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)

[Simonr]

Hi Jimmy

Seems like you can scroll down in your ABOUT section to get to the Verbose Logging button on your end. Please try enabling it to see if that helps at all.

Are you sure the J-Link device you have bought supports programming devices down to 1.8V, as this is not a feature in all J-Link devices, some (including the debugger on our DKs) require a 3.0V voltage supplied on the target board, so my guess would be that you need to supply your device with 3V. Here's SEGGERs list of J-Link models and what voltages, etc. they support. Do you have any of these or some other device? https://www.segger.com/products/debug-probes/j-link/models/model-overview/ 

Best regards,

Simon

[Jimmyh]

Hi Simon

Finally, I know what the problem is. I have a broken cable between the Jlink device and the chip. When I replaced the broken wire, the connection worked.

I successfully connected to Jlink using Segger Embedded Studio and downloaded the code.

But when I connected to Jlink the same way again and tried to download the code, it got this error:

I'm sure the Jlink device is connected to the chip without problems (VDD, GND, SWD are connected correctly) because my other MCU works fine (connect Jlink multiple times and download the code).

I wonder what might be the cause of this error if Jlink connects correctly (why the first time it connects and downloads the code successfully, but the second time it fails)? While the Nreset pin is always low before and after successful connection, I wonder if this is normal.

Best regards