verify_heater: Add initial support for verifying heaters and sensors

Add runtime checks to heaters and temperature sensors to check for
possible hardware faults.

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

klippy/extras/verify_heater.py

@@ -0,0 +1,67 @@
+# Heater/sensor verification code
+#
+# Copyright (C) 2018  Kevin O'Connor <kevin@koconnor.net>
+#
+# This file may be distributed under the terms of the GNU GPLv3 license.
+import logging
+import extruder
+
+class HeaterCheck:
+    def __init__(self, config):
+        self.printer = config.get_printer()
+        self.heater_name = config.get_name().split()[1]
+        self.heater = None
+        self.hysteresis = config.getfloat('hysteresis', 4., above=0.)
+        self.check_time = config.getfloat('check_time', 10., minval=1.)
+        self.heating_gain = config.getfloat('heating_gain', 2., above=0.)
+        default_gain_time = 20.
+        if self.heater_name == 'heater_bed':
+            default_gain_time = 60.
+        self.check_gain_time = config.getfloat(
+            'check_gain_time', default_gain_time, minval=1.)
+        self.met_target = False
+        self.last_target = self.goal_temp = 0.
+        self.fault_systime = self.printer.get_reactor().NEVER
+    def printer_state(self, state):
+        if state == 'connect':
+            self.heater = extruder.get_printer_heater(
+                self.printer, self.heater_name)
+            logging.info("Starting heater checks for %s", self.heater_name)
+            reactor = self.printer.get_reactor()
+            reactor.register_timer(self.check_event, reactor.NOW)
+    def check_event(self, eventtime):
+        temp, target = self.heater.get_temp(eventtime)
+        if temp >= target - self.hysteresis:
+            # Temperature near target - reset checks
+            if not self.met_target:
+                logging.info("Heater %s within range of %.3f",
+                             self.heater_name, target)
+            self.met_target = True
+            self.fault_systime = eventtime + self.check_time
+        elif self.met_target:
+            if target != self.last_target:
+                # Target changed - reset checks
+                logging.info("Heater %s approaching new target of %.3f",
+                             self.heater_name, target)
+                self.met_target = False
+                self.goal_temp = temp + self.heating_gain
+                self.fault_systime = eventtime + self.check_gain_time
+            elif eventtime >= self.fault_systime:
+                # Failure due to inability to maintain target temperature
+                return self.heater_fault()
+        elif temp >= self.goal_temp:
+            # Temperature approaching target - reset checks
+            self.goal_temp = temp + self.heating_gain
+            self.fault_systime = eventtime + self.check_gain_time
+        elif eventtime >= self.fault_systime:
+            # Failure due to inability to approach target temperature
+            return self.heater_fault()
+        self.last_target = target
+        return eventtime + 1.
+    def heater_fault(self):
+        logging.error("Heater %s not heating at expected rate", self.heater_name)
+        self.printer.invoke_shutdown("Heater %s failsafe" % (self.heater_name,))
+        return self.printer.get_reactor().NEVER
+
+def load_config_prefix(config):
+    return HeaterCheck(config)