nRF52840 Dongle not connecting to J-Link

RE: nRF52840 Dongle not connecting to J-Link

Einar Thorsrud — Fri, 22 Apr 2022 06:23:47 GMT

Yes, that hex file will set the voltage to 3.0 V.

RE: nRF52840 Dongle not connecting to J-Link

faskrobo — Fri, 22 Apr 2022 02:38:40 GMT

In the "Revert to production bootloader" section in nRF52840 Dongle Programming Tutorial, there's a zipped hex file. So would that set the voltage?

RE: nRF52840 Dongle not connecting to J-Link

Einar Thorsrud — Thu, 21 Apr 2022 19:34:24 GMT

Hi,

More hi end J-Link devices has a level shifter and will adjust the signal voltage to the measured VDD voltage. The J-Link EDU Mini however only supports about 3.3 V. So if this is what has happened (UICR has been erased and the device reset before re-writing REGOUT0 to configure for 3.0V), then this makes sense.

[quote user="faskrobo"]And is the voltage set in the hex file provided in the tutorial above? [/quote]

Which specific file are you referring to? Generally though, all projects in the SDK that is built for the nRF52840 Dongle as target will set the VDD voltage correctly.

[quote user="faskrobo"]Is there anything to be especially careful about when measuring voltage on an nRF dongle, and is there a way to bring back the first one or is it probably fried?[/quote]

It should be quite robust, but I cannot say how you would fix this (or if it is possible) without knowing what has happened and what has been damaged. I suggest just obtaining a new one instead of spending time troubleshooting if you believe you have damaged it, as this is a low-cost device.

RE: nRF52840 Dongle not connecting to J-Link

faskrobo — Thu, 21 Apr 2022 16:40:26 GMT

As a point of clarification, does the J-Link require the dongle to output 3.3V on VDD while the dongle is powered by a PC via USB? And is the voltage set in the hex file provided in the tutorial above? I tried to measure the VDD voltage using a multimeter, but somehow as a result of me touching probes to pins something broke and the device won't power on anymore. There's a second dongle that I tried however and it does connect fine. Is there anything to be especially careful about when measuring voltage on an nRF dongle, and is there a way to bring back the first one or is it probably fried?

RE: nRF52840 Dongle not connecting to J-Link

Einar Thorsrud — Tue, 19 Apr 2022 10:12:59 GMT

Hi,

What is the VDD voltage of the dongle? If the firmware has been replaced, it could be that the voltage out of REG0 is lower than expected (the default value of the nRF52840 IC is 1.8 V, while the firmware the dongle ships with sets it to 3.0 V). If it is 1.8 V, then I suspect the J-Link EDU Mini will not be able to communicate with it as it assumes 3.3 V (3.0 should be close enough, but not 1.8 V). If this is the problem then you either need to use a level shifter or a more high end debugger which has it included, or modify the dongle HW to increase the voltage. See Recover after an accidental UICR erase in the last part of nRF52840 Dongle Programming Tutorial for details.