NRF52840 DK - Programming external custom board at 3.3V

RE: NRF52840 DK - Programming external custom board at 3.3V

SwRa — Tue, 24 Mar 2026 09:57:56 GMT

Hello,

The voltage on the external board needs to match the DK while programming. ( It is okay to power the board differently under normal operation.) So I suggest that you keep the volage same as that of the DK only while programing/debugging.. If that is not suitable, then you can use alternative options to program your custom board, like a dedicated JLink programmer which supports 1.8V or the nRF54L15-DK. The nRF54L15 DK supports programming and debugging external nRF51, nRF52, nRF53, and nRF54 Series SoCs within a 1.8V–3.6V range. Hope that helps.

Best Regards,

Swathy

RE: NRF52840 DK - Programming external custom board at 3.3V

ign0 — Thu, 19 Mar 2026 22:06:41 GMT

Hi, sorry for interrupting here, but, if my custom board has 1v8 power on my nRF52833 and im using nRF52833-DK how can i program/debug the boards?

RE: NRF52840 DK - Programming external custom board at 3.3V

SwRa — Thu, 12 Feb 2026 15:00:17 GMT

Hello,

VIO_REF is the reference for GPIO/SWD I/O voltage. SB19 connects that external VIO_REF into the DK’s I/O domain so the debugger and GPIOs follow that voltage (within the allowed range). SB47 on nRF52‑series DKs is used when you want the DK to supply power out through P19; when SB47 is shorted, you must not also power the external board separately. See here: https://docs.nordicsemi.com/bundle/ug_nrf52840_dk/page/UG/dk/ext_programming_support_P19.html

Regards,

Swathy

RE: NRF52840 DK - Programming external custom board at 3.3V

bpolito8 — Wed, 11 Feb 2026 14:09:10 GMT

That makes sense, thank you.

Could you please provide some info or documentation about what VIO_REF does if connected to an external board through SB19/the P19 connector?

RE: NRF52840 DK - Programming external custom board at 3.3V

SwRa — Wed, 11 Feb 2026 12:53:04 GMT

Hello,

It is possible to use the DK to program an external hardware.. But they should operate at the same voltage during programming. 3V and 3.3V doesn't have that much of a difference, so it might work, but it is always recommended to power both the devices similarly to eliminate possible errors. Also note that they should have the same ground reference. The best approach is to use a level shifter in your circuit to adjust the voltage of the custom board to match that of the DK.

Regards,

Swathy