ATmega328P Arduino Compatible Nano V3 with USB cable.
An easy to use tool for reading and chaning the BLHeli parameters on your ESC’s. With just a few steps you can program this tool for use with speedcontrollers that have either a SimonK or BLHeli booloader flashed.
My BLHeli is setup with PWM Freq/Damped – Damped Light 
A quick guide for using this programmer can be found here: Programming an Arduino Nano for BLHeli