nRF52832 high current with __WFE();

[Rick]

While analyzing the current consumption of my nRF52832 Dev Kit I noticed that the system on low power current was significantly higher than expected. To further investigate this I loaded a small program that only has a call to __WFE() in a while loop. Using a multimeter in series with a 3V power supply connected to P21 I measure about 235µA. My board has a 10ohm resistor on R6 and SB9 cut to allow current measurement with an oscilloscope but it's not accurate enough to measure these low currents hence the multimeter.

What causes the current consumption to be higher than the 1.9µA (plus some for RAM retention) in the datasheet? For what it's worth I'm on SDK 13.

Edit: Configuring the 4 leds and turning them off reduced the current to about 17µA. Configuring the buttons doesn't make a difference, it only raises the current when pressed.

[Turbo J]

Did you connect the power only to P0.21? That would be very wrong.

[Rick]

P21 is the external power header, P0.21 is a GPIO port. Powering it through the GPIO would be very wrong indeed :)

[Sigurd]

Hi,

You need to measure on P22. When you measure on P21 you are also measuring the current used by the SEGGER programmer/debugger. See this infocenter page on how to measure with a ampere-meter.

If you are interesting in current measuring for low-power applications, I would recommend buying the Power Profiler Kit. You can read more about it at the product page, and in this blog post.

[Rick]

Thanks, now I measure about 1.3uA. I thought the debugger wouldn't use any current when it's off but I guess I was wrong. The power profiler would be really cool to have, but as an intern I think it's a bit out of the scope of my project and budget :)