thermistor: Add support for defining custom thermistors

Add the ability to define a new thermistor type in the config file.

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

3 files changed, 54 insertions, 2 deletions

diff --git a/config/example-extras.cfg b/config/example-extras.cfg
index a28654f7..e67f7165 100644
--- a/config/example-extras.cfg
+++ b/config/example-extras.cfg
@@ -394,6 +394,31 @@
 #   provided when using an st7920 display.
 
 
+# Custom thermistors (one may define any number of sections with a
+# "thermistor" prefix).  A custom thermistor may be used in the
+# sensor_type field of a heater config section. (For example, if one
+# defines a "[thermistor my_thermistor]" section then one may use a
+# "sensor_type: my_thermistor" when defining a heater.) Be sure to
+# place the thermistor section in the config file above its first use
+# in a heater section.
+#[thermistor my_thermistor]
+#temperature1:
+#resistance1:
+#temperature2:
+#resistance2:
+#temperature3:
+#resistance3:
+#   Three resistance measurements (in Ohms) at the given temperatures
+#   (in Celsius). The three measurements will be used to calculate the
+#   Steinhart-Hart coefficients for the thermistor.  These parameters
+#   must be provided when using Steinhart-Hart to define the
+#   thermistor.
+#beta:
+#   Alternatively, one may define temperature1, resistance1, and beta
+#   to define the thermistor parameters. This parameter must be
+#   provided when using "beta" to define the thermistor.
+
+
 # Replicape support - see the generic-replicape.cfg file for further
 # details.
 #[replicape]
diff --git a/config/example.cfg b/config/example.cfg
index ae8c3b9a..9d860a58 100644
--- a/config/example.cfg
+++ b/config/example.cfg
@@ -146,8 +146,9 @@ heater_pin: ar10
 #   periods) to the heater. The default is 1.0.
 sensor_type: EPCOS 100K B57560G104F
 #   Type of sensor - this may be "EPCOS 100K B57560G104F", "ATC
-#   Semitec 104GT-2", "NTC 100K beta 3950", or "AD595". This parameter
-#   must be provided.
+#   Semitec 104GT-2", "NTC 100K beta 3950", or "AD595". Additional
+#   sensor types may be available - see the example-extras.cfg file
+#   for details. This parameter must be provided.
 sensor_pin: analog13
 #   Analog input pin connected to the sensor. This parameter must be
 #   provided.
diff --git a/klippy/extras/thermistor.py b/klippy/extras/thermistor.py
index 22836379..cc2d64fd 100644
--- a/klippy/extras/thermistor.py
+++ b/klippy/extras/thermistor.py
@@ -77,6 +77,27 @@ class Thermistor:
         r = math.exp(ln_r)
         return r / (self.pullup + r)
 
+# Custom defined thermistors from the config file
+class CustomThermistor:
+    def __init__(self, config):
+        self.name = " ".join(config.get_name().split()[1:])
+        t1 = config.getfloat("temperature1", minval=KELVIN_TO_CELCIUS)
+        r1 = config.getfloat("resistance1", minval=0.)
+        beta = config.getfloat("beta", None, above=0.)
+        if beta is not None:
+            self.params = {'t1': t1, 'r1': r1, 'beta': beta}
+            return
+        t2 = config.getfloat("temperature2", minval=KELVIN_TO_CELCIUS)
+        r2 = config.getfloat("resistance2", minval=0.)
+        t3 = config.getfloat("temperature3", minval=KELVIN_TO_CELCIUS)
+        r3 = config.getfloat("resistance3", minval=0.)
+        (t1, r1), (t2, r2), (t3, r3) = sorted([(t1, r1), (t2, r2), (t3, r3)])
+        self.params = {'t1': t1, 'r1': r1, 't2': t2, 'r2': r2,
+                       't3': t3, 'r3': r3}
+    def create(self, config):
+        return Thermistor(config, self.params)
+
+# Default sensors
 Sensors = {
     "EPCOS 100K B57560G104F": {
         't1': 25., 'r1': 100000., 't2': 150., 'r2': 1641.9,
@@ -93,3 +114,8 @@ def load_config(config):
     for sensor_type, params in Sensors.items():
         func = (lambda config, params=params: Thermistor(config, params))
         pheater.add_sensor(sensor_type, func)
+
+def load_config_prefix(config):
+    thermistor = CustomThermistor(config)
+    pheater = config.get_printer().lookup_object("heater")
+    pheater.add_sensor(thermistor.name, thermistor.create)