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

[MarkusK]

Hello,

I have 2 nRF52840-dk developer boards. I'm having a strange and somewhat annoying behavior with the boards. If I haven't connected the boards for a few hours to the usb-port, the boards don't react for a while. The green led on the J-Link (ATSAM3U2CA) does not come on either. After a few minutes it usually works again. The green Led slowly fades in. Sometimes it takes more than 10 minutes, depending a bit on how long they were not connected. If I try to use them during the Led is still not bright lightning SES for example try to reflash the firmware for the chip. As long the Led is not lightning at all SES also doesn't recognize the boards. Bootloader mode is then also not working. If I wait long enough the boards work as normal. Also disconnecting and reconecting with the USB port works directly again.
I already had the device in bootloader mode and reflash the firmware J-Link OB-SAM3U128-V2-NordicSemi 170724 on it. That didn't help. I have the same problem with both my developer boards. I live in Bali and it was difficult to get the boards here. Maybe it's because of the higher humidity, but it's a bit annoying and I'm also concerned that the boards will eventually give up. And since I use the boards to make online projects with students this would not be the best situation. Is this behavior known and is there something I can do about it?

Kind regards
Markus

[Kenneth]

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

[MarkusK]

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

[Kenneth]

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