Hello. If you want to run script from the Sum-PPM receiver, its possbile: assign a virtual channel to CMD chanel, than "Run script XX" to any of 3 CMD states. (in the RC tab). Another way is via Adjustable variables (see corresponding section in the manual)
"Trigger hardware pin" - I assume that it relates to script functionality and waht script can do, but not to how it can be started.