add platformio file and fix compiling without IP

platformio.ini

@@ -0,0 +1,27 @@
+; PlatformIO Project Configuration File
+;
+;   Build options: build flags, source filter
+;   Upload options: custom upload port, speed and extra flags
+;   Library options: dependencies, extra library storages
+;   Advanced options: extra scripting
+;
+; Please visit documentation for the other options and examples
+; https://docs.platformio.org/page/projectconf.html
+
+[platformio]
+src_dir = examples/knx-demo
+
+
+[env]
+platform = atmelsam
+board = zeroUSB
+framework = arduino
+build_type = debug
+monitor_speed = 115200
+lib_ldf_mode = deep+
+lib_extra_dirs = 
+  ${sysenv.USERPROFILE}/Documents/PlatformIO/Projects
+build_flags = 
+  -Wno-unknown-pragmas 
+
+[env:build]