Reference firmware for PixArt's PMT9123 sensor and evaluation board. "Hello World" and "Library" contain the exact same files. Please import just one of the two into your mBed compiler as a new program and not as a library.

Revision:
0:71ff24e8c21e
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed-os.lib	Tue Apr 10 20:17:47 2018 +0000
@@ -0,0 +1,1 @@
+https://github.com/ARMmbed/mbed-os/#569159b784f70feaa32ce226aaca896fb83452f7