pid_calibrate: Update the heater's target temperature during calibration

Update the target temperature during the pid calibration.  This gives
additional feedback to the user and it makes it less likely that a
verify_heater error will be raised during calibration.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

klippy/extras/pid_calibrate.py

@@ -24,7 +24,7 @@ class PIDCalibrate:
         except self.printer.config_error as e:
             raise self.gcode.error(str(e))
         print_time = self.printer.lookup_object('toolhead').get_last_move_time()
-        calibrate = ControlAutoTune(heater)
+        calibrate = ControlAutoTune(heater, target)
         old_control = heater.set_control(calibrate)
         try:
             heater.set_temp(print_time, target)
@@ -45,9 +45,10 @@ class PIDCalibrate:
 TUNE_PID_DELTA = 5.0
 
 class ControlAutoTune:
-    def __init__(self, heater):
+    def __init__(self, heater, target):
         self.heater = heater
         self.heater_max_power = heater.get_max_power()
+        self.calibrate_temp = target
         # Heating control
         self.heating = False
         self.peak = 0.
@@ -70,10 +71,11 @@ class ControlAutoTune:
         if self.heating and temp >= target_temp:
             self.heating = False
             self.check_peaks()
-        elif (not self.heating
-              and temp <= target_temp - TUNE_PID_DELTA):
+            self.heater.alter_target(self.calibrate_temp - TUNE_PID_DELTA)
+        elif not self.heating and temp <= target_temp:
             self.heating = True
             self.check_peaks()
+            self.heater.alter_target(self.calibrate_temp)
         if self.heating:
             self.set_pwm(read_time, self.heater_max_power)
             if temp < self.peak:

klippy/heater.py

@@ -105,6 +105,10 @@ class Heater:
             self.control = control
             self.target_temp = 0.
         return old_control
+    def alter_target(self, target_temp):
+        if target_temp:
+            target_temp = max(self.min_temp, min(self.max_temp, target_temp))
+        self.target_temp = target_temp
     def stats(self, eventtime):
         with self.lock:
             target_temp = self.target_temp