Minimum connection for Jlink download

[Jimmyh]

hello!

I want to use Jlink to download code to a NRF52840 chip as MCU development board, but the number of pins and pin spacing of my Jlink are different from it. So I had to connect it to my Jlink with some separate wires. I wonder what is the minimum connection pin for nrf52840? Is it only VDD, SWDIO, SWCLK and one of GND that must be connected to Jlink? Or do SWO and NREST also have to be connected to Jlink in order to download code to nrf52840? I tried a few combinations, but they didn't work. I don't know whether it is the wiring or the Jlink problem.

Can someone help me, please?

(This is the interface)

[Mark Olsson]

GND is required (obviously)

VDD allows the jlink to know if the device is powered, so required

NRST allows the jlink to do a hardware reset, not technically required but makes things much more reliable if you use it. (Especially if you deep-sleep)

SWDIO/SWCLK are the programming pins, so required.

When you try to connect using 'nrf connect for desktop', do you get any output that might help us to debug the error?

[Mark Olsson]

SWO is for outputting debug messages, not required

[Jimmyh]

I tried to connect the chip with 'NRF Connect for Desktop' as you said. The following error is reported:

Does this mean there is something wrong with my Jlink?

[Simonr]

Hi

 Mark Olsson suggestion is correct, as GND, VDD and the SWD pins are the only required ones. Can you share some information on what J-Link device you're using specifically?

Also, what voltage are you powering your nRF52840 chip with, and how exactly is it connected to the J-Link? Is the nRF52840 chip a third party module or some custom board you have made yourself?

You can also try turning on Verbose Logging with the button in the image below for the nRF Programmer app so we might get more information on what the issue is.

Best regards,

Simon

[Jimmyh]

Hi, Simon

My NRF52840 is powered by 1.8V via USB. I did try to connect the four pins you mentioned. But it still doesn't work.

My device is based on NRF52840 as MCU. It's a product of Acconeer Radar.

I don't know any more information about my Jlink because I just bought it online from a middleman.

As for Verbose Logging, I don't seem to have as much information in my graph as you do.

I have consulted some engineers and they tend to think that it is the connection between Jlink and MCU except for the problem. But I checked it carefully many times and couldn't show the MCU information.

Here is some information about Jlink:

 Best regards，

Jimmy