Read hardware counter example
=============================

Code
----

.. code:: python

   start_counter();
   while : read_counter() < 200000000 {
       digital_write(4, true);
   }
   stop_counter();

-  Following code works on PocketBeagle, to use on other boards, please
   change the pins accordingly.

Explanation
------------

Since, PRU's hardware counter works at 200 MHz, it counts up to 2 x 108
cycles in 1 second. So, this can be reliably used to count time without
using ``delay``, as we can find exactly how much time 1 cycle takes.

| 2 x 108 cycles/second.
| 1 Cycles = 0.5 x 10-8 seconds.

So, it can be used to count how many cycles have passed since, say we
received a high input on pin 3. ``start_counter`` starts the counter,
and ``read_counter`` reads the current state of the counter, and
``stop_counter`` stops the counter.