simple PWM

Revision:
0:b166a4d08fd6
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed-os.lib	Wed Feb 10 02:45:37 2021 +0000
@@ -0,0 +1,1 @@
+https://github.com/ARMmbed/mbed-os/#485bdeee150e2bc8ed75e27d936060fb63a7a7d1