https://devzone.nordicsemi.com/f/nordic-q-a/30265/nrf52-dk-flashing-app-on-external-moduleI use Adafruit Bluefruit library and developing code to run on Fanstell BT832. Up to know i have been able to compile several examples and run it on the NRF52 DK board. I have only used their Serial DFU bootloader that work well on DK board. Nowen-USTelligent Community 13Wed, 07 Feb 2018 15:02:23 GMThttps://devzone.nordicsemi.com/thread/120137?ContentTypeID=1Wed, 07 Feb 2018 15:02:23 GMT137ad170-7792-4731-bb38-c0d22fbe4515:04dd3ce2-86b8-488a-93b1-f41c75fabb21tesc<p>Hi,</p> <p>UART communication requires a USB to UART bridge between the PC and the nRF. On the DK, the interface MCU acts as USB to UART bridge, and the UART end is connected to GPIO pins 5-8 on the nRF. This is where your serial (UART) communication goes when you use the COM port for the DK on the PC.</p> <p>You can use the same bridge for the external board as well, if you connect P0.05, ..6, ..7 and ..8 to the corresponding pins for RTS, TXD, CTS and RXD on the custom board. Make sure to unprogram (erase flash on) the on-DK nRF first, for it not to meddle with the UART lines.</p> <p>Similarly, for the buttons, reset, etc., you must do that on the external board. The buttons, LEDs, etc on the DK are connected to the on-DK nRF.</p> <p>If for instance you were talking UART to the on-DK nRF, but tried to set the external board into DFU mode, then that would explain the DFU serial error message.</p> <p>Regards,<br />Terje</p><div style="clear:both;"></div>