Add external closed loop controller support

Marlin/src/gcode/calibrate/M12.cpp

@@ -0,0 +1,36 @@
+/**
+ * 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/>.
+ *
+ */
+#include "../../inc/MarlinConfigPre.h"
+
+#if ENABLED(EXTERNAL_CLOSED_LOOP_CONTROLLER)
+
+#include "../gcode.h"
+#include "../../module/planner.h"
+#include "../../feature/closedloop.h"
+
+void GcodeSuite::M12() {
+  planner.synchronize();
+  if (parser.seenval('S'))
+    set_closedloop(parser.value_int()); // Force a CLC set
+}
+
+#endif

Marlin/src/gcode/gcode.cpp

@@ -292,6 +292,10 @@ void GcodeSuite::process_parsed_command(
         case 5: M5(); break;                                      // M5 - turn spindle/laser off
       #endif
 
+      #if ENABLED(EXTERNAL_CLOSED_LOOP_CONTROLLER)
+        case 12: M12(); break;                                    // M12: Synchronize and optionally force a CLC set
+      #endif
+
       case 17: M17(); break;                                      // M17: Enable all stepper motors
 
       #if ENABLED(SDSUPPORT)

Marlin/src/gcode/gcode.h

@@ -76,6 +76,7 @@
  * M3   - Turn laser/spindle on, set spindle/laser speed/power, set rotation to clockwise
  * M4   - Turn laser/spindle on, set spindle/laser speed/power, set rotation to counter-clockwise
  * M5   - Turn laser/spindle off
+ * M12  - Set up closed loop control system. More features coming soon. (Requires EXTERNAL_CLOSED_LOOP_CONTROLLER)
  * M17  - Enable/Power all stepper motors
  * M18  - Disable all stepper motors; same as M84
  * M20  - List SD card. (Requires SDSUPPORT)
@@ -438,6 +439,10 @@ private:
     static void M5();
   #endif
 
+  #if ENABLED(EXTERNAL_CLOSED_LOOP_CONTROLLER)
+    static void M12();
+  #endif
+
   static void M17();
 
   static void M18_M84();