This is my experience to update Mini CN900, I hope it helps you.

 

Free Download Smart CN900 Mini 1.50.2.23 update tool with Win7 Win8 driver:

https://mega.nz/#!u2ATCSrB!7iQNPtXTyc5FTntJ_UtVhK6sD-feROXp1Vw02JTu7zY

Connect mini900 with laptop via USB cable

Open driver folder, install driver (for Win7 or Win8 system)

 

Next,find Computer on the desktop,Set com port to COM4

Run CN900 Mini firmware update tool on desktop

Press CONNECT

And click update

 

Next, click CN900 MINI, click update

 

The firmware has updated to the new version.

http://www.obd360.com/wholesale/smart-cn900-mini-transponder-key-programmer.html