https://devzone.nordicsemi.com/f/nordic-q-a/19659/develop-with-nrf52-dk-and-mbedI started working with NRF52-dk. I develop with GCC compiler and mbed SDK (debugging with OpenOCD and GDB). On download (tools) page I see &quot;nRF5x-OB-mbed-IF&quot; with description: &quot;mbed Interface MCU Firmware for on-board debugger for nRF5x Development Toolsen-USTelligent Community 13Tue, 14 Feb 2017 13:15:19 GMThttps://devzone.nordicsemi.com/thread/76493?ContentTypeID=1Tue, 14 Feb 2017 13:15:19 GMT137ad170-7792-4731-bb38-c0d22fbe4515:cd444186-7d4f-48b1-a89b-f965317fc1deHung Bui<p>&quot;nRF5x-OB-mbed-IF&quot; is the firmware for the Segger debugger/programmer chip on our kit so it support flashing mbed image as mass storage driver. It&#39;s not very important now as it supported by default by Segger with our current DKs. If you use OpenOCD you don&#39;t have to worry ab that file.</p><div style="clear:both;"></div>