Recovery of Bricked Interface MCU on nRF52840 DK (PCA10056)

[Jay99]

I am using an nRF52840 DK (Version: 3.0.1). After a failed update/event, the DK is no longer recognized by my OS (Windows) via USB. LED5 blinks once when the usb is connected and then goes off. The mcu still works( last program I flashed I can see the output of it in a terminal)

Attempted Steps:

• Tried holding the Reset button while powering on (Bootloader mode) — No response.
• Tested different USB cables and ports — No change.

Request:

Is there a way to re-flash the interface MCU with the J-Link OB firmware?

I noticed the J-Link needle pins / test pads on the board and was wondering:

• Are these connected to the interface MCU?
• Is it possible to use them to recover or reprogram the interface firmware?

I couldn’t find clear documentation regarding this in the DK schematics or user guide.

[JONATHAN LL]

Hi,

You can download the DK hardware files from our product page on the DK, make sure to select the correct version corresponding to the one you have. 

noticed the J-Link needle pins / test pads on the board and was wondering:

The J4 interface is connected to the IMCU on the DK, the nRF5340 in this version. 

You can see this on page 3 in the schematics. 

Is there a way to re-flash the interface MCU with the J-Link OB firmware?

You could in use this to flash the IMCU as you could flash any nRF5340 device over the SWD interface. 

But I have not seen a case where the IMCUs firmware stops working so I suspect that something else is the root of this issue. 


Can you check voltage on the VBUS for the IMCU, on R13. 


What we do typical see is that the USB interface is damaged in some way. 

If you can its also possible to see this when probing the Data lines for the IMCU USB, there will be no activity. 


Regards,
Jonathan

[PaKa]

If you connect ANYTHING to the Interface MCU connector and programs the nRF5340 then the DK is for sure only trash. You can't recover the OBD through this interface!!!!!

Wanted to make sure no-one tries to use the IMCU connector as that will brick all DKs.

Most issues like this are faulty USB cables, issues with USB ports/hubs or incorrect SW versions on the PC. Start checking all these after checking hte VBUS voltage.

[Jay99]

Hey, Got it I'll try your suggestions and can you also please tell why I shouldn't flash the interface mcu, what else is there that reflashing it will break it.

[PaKa]

Because you won't get access to the code needed for the programming.

[Jay99]

I got the j link ob for nrf5340