thermocouple: Add initial support for common SPI temperature sensing chips

Signed-off-by: Petri Honkala <cruwaller@gmail.com>
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

config/example-extras.cfg

@@ -631,6 +631,38 @@
 #   measurements must be provided.
 
 
+# MAXxxxxx serial peripheral interface (SPI) temperature based
+# sensors. The following parameters are available in heater sections
+# that use one of these sensor types.
+#[extruder]
+# See the "extruder" section in example.cfg for a description of
+# heater parameters. The parameters below describe sensor parameters.
+#sensor_type:
+#   One of "MAX6675", "MAX31855", "MAX31856", or "MAX31865".
+#spi_mode:
+#   The SPI mode to use when communicating with the chip. This
+#   parameter must be provided.
+#spi_speed:
+#   The SPI speed (in hz) to use when communicating with the chip.
+#   This parameter must be provided.
+#sensor_pin:
+#   The chip select line for the sensor chip. This parameter must be
+#   provided.
+#tc_type: K
+#tc_use_50Hz_filter: False
+#tc_averaging_count: 1
+#   The above parameters control the sensor parameters of MAX31856
+#   chips.  The defaults for each parameter are next to the parameter
+#   name in the above list.
+#rtd_nominal_r: 100
+#rtd_reference_r: 430
+#rtd_num_of_wires: 2
+#rtd_use_50Hz_filter: False
+#   The above parameters control the sensor parameters of MAX31865
+#   chips.  The defaults for each parameter are next to the parameter
+#   name in the above list.
+
+
 # G-Code macros (one may define any number of sections with a
 # "gcode_macro" prefix).
 #[gcode_macro my_cmd]

config/example.cfg

@@ -147,8 +147,9 @@ heater_pin: ar10
 sensor_type: EPCOS 100K B57560G104F
 #   Type of sensor - this may be "EPCOS 100K B57560G104F", "ATC
 #   Semitec 104GT-2", "NTC 100K beta 3950", "Honeywell 100K
-#   135-104LAG-J01", "NTC 100K MGB18-104F39050L32", "AD595", or "PT100
-#   INA826". Additional sensor types may be available - see the
+#   135-104LAG-J01", "NTC 100K MGB18-104F39050L32", "AD595", "PT100
+#   INA826", "MAX6675", "MAX31855", "MAX31856", or "MAX31865".
+#   Additional sensor types may be available - see the
 #   example-extras.cfg file for details. This parameter must be
 #   provided.
 sensor_pin: analog13