KINGKONG BLHeli USB Adaptor Unable to communicate with RacerStar RS40A V2 ESC

I ran into a problem recently where my KINGKONG BLHeli usb to ESC serial adaptor couldn't talk to my RacerStar RS40A V2 ESC.  Looking at the serial signal on the PPM pin, the voltage levels on the reply from the ESC wasn't swinging nicely down to 0V indicating the pullup resistor on the serial interface board might be a bit too strong.  

There is a 100 Ohm series resistor going to the SIG/PPM pin.

And a 3.3K pullup to +5V.  This is the resistor that needs to be changed.  I used a 6K 0402 resistor I had laying around and things worked like a champ.

Hope this was helpful to you out there.  Leave a comment if you have any questions or suggestions for future articles.

Thanks!

~pk