Do you want to debug an NXP Kinetis Freedom board using the P&E Micro GDB-server with Open-SDA? If so, I recommend you watch this video tutorial that show you how to configure this in the correct way!
How does a Atollic TrueSTUDIO user debug an mbed device equipped with an on-board OpenSDA debugger? There are several ways and it depends on which firmware that is loaded on to the OpenSDA debugger.
Three widely used OpenSDA firmware choices are: CMSIS-DAP, P&E Micro, SEGGER
This blog article will provide an instruction on getting started with OpenSDA/CMSIS-DAP using TrueSTUDIO and the open-source PyOCD GDB-server.