Add ability to modify PID parameters without a reload (#35)

* Add ability to set heater PID without on the fly

* Add docs for Set_HEATER_PID

* Fix line-length limit

Co-authored-by: Lasse Dalegaard <dalegaard@gmail.com>

docs/G-Codes.md

@@ -863,6 +863,11 @@ WRITE_FILE parameter is enabled, then the file /tmp/heattest.txt will
 be created with a log of all temperature samples taken during the
 test.
 
+#### SET_HEATER_PID
+`SET_HEATER_PID HEATER=<config_name> KP=<kp> KI=<ki> KD=<kd>`: Will
+allow one to manually change PID parameters of heaters without a 
+reload of the firmware.
+
 ### [pause_resume]
 
 The following commands are available when the

klippy/extras/heaters.py

@@ -74,6 +74,13 @@ def __init__(self, config, sensor):
             self.cmd_SET_HEATER_TEMPERATURE,
             desc=self.cmd_SET_HEATER_TEMPERATURE_help,
         )
+        gcode.register_mux_command(
+            "SET_HEATER_PID",
+            "HEATER",
+            self.name,
+            self.cmd_SET_HEATER_PID,
+            desc=self.cmd_SET_HEATER_PID_help,
+        )
 
     def set_pwm(self, read_time, value):
         if self.target_temp <= 0.0:
@@ -180,6 +187,21 @@ def cmd_SET_HEATER_TEMPERATURE(self, gcmd):
         pheaters = self.printer.lookup_object("heaters")
         pheaters.set_temperature(self, temp)
 
+    cmd_SET_HEATER_PID_help = "Sets a heater PID parameter"
+
+    def cmd_SET_HEATER_PID(self, gcmd):
+        if not isinstance(self.control, ControlPID):
+            raise gcmd.error("Not a PID controlled heater")
+        kp = gcmd.get_float("KP", None)
+        if kp is not None:
+            self.control.Kp = kp / PID_PARAM_BASE
+        ki = gcmd.get_float("KI", None)
+        if ki is not None:
+            self.control.Ki = ki / PID_PARAM_BASE
+        kd = gcmd.get_float("KD", None)
+        if kd is not None:
+            self.control.Kd = kd / PID_PARAM_BASE
+
 
 ######################################################################
 # Bang-bang control algo