Problem with J-link edu mini and NRF52 Dongle software loading

[dragilla]

Hi,

Just today my J-link EDU mini - NRF52 donlge combo stopped working. I do the following:

1. nrfjprog.exe --recover

2. nrfjprog.exe --eraseall

3. I use J-Flash lite to program the bootloader for NRF52-Dongle

Normally now the device should be available for programming from the uVision software. Now I can program, there are no errors, but after programming, the device is silent. When I take it off the usb port, and disconnect the debugger, and connect the dongle back in - it's in the bootloader mode (i think) - the red led is slowly blinking.

To make the program work I have to start the nRF Connect - Programmer and transfer the hex file onto the device manually. Then it works.

If I try to program the device from the uVision again or start a debug session, the device goes back to being silent (red led blinking after removal and reinsert to usb).

Also sometimes when I reconnect my RTT viewer on an already working app it also causes the dongle to go to the "red blinking" mode. But not alwayd. Go figure.

There was no physical damage to either dongle or the debugger and it all worked perfectly until today. 

Can I try anything to fix it? Is something permanently broken? 

I don't have another set (dongle+debuger) to play with and find the faulty elelement :(

[dragilla]

After such unsuccesful floash download in uvision, build log says: 

Erase Done.
Programming Done.
Verify OK.
Flash Load finished at 23:04:07

And then in nRF Connect - Programmer I can see only the bootloader - the application was not loaded :(

[dragilla]

Ok. Another observation - finally a pattern.

When I stop the RTT connection - then I can program via uVision and the program start afterwards. But then there is a problem to connect to RTT again. because it works only 1 in 10 tries. The other 9, I get the annoying blinking red led.

PS: another observation: when RTT viewer is connected and I take the dongle out, the red led on the dongle keeps blinking... like the dongle is powered via the debugger? I think this is causing the problem. I only don't understand how this could have worked from the beginning... 

Maybe I connected my debugger in the wrong way from the begining and now something has broken?

Please advise, thanks 

[dragilla]

Ok. I think I know what I did wrong. I accidently soldered the SB1 bridge next to the SWD connector. 

https://infocenter.nordicsemi.com/index.jsp?topic=%2Fug_nrf52840_dongle%2FUG%2Fnrf52840_Dongle%2Fhw_power_supply.html

It worked for a while and something failed as a result. Can you guess what could have happened and if I can fix it? 

I desoldered the bridge but my the problems remain.

[Amanda Hsieh]

Hi, 

This seems a bit chaotic, so I am not sure about everything. But first of all, the fact that you sometimes need to program via the nRF Connect programmer app makes sense. The bootloader will check bootloader settings for a CRC and flag indicating that the app is valid. So if you keep the bootloader but don't update the bootloader setting (which happens automatically during a USB DFU), then the bootloader will not start the app, but enter DFU mode. Also, the bootloader in the dongle will enter DFU mode if there has been a pin reset. Could it be that you modified HW tampers with the reset line? You may be seeing both these two issues at different times. 

-Amanda H.

[dragilla]

Thank you for your answer. The dongle is clearly broken :( I can still use it through nRF Connect or through J-Flash Lite but starting an app through uVision and viewing logs through RTT rarely works (sometimes it does, but it's not clear why and when).

The SB1 and SB2 were soldered at the same time for a while and I think it broke it. Now I desoldered SB1 but it doesn't help. So for now I think there is nothing I can do?