Merge upstream

examples/arduino-external-libs/README.md

@@ -0,0 +1,27 @@
+How to build PlatformIO based project
+=====================================
+
+1. [Install PlatformIO Core](http://docs.platformio.org/page/core.html)
+2. Download [development platform with examples](https://github.com/platformio/platform-raspberrypi/archive/develop.zip)
+3. Extract ZIP archive
+4. Run these commands:
+
+```shell
+# Change directory to example
+$ cd platform-raspberrypi/examples/arduino-external-libs
+
+# Build project
+$ pio run
+
+# Upload firmware
+$ pio run --target upload
+
+# Build specific environment
+$ pio run -e pico
+
+# Upload firmware for the specific environment
+$ pio run -e pico --target upload
+
+# Clean build files
+$ pio run --target clean
+```