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>

4 files changed, 91 insertions, 4 deletions

diff --git a/config/example-extras.cfg b/config/example-extras.cfg
index 33b67178..fa48e780 100644
--- a/config/example-extras.cfg
+++ b/config/example-extras.cfg
@@ -122,6 +122,28 @@
 #   See the example.cfg for the definition of the above parameters.
 
 
+# Heater and temperature sensor verification. Heater verification is
+# automatically enabled for each heater that is configured on the
+# printer. Use verify_heater sections to change the default settings.
+#[verify_heater heater_config_name]
+#heating_gain: 2
+#   The minimum temperature (in Celsius) that the heater must increase
+#   by when approaching a new target temperature. The default is 2.
+#check_gain_time:
+#   The amount of time (in seconds) that the heating_gain must be met
+#   in before an error is raised. The default is 20 seconds for
+#   extruders and 60 seconds for heater_bed.
+#hysteresis: 4
+#   The difference between the target temperature and the current
+#   temperature for the heater to be considered within range of the
+#   target temperature. The default is 4.
+#check_time: 10
+#   The amount of time (in seconds) a heater that has reached the
+#   target temperature (as defined by the hysteresis field) may fall
+#   outside the target temperature range before an error is
+#   raised. The default is 10.
+
+
 # Multi-stepper axes. On a cartesian style printer, the stepper
 # controlling a given axis may have additional config blocks defining
 # steppers that should be stepped in concert with the primary
diff --git a/docs/Todo.md b/docs/Todo.md
index adf4c8c1..2c9be3c5 100644
--- a/docs/Todo.md
+++ b/docs/Todo.md
@@ -44,10 +44,6 @@ Safety features
    endstop detection is a good idea because of spurious signals caused
    by electrical noise.)
 
-* Support validating that heaters are heating at expected rates. This
-  can be useful to detect a sensor failure (eg, thermistor short) that
-  could otherwise cause the PID to command excessive heating.
-
 Testing features
 ================
 
diff --git a/klippy/extras/verify_heater.py b/klippy/extras/verify_heater.py
new file mode 100644
index 00000000..f7b750eb
--- /dev/null
+++ b/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)
diff --git a/klippy/heater.py b/klippy/heater.py
index d3315a52..0e854db7 100644
--- a/klippy/heater.py
+++ b/klippy/heater.py
@@ -141,6 +141,8 @@ class PrinterHeater:
         # pwm caching
         self.next_pwm_time = 0.
         self.last_pwm_value = 0.
+        # Load verify_heater module
+        printer.try_load_module(config, "verify_heater %s" % (self.name,))
     def set_pwm(self, read_time, value):
         if self.target_temp <= 0.:
             value = 0.