nRF52DK usb related power consumption issues

RE: nRF52DK usb related power consumption issues

JONATHAN LL — Mon, 11 Jan 2021 13:06:40 GMT

Hi Lee,

Do not have any papers or documents on the why part, but to remove the switching battery\usb source during the development cycle you can use a external debugger on the debug in, that way you can power the device from a coin cell and debug at the same time.

I will update you if i find anything on the why part. But generally the reason the USB is inaccurate/unreliable is due to switching noise from the USB.
Regards,
Jonathan

RE: nRF52DK usb related power consumption issues

essele — Thu, 07 Jan 2021 15:17:57 GMT

Thanks for the reply Jonathan.

I was trying to understand a bit more about "why" ... as it's an absolute nightmare to keep switching between the coin cell and USB power during the development cycle ... and I'm definitely at a stage where I need to try many things to see what the impact on power consumption is.

Ignoring the debugger reset issue, which is easily avoided, it certainly doesn't look "unreliable", it just looks a couple of uA high .. if I understand why, then I can built that into my development cycle without too many concerns.

It does seem like a bit of a crazy limitation for a dev board for this kind of device though, that also (on the surface) makes no sense at all.

Lee.

RE: nRF52DK usb related power consumption issues

JONATHAN LL — Thu, 07 Jan 2021 12:29:29 GMT

Hi Lee,

The number 2.0.0 is the revision\version of the board. PCA10040 is the product and 2020.39 is the production date, year and week number.

But to the current measurement, it is not reliable to measure current on the DK with the USB connected. You can read more about how to correctly set it up on our infocenter.

Summarized in short it is:

Do not use the USB connector to power the DK.
Current measurements is unreliable when a serial terminal is connected to the Virtual COM port.
After programming the device, the USB must be disconnected and the development kit power cycled to reset the debugger chip before current measurement.

The issues you are seeing is related to the debugger chip not being reset properly(Must be power cycled) and the use of USB.

Regards,
Jonathan

RE: nRF52DK usb related power consumption issues

essele — Wed, 06 Jan 2021 21:49:46 GMT

Hi Jonathon,

I'm not sure how I tell what version of the 52dk I have ... it's a couple of days old. The main IC label shows "PCA10040 2.0.0 2020.39".

In the J-Link properties is shows hardware version 1.0.

I don't need to actually do a rebuild ... I can also "connect j-link" followed by "disconnect j-link" and it also sorts itself out.

It's triggered by unplugging the USB or switching off, but not the reset button.

Cheers,

Lee.

RE: nRF52DK usb related power consumption issues

JONATHAN LL — Wed, 06 Jan 2021 14:56:46 GMT

Hi Lee,

[quote user=""]re-"build and run"[/quote]

Do you have to re-build? or is does just re flashing\running again work?

Can you also share witch version of the 52dk you have?

Regards,
Jonathan