Automatically save PID settings to EEPROM after M301, M304, and M303 U1

README.md

@@ -19,6 +19,8 @@ a few goodies:
 * **OctoPrint screen**: Adds support for `M73` (print progress) and `M117`
   (LCD messages).
 * **Sound**: Adds support for `M300` (play a sound).
+* **PID tuning**: Automatically writes PID settings to EEPROM after `M303 U1` (autotune),
+  `M301` (set hotend PID), and `M304` (set bed PID).
 
 All settings are automatically saved to EEPROM and loaded on boot.
 
@@ -137,6 +139,25 @@ mesh bed leveling. A skew factor of e.g. 0.01 equates to
 `0.01 * 180mm = 1.8mm` of movement at the far end of the bed,
 so your usable print area will be reduced accordingly.
 
+### Configuring PID Parameters
+
+The stock firmware allows you to run an `M303` PID autotune, but the new
+settings are lost on reset. In Llama, PID settings are *automatically* written
+to EEPROM after any command that updates Marlin's PID values, which could be
+an `M301` (set hotend PID), `M304` (set bed PID), or an `M303 U1` (autotune and
+use the PID result). These values will then be restored on reset, too. You do not
+need to use `M500`.
+
+If you need to restore the default PID values, they can be reset by running
+the following commands:
+
+* Hotend: `M301 P7.00 I0.50 D45.00`
+* Bed: `M304 P120.00 I1.50 D600.0`
+
+Note that if you run `M303` (autotune) without the `U1` parameter, Marlin
+will just print out the suggested PID values without changing the settings,
+and they won't get written to EEPROM.
+
 ---
 
 ### Print Progress

src/common/marlin_server.cpp

@@ -414,6 +414,20 @@ void marlin_server_settings_save(void) {
 #endif
 }
 
+void marlin_server_settings_save_bed_pid(void) {
+    eeprom_set_var(EEVAR_PID_BED_P, variant8_flt(Temperature::temp_bed.pid.Kp));
+    eeprom_set_var(EEVAR_PID_BED_I, variant8_flt(Temperature::temp_bed.pid.Ki));
+    eeprom_set_var(EEVAR_PID_BED_D, variant8_flt(Temperature::temp_bed.pid.Kd));
+}
+
+void marlin_server_settings_save_noz_pid(void) {
+#if ENABLED(PIDTEMP)
+    eeprom_set_var(EEVAR_PID_NOZ_P, variant8_flt(Temperature::temp_hotend[0].pid.Kp));
+    eeprom_set_var(EEVAR_PID_NOZ_I, variant8_flt(Temperature::temp_hotend[0].pid.Ki));
+    eeprom_set_var(EEVAR_PID_NOZ_D, variant8_flt(Temperature::temp_hotend[0].pid.Kd));
+#endif
+}
+
 void marlin_server_settings_load(void) {
     (void)settings.reset();
 #if HAS_BED_PROBE

src/common/marlin_server.h

@@ -55,6 +55,8 @@ extern int marlin_server_inject_gcode(const char *gcode);
 
 // direct call of settings.save()
 extern void marlin_server_settings_save(void);
+extern void marlin_server_settings_save_bed_pid(void);
+extern void marlin_server_settings_save_noz_pid(void);
 
 // direct call of settings.load()
 extern void marlin_server_settings_load(void);

src/marlin_stubs/gcode.cpp

@@ -3,6 +3,7 @@
 #include "../../lib/Marlin/Marlin/src/gcode/queue.h"
 
 #include "PrusaGcodeSuite.hpp"
+#include "../common/marlin_server.h"
 
 #include "M330.h"
 #include "M50.hpp"
@@ -22,6 +23,30 @@ bool GcodeSuite::process_parsed_command_custom(bool no_ok) {
             PrusaGcodeSuite::M300();
             if (!no_ok) queue.ok_to_send();
             return true;
+        case 301:
+            M301();
+            marlin_server_settings_save_noz_pid();
+            if (!no_ok) queue.ok_to_send();
+            return true;
+        case 303: {
+            M303();
+            const int16_t e = parser.intval('E');
+            const bool u = parser.boolval('U');
+            if (u) {
+                if (e == -1)
+                    marlin_server_settings_save_bed_pid();
+                else if (e == 0)
+                    marlin_server_settings_save_noz_pid();
+            }
+            if (!no_ok)
+                queue.ok_to_send();
+            return true;
+        }
+        case 304:
+            M304();
+            marlin_server_settings_save_bed_pid();
+            if (!no_ok) queue.ok_to_send();
+            return true;
 #if defined(_DEBUG)
         case 330:
             PrusaGcodeSuite::M330();