Initial split-up of G-code handlers by category

Marlin/src/gcode/feature/snmm/M702.h

@@ -0,0 +1,50 @@
+/**
+ * Marlin 3D Printer Firmware
+ * Copyright (C) 2016 MarlinFirmware [https://github.com/MarlinFirmware/Marlin]
+ *
+ * Based on Sprinter and grbl.
+ * Copyright (C) 2011 Camiel Gubbels / Erik van der Zalm
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+inline void select_multiplexed_stepper(const uint8_t e) {
+  stepper.synchronize();
+  disable_e_steppers();
+  WRITE(E_MUX0_PIN, TEST(e, 0) ? HIGH : LOW);
+  WRITE(E_MUX1_PIN, TEST(e, 1) ? HIGH : LOW);
+  WRITE(E_MUX2_PIN, TEST(e, 2) ? HIGH : LOW);
+  safe_delay(100);
+}
+
+/**
+ * M702: Unload all extruders
+ */
+void gcode_M702() {
+  for (uint8_t s = 0; s < E_STEPPERS; s++) {
+    select_multiplexed_stepper(e);
+    // TODO: standard unload filament function
+    // MK2 firmware behavior:
+    //  - Make sure temperature is high enough
+    //  - Raise Z to at least 15 to make room
+    //  - Extrude 1cm of filament in 1 second
+    //  - Under 230C quickly purge ~12mm, over 230C purge ~10mm
+    //  - Change E max feedrate to 80, eject the filament from the tube. Sync.
+    //  - Restore E max feedrate to 50
+  }
+  // Go back to the last active extruder
+  select_multiplexed_stepper(active_extruder);
+  disable_e_steppers();
+}