htu21d: Support for HTI21D family sensor on I2C bus (#2803)

Signed-off-by: Lucio Tarantino <lucio.tarantino@gmail.com>

config/sample-macros.cfg

@@ -147,3 +147,32 @@ gcode:
             printer[SENSOR].temperature,
             printer[SENSOR].pressure,
             printer[SENSOR].humidity))}
+
+######################################################################
+# HTU21D family Environmental Sensor
+######################################################################
+
+# The macro below assumes you have a HTU21D sensor_type defined in one
+# of the applicable sections in printer.cfg, such as:
+#
+#[temperature_sensor my_sensor]
+#sensor_type: HTU21D
+#
+# Note the format of the parameter SENSOR in the macro below.  The HTU21D
+# sensor status can be accessed using the format "htu21d <section_name>".
+# The example section above is named "my_sensor", thus the htu21d can be
+# queried as follows:
+#
+# QUERY_HTU21D SENSOR='htu21d my_sensor'
+#
+# Since a default parameter is defined one could simply enter QUERY_HTU21D
+# as well.
+
+[gcode_macro QUERY_HTU21D]
+default_parameter_SENSOR: htu21d my_sensor
+gcode:
+    {printer.gcode.action_respond_info(
+        "Temperature: %.2f C\n"
+        "Humidity: %.2f%%" % (
+            printer[SENSOR].temperature,
+            printer[SENSOR].humidity))}