Only one instance of the HART Master can be running (via htest or any DLL test or Application Layer test) at a time on the HART Test System. If htest or any DLL test or Application Layer test is running from one linux terminal, another CAL/DLL/UAL test or htest cannot be executed from another terminal.
Before starting any test or invoking htest, make sure that the HART Master is not running in another terminal that is minimized, hidden or forgotten. If you are not sure whether multiple copies of the HART Master are running, reboot the HART Test System for a clean start and and then start your testing.
Please note that TDMA layer tests (TML) can also not be run on a wirelessHART device from a terminal if any DLL test, Application Layer test or htest is running on the HART Test System from another terminal.