nrf52840 not entering lower power mode, using development kit with sample BLE application

RE: nrf52840 not entering lower power mode, using development kit with sample BLE application

Jerry Patrick Morrow — Wed, 23 Mar 2022 14:37:03 GMT

Hello,

Thanks so much! I'm seeing below 2 microamps now during sleep. If you think I can get it lower, please advise.

I added these lines in the prj.conf file. There were some warnings during the cmake config of Zephyr because the UART/serial was not available, but it still was able to build.

Next on the list is setting up the connection interval to 4000 msec (maximum allowed). I was able to do this with the nRF Connect tool before, but now that i'm running 'stand alone' (no serial/usb), I want to configure in the build somehow. Right now average current during connection is still too high, and not close to what the online power profiler said that could be achieved. I'm looking for < 10 microamps average.

RE: nrf52840 not entering lower power mode, using development kit with sample BLE application

Stian Røed Hafskjold — Tue, 22 Mar 2022 12:29:57 GMT

Hi, if you connect the PPK to the external supply header, the measurements will include the current to the whole DK, including the debugger chip, some analog switches, LEDs, etc.

So what you have to do is to set SW10 (Vext -> nRF) to the ON position and SW6 to nRF only. Now the external supply header is isolated from the rest of the DK, powering only the nRF52. Next step is to connect the USB cable (to J2), because you need to power the debugger, otherwise there will be leakage currents going from the nRF52 to the debugger chip, through the SWD and RESET lines.

The software running should be low power by default, so it should be enough to use k_sleep() forcing the CPU to idle mode. There can be active peripherals however, like the UART, as you mention, but I think you have to use CONFIG_SERIAL=n to actually turn off the UART as well, not just the console.

Best regards,
Stian

RE: nrf52840 not entering lower power mode, using development kit with sample BLE application

Jerry Patrick Morrow — Mon, 21 Mar 2022 22:33:18 GMT

I did find if i set the SW6 toggle switch to 'nRF ONLY', the baseline current goes down to 500 microamps. That's much better, but the SoC is still not in low power mode.