Add PN532 On Tag Trigger (#57)

esphomeyaml/components/pn532.rst

@@ -42,6 +42,8 @@ Configuration variables:
 - **update_interval** (*Optional*, :ref:`config-time`): The duration of each scan on the PN532. This affects the
   duration that the individual binary sensors stay active when they're found.
   If a device is not found within this time window, it will be marked as not present. Defaults to 1s.
+- **on_tag** (*Optional*, :ref:`Automation <automation>`): An automation to perform
+  when a tag is read. See :ref:`pn532-on_tag`.
 - **spi_id** (*Optional*, :ref:`config-id`): Manually specify the ID of the :ref:`SPI Component <spi>` if you want
   to use multiple SPI buses.
 - **id** (*Optional*, :ref:`config-id`): Manually specify the ID for this component.
@@ -52,6 +54,28 @@ Configuration variables:
 
     Example for hooking up the PN532 via SPI. Notice the position of the two switches on the right.
 
+.. _pn532-on_tag:
+
+``on_tag``
+----------
+
+This automation will be triggered when the PN532 module responds with a tag. Please note that this
+can be called quite often (with an interval of ``update_interval``) as it's triggered repeatedly
+if the tag is re-read many times.
+
+The parameter ``x`` this trigger provides is of type ``std::string`` and is the tag UID in the format
+``74-10-37-94``. The configuration below will for example publish the tag ID on the MQTT topic ``pn532/tag``.
+
+.. code:: yaml
+
+    pn532:
+      # ...
+      on_tag:
+        then:
+          - mqtt.publish:
+              topic: pn532/tag
+              payload: !lambda 'return x;'
+
 See Also
 --------
 

esphomeyaml/guides/automations.rst

@@ -303,6 +303,7 @@ All Triggers
 - :ref:`esphomeyaml.on_boot <esphomeyaml-on_boot>`
 - :ref:`esphomeyaml.on_shutdown <esphomeyaml-on_shutdown>`
 - :ref:`esphomeyaml.on_loop <esphomeyaml-on_loop>`
+- :ref:`pn532.on_tag <pn532-on_tag>`
 
 All Actions
 -----------