J-Link from nRF52840-dk takes several minutes to come up when not connected for a longer time.

RE: J-Link from nRF52840-dk takes several minutes to come up when not connected for a longer time.

MarkusK — Tue, 15 Feb 2022 02:26:14 GMT

Hi Kenneth,

I've tried holding a 10KOhm resistor between ground and TP33 and it seems to work. Unfortunately, replacing the resistor R88 with my equipment is not possible without risk due to the small form factor. So probably I will stay with the jumper bridge from VIO_REF to GND or just plug in the board and have a coffee until it's fully loaded.

Thx a lot for the help.

Regards
Markus

RE: J-Link from nRF52840-dk takes several minutes to come up when not connected for a longer time.

Kenneth — Mon, 14 Feb 2022 17:15:08 GMT

Hi Makus,

Please ground VIO_REF for development, we suspect that the pull-down (R88) is a bit too weak, since it is 10Mohm. We will improve this for future revisions of the DK.

Best regards,
Kenneth

RE: J-Link from nRF52840-dk takes several minutes to come up when not connected for a longer time.

MarkusK — Sat, 12 Feb 2022 03:08:07 GMT

Hi,

nothing looks unusual around the power switch and also not on the source select switch. If I ground VIO_REF everything is working fine. Led is lightning, voltage is 3V. But when I remove the jumper cable, the voltage goes directly down again and starts slowly charging up the VDD until 3V.

Regards
Markus

RE: J-Link from nRF52840-dk takes several minutes to come up when not connected for a longer time.

Kenneth — Fri, 11 Feb 2022 11:54:18 GMT

Hi,

Thanks for the detailed measurements. Can you just do some "investigation" around the Power switch on the DK? Maybe short-circuit it, just to check it may be somewhat broken?

Edit: Can you try to ground VIO_REF on P20?

Thanks,
Kenneth

RE: J-Link from nRF52840-dk takes several minutes to come up when not connected for a longer time.

MarkusK — Fri, 11 Feb 2022 02:01:50 GMT

Hi Kenneth,

- If you are using a USB hub, try to connect the DK directly to the USB port on the PC instead.
Already done. No changes. I tried with USB3.0-Hub and USB2.0 and USB3.0 Ports directly.

- Make sure you have a USB cable with data lines and/or there are no damage to the USB cables.
Already tried different USB-cable.

- Also try a different PC if you haven't already.
Same behaviour on my laptop

- Do you have the possibility to add a oscilloscope/voltmeter to measure VDD when USB is applied? Just to see there is no mechnical issue with the USB and/or Power switch?
I unplugged the boards overnight, then I used a voltmeter and the VDD started at 0,8V and slowly raises to 3V like there is something charged like a capacitor or a battery.
The worst board:
after 1 minute 1V,
after 2 minutes 1.2V,
after 3 minutes 1.3V,
after 4 minutes 1.4V,
after 5 minutes 1.5V,
after 7 minutes 1.6V,
after 10 minutes 1.75V,
after 12 minutes 1.85V,
after 14 minutes 1.93V,
after 15 minutes 2V, Led starts to glow dimly,
after 17 minutes 2.2V,
after 19 minutes 2.4V,
after 21 minutes 2.6V,
after 23 minutes 2.7V,
after 25 minutes 2.8V,
after 27 minutes 3V

The second board goes much faster:
Starts with 1.1V,
after 1 minutes 2V,
after 1.5 minutes 2.6V,
after 2 minutes 3V

Regards
Markus

RE: J-Link from nRF52840-dk takes several minutes to come up when not connected for a longer time.

Kenneth — Thu, 10 Feb 2022 12:20:02 GMT

Hi,

A few questions:

- If you are using a USB hub, try to connect the DK directly to the USB port on the PC instead.
- Make sure you have a USB cable with data lines and/or there are no damage to the USB cables.
- Also try a different PC if you haven't already.
- Do you have the possibility to add a oscilloscope/voltmeter to measure VDD when USB is applied? Just to see there is no mechnical issue with the USB and/or Power switch?

Best regards,
Kenneth