add pcnt.rst

docs/api/pcnt.rst

@@ -1,3 +1,25 @@
+PCNT
+========
+
+Overview
+--------
+
+The PCNT (Pulse Counter) module is designed to count the number of rising and/or falling edges of an input signal. Each pulse counter unit has a 16-bit signed counter register and two channels that can be configured to either increment or decrement the counter. Each channel has a signal input that accepts signal edges to be detected, as well as a control input that can be used to enable or disable the signal input. The inputs have optional filters that can be used to discard unwanted glitches in the signal.
+
+Application Example
+-------------------
+
+PCNT counter with control signal and event interrupt example: `examples/12_pcnt <https://github.com/espressif/esp-idf/tree/master/examples/12_pcnt>`_.
+
+API Reference
+-------------
+
+Header Files
+^^^^^^^^^^^^
+
+  * `driver/pcnt.h <https://github.com/espressif/esp-idf/blob/master/components/driver/include/driver/pcnt.h>`_
+
+
 Macros
 ^^^^^^