Running shell script from within the DialPlan

Hi,
The tdtool command sends a command to a USB device that initiates operation of a remote switch. The application and hardware are matched.

If I uncomment lines 2 and 3, I can place another USB device in the system , I can communicate directly via serial to an Arduino.

I thought about user permissions...
When I issue 'su asterisk' and launch the shell scripts they work as user asterisk and everything works fine from the CLI.

Thanks

Paul