Custom board SWD programming with nrf52-dk

RE: Custom board SWD programming with nrf52-dk

Håkon Alseth — Wed, 26 Aug 2026 11:41:48 GMT

Hi,

[quote user="krf"]any update?[/quote]

It does not help to bump a thread less than 16 hours since your last update.

Q1: Do you have any other nRF DK's to use as a programmer?

Q2: If no; You have one of these cables, correct?

Could you connect this on your nRF52-DK, from P19 (Debug out) to P18 (Debug in), to verify that the DK itself switches the debug port correctly?

If you are then able to flash/erase/connect to the on-board nRF52832 device, then that has been verified.

Kind regards,

Håkon

RE: Custom board SWD programming with nrf52-dk

krf — Wed, 26 Aug 2026 08:26:51 GMT

any update?

RE: Custom board SWD programming with nrf52-dk

krf — Tue, 25 Aug 2026 16:29:04 GMT

Håkon Alseth After new board (same custom pcb but just newly swd header wires soldered), i examined swd lines with oscilloscope and find out pulses at swdio but nothing in swclk. Even if i plug out custom board from dk's P20( but keeping VTG to 3V) behavior is same. As i know host(DK) must sent clock pulses before swdio line communication start but it doesn't even try it.

And i tried it with VTG unplugged, so i can observe on-board nrf52832 swd communcaition and yes swclk starts very early (almost 50+ cycles) as expected.

So do you have any suggest?

RE: Custom board SWD programming with nrf52-dk

krf — Tue, 25 Aug 2026 10:59:37 GMT

Håkon Alseth I supplied my custom board with external supply and connect that supply also to VTG. I used it as input already and also i supplied custom board from dk itself with VTG is connected to DK's VDD but let me try other boards too.

RE: Custom board SWD programming with nrf52-dk

Håkon Alseth — Tue, 25 Aug 2026 10:55:14 GMT

Hi,

VTG shall be connected to your custom boards VDD. VTG is an input, seen from the programmer, to select the correct debug port (P20 in your case).

You should power your custom board from the nRF52-DK, ie. with 3.0V.

[quote user="krf"]

Q2: I didn't yet try it with another board but i will try it.

Also i want to mention it P19 select pin is at 3V when i left it float. Is it problem?

[/quote]

Please see here on how to connect on P20:

https://docs.nordicsemi.com/r/bundle/ug_nrf52832_dk/page/ug/dk/ext_programming_support_p20.html

And here on P19:

https://docs.nordicsemi.com/r/bundle/ug_nrf52832_dk/page/ug/dk/ext_programming_support_p19.html

SWD0_SELECT must be grounded.

[quote user="krf"]I didn't yet try it with another board but i will try it.[/quote]

Yes, please test with more than one custom board to see if the behaviour changes.

Kind regards,

Håkon

RE: Custom board SWD programming with nrf52-dk

krf — Tue, 25 Aug 2026 10:26:56 GMT

Håkon Alseth

Q1: When i supplied my custom board with 3V, i connect this pins to P20 of DK. I didn't want to send picture because i don't believe it would be observable (bunch of jumpers there are...). Here is the pins of custom board programming header: Vsupply, GND, SWO, N_RESET, SWCLK, SWDIO. Do not be stuck on for MCU_2V5_L label whole mcu supply seperated by headers and those whole tests made with seperated supply line!

Q2: I didn't yet try it with another board but i will try it.

Also i want to mention it P19 select pin is at 3V when i left it float. Is it problem?

Note: With this board there was 1uF cap on reset line which makes reset line unstable with first tryings ( It was stall at different voltages like 1.25V, 0.78V etc.) . After removing cap now reset line is stable at 3V but i suspect it if somehow it might be broke chip. Is it possible?

RE: Custom board SWD programming with nrf52-dk

Håkon Alseth — Tue, 25 Aug 2026 10:14:43 GMT

Hi,

The errors you are seeing points towards a incorrect connection to the external board.

[quote user="krf"]

DEC3 pin is at 3V

DEC2 is at 1.26V

DEC4 is at 1.26V

DEC1 is at 1.09V

[/quote]

These are all within the expected area, assuming VDD=3.0V.

Q1: Can you please share a picture on how you've setup the connection from DK to custom board?

Q2: Does this occur on more than one board?

Kind regards,

Håkon

RE: Custom board SWD programming with nrf52-dk

krf — Tue, 25 Aug 2026 10:11:29 GMT

İ verified that if i left VTG unconnected onboard nrf52832 flashed otherwise P19 or P20 selected. I left unconnected p19 and suspect about it. Somehow P19 can be selected? I use P20 connector

RE: Custom board SWD programming with nrf52-dk

krf — Tue, 25 Aug 2026 10:09:11 GMT

PaKa Yes i did and specified it in my question. VTG, SWDIO, SWCLK, RESET, GND , VDD. Also i tried both - external supply for custom board and supply from nrf52 dk VDD.

RE: Custom board SWD programming with nrf52-dk

PaKa — Tue, 25 Aug 2026 09:35:26 GMT

There are several more lines needed to program external targets, have you added all these? You can see which ones in the DK HW user guide. All lines listed are required, not only the 2 SWD lines.

RE: Custom board SWD programming with nrf52-dk

krf — Tue, 25 Aug 2026 09:17:56 GMT

Also :

DEC3 pin is at 3V

DEC2 is at 1.26V

DEC4 is at 1.26V

DEC1 is at 1.09V

when i supply VDD pins with 3V