This is an example program of WS2812 library https://developer.mbed.org/users/devararendy/code/WS2812/ in main program, i also put some line to measure how many asm NOP do we need. I have test it on STM32F411RE (Nucleo 411RE). if you would like to use another microcontroller, you need to adjust the asm("nop") in the library.

Dependencies:   USBDevice WS2812 mbed-os

Revision:
2:0d3906d69a41
Parent:
1:c18078160be3
--- a/WS2812.lib	Sat Dec 10 08:38:13 2016 +0000
+++ b/WS2812.lib	Sat Dec 10 09:21:00 2016 +0000
@@ -1,1 +1,1 @@
-https://developer.mbed.org/users/devararendy/code/WS2812/#f080cb888db6
+https://developer.mbed.org/users/devararendy/code/WS2812/#8910a1fcbdb0