https://devzone.nordicsemi.com/f/nordic-q-a/34327/programming-nrf51822-on-a-custom-board-using-nrf52840-dkHello, Is it possible to program nRF51822 with nRF52DK (PCA10056) ? Currently I am trying to program my custom beacon (nRF51822) connected via SWD P20 header. I am using SDK 12.3.0 and Keil uVision 5. I have tried to upload radio_test example fromen-USTelligent Community 13Tue, 15 May 2018 13:18:08 GMThttps://devzone.nordicsemi.com/thread/132056?ContentTypeID=1Tue, 15 May 2018 13:18:08 GMT137ad170-7792-4731-bb38-c0d22fbe4515:0ff3efa0-1391-4d8a-8146-c2a735c4b3dbEdvin<p>Hello,</p> <p>If your target info reads &quot;Device: nRF52840_xxAA&quot; it seems like the wiring is not done correctly.</p> <p>How have you connected the pins on P20?</p> <p>The pins you need to connect from P20 are VTG, SWDIO, SWDCLK and GND DETECT.</p> <p>SWDIO and GND DETECT are ok, as they can be connected directly, but remember that VTG and GND DETECT does not provide VDD to the external chip. They are used to check that the board is powered. You can power the device with an external battery, or with VDD and GND from the DK, and then connect VTG and GND DETECT to check that the board is actually powered. Once these pins detect a voltage on the external chip, it should switch from programming the internal nRF52840 to programming the nRF51 chip.</p> <p>&nbsp;</p> <p>Best regards,</p> <p>Edvin</p><div style="clear:both;"></div>