remaining = 0;
+  uint32_t nextMainISR = 0;
+  #if ENABLED(LIN_ADVANCE)
+    uint32_t nextAdvanceISR = Stepper::LA_ADV_NEVER;
+  #endif
 
   while (1) {
     xQueueReceive(dma.queue, &dma.current, portMAX_DELAY);
     dma.rw_pos = 0;
 
     while (dma.rw_pos < DMA_SAMPLE_COUNT) {
       // Fill with the port data post pulse_phase until the next step
-      if (remaining) {
+      if (nextMainISR && TERN1(LIN_ADVANCE, nextAdvanceISR))
         i2s_push_sample();
-        remaining--;
-      }
-      else {
+
+      // i2s_push_sample() is also called from Stepper::pulse_phase_isr() and Stepper::advance_isr()
+      // in a rare case where both are called, we need to double decrement the counters
+      const uint8_t push_count = !nextMainISR && TERN0(LIN_ADVANCE, !nextAdvanceISR) ? 2 : 1;
+
+      #if ENABLED(LIN_ADVANCE)
+        if (!nextAdvanceISR) {
+          Stepper::advance_isr();
+          nextAdvanceISR = Stepper::la_interval;
+        }
+        else if (nextAdvanceISR == Stepper::LA_ADV_NEVER)
+          nextAdvanceISR = Stepper::la_interval;
+      #endif
+
+      if (!nextMainISR) {
         Stepper::pulse_phase_isr();
-        remaining = Stepper::block_phase_isr();
+        nextMainISR = Stepper::block_phase_isr();
+      }
+
+      LOOP_L_N(i, push_count) {
+        nextMainISR--;
+        #if ENABLED(LIN_ADVANCE)
+          if (nextAdvanceISR != Stepper::LA_ADV_NEVER)
+            nextAdvanceISR--;
+        #endif
       }
     }
   }

Marlin/src/HAL/ESP32/inc/SanityCheck.h

@@ -49,6 +49,6 @@
   #error "PULLDOWN pin mode is not available on ESP32 boards."
 #endif
 
-#if BOTH(I2S_STEPPER_STREAM, LIN_ADVANCE)
+#if BOTH(I2S_STEPPER_STREAM, LIN_ADVANCE) && DISABLED(EXPERIMENTAL_I2S_LA)
   #error "I2S stream is currently incompatible with LIN_ADVANCE."
 #endif

Marlin/src/module/stepper.cpp

@@ -133,6 +133,10 @@ Stepper stepper; // Singleton
   #include "../lcd/extui/ui_api.h"
 #endif
 
+#if ENABLED(I2S_STEPPER_STREAM)
+  #include "../HAL/ESP32/i2s.h"
+#endif
+
 // public:
 
 #if EITHER(HAS_EXTRA_ENDSTOPS, Z_STEPPER_AUTO_ALIGN)
@@ -2468,7 +2472,8 @@ uint32_t Stepper::block_phase_isr() {
     // the acceleration and speed values calculated in block_phase_isr().
     // This helps keep LA in sync with, for example, S_CURVE_ACCELERATION.
     la_delta_error += la_dividend;
-    if (la_delta_error >= 0) {
+    const bool step_needed = la_delta_error >= 0;
+    if (step_needed) {
       count_position.e += count_direction.e;
       la_advance_steps += count_direction.e;
       la_delta_error -= advance_divisor;
@@ -2480,6 +2485,8 @@ uint32_t Stepper::block_phase_isr() {
         E_STEP_WRITE(stepper_extruder, !INVERT_E_STEP_PIN);
       #endif
 
+      TERN_(I2S_STEPPER_STREAM, i2s_push_sample());
+
       // Enforce a minimum duration for STEP pulse ON
       #if ISR_PULSE_CONTROL
         USING_TIMED_PULSE();

Marlin/src/module/stepper.h

@@ -318,6 +318,7 @@ constexpr ena_mask_t enable_overlap[] = {
 class Stepper {
   friend class KinematicSystem;
   friend class DeltaKinematicSystem;
+  friend void stepperTask(void *);
 
   public: