PWM: Blink LED
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Overview
========
This is a sample app which blinks a LED using PWM.
The LED will start at a blinking frequency of 0.5Hz. Every 4 seconds,
the blinking frequency will double. When the blinking frequency
reaches 500Hz, the blinking frequency will be halved every 4 seconds
until the blinking frequency reaches 0.5Hz. This completes a whole
blinking cycle. From now on, the LED will repeat the blinking cycle
for ever.
Wiring
======
Arduino 101 and Quark D2000 CRB
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You will need to connect the LED to ground and PWM0 via the shield.
You may need a current limiting resistor. See your LED datasheet.
Nucleo_F401RE and Nucleo_L476RG
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Connect PWM2(PA0) to LED
Nucleo_F103RB
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Connect PWM1(PA8) to LED
Building and Running
====================
This sample can be built for multiple boards, in this example we will build it
for the arduino_101 board:
.. code-block:: console
$ cd samples/basic/blink_led
$ make BOARD=arduino_101
$ make BOARD=arduino_101 flash
After flashing the image to the board, the user LED on the board should start to
blinking as discussed in overview
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