https://devzone.nordicsemi.com/f/nordic-q-a/8753/nrf51-dk-boardHello I have connected the nrF51-DK board and it was recognized by the computer. I have managed to put in in a boot loader mode. Since I switched it to boot loader mode the led, LD5 does not turn on any more, only when I putt the board into booten-USTelligent Community 13Mon, 17 Aug 2015 12:26:25 GMThttps://devzone.nordicsemi.com/thread/32092?ContentTypeID=1Mon, 17 Aug 2015 12:26:25 GMT137ad170-7792-4731-bb38-c0d22fbe4515:a969ab9d-43bc-400e-9f36-b42de1c6091eHung Bui<p>Hi Aran,</p> <p>I assume the bootloader mode you mentioned is the mode you enter when holding IF BOOT/RESET button when power on the board. That mode is used to switch between Segger Jlink and Mbed interface of the board.</p> <p>If you want to simply flash the application hex file you should not use this mode. Keep it in the Segger Jlink mode ( when the JLINK driver appear in My Computer as a hard driver). And you can either drag and drop the hex file to JLINK driver or use nRFGo Studio/Keil to program it. Please follow the getting started in the SDK documentation.</p> <p>If you want to switch between JLINK and MBED, you should use the binary file provided <a href="http://www.nordicsemi.com/eng/Products/nRF51-DK">here</a>. Look for nRF51-DK-J-Link-IF and nRF51-DK-mbed-IF in Download tab.</p><div style="clear:both;"></div>