Python Program for running Traxxas 3355R ESC

First of all thank you if you can help or lead me in the right direction! I’ve been working on this for the past 3 weeks, everyday and cannot resolve.

I am connecting from an RPI to an Adafruit 16 channel PWM to the Traxxas Stampede ESC 3355R. I have no problems controllng the steering or other servos with this configuration through a Python app. However, I cannot get the ESC to respond and I have no idea what the issue is or how I need to set the commands or the ESC to make this connection work.

Any thoughts, help is tremendously appreciated! I live in the Ventura County (Thousand Oaks area) CA if anyone lives near by, I would really like to work in person for an hour or so.

BTW: I tried the PixHawk method but get GPS and AHRS errors so never can get the PixHawk armed through mission planner and after countless calibration attempts, I gave up.