Fix #5

Author: matsujirushi

platformio.ini

@@ -9,7 +9,7 @@
 ; https://docs.platformio.org/page/projectconf.html
 
 [env:seeed_wio_terminal]
-platform = atmelsam
+platform = atmelsam@5.1.1
 board = seeed_wio_terminal
 framework = arduino
 platform_packages = framework-arduino-samd-seeed@https://github.com/Seeed-Studio/ArduinoCore-samd.git#v1.8.1