nrf5340 current consumption of shell by using uart async api

RE: nrf5340 current consumption of shell by using uart async api

whati001 — Thu, 05 Jun 2025 13:31:50 GMT

Hi Vidar,

yes I know. Thank you very much for your help.

Regards,

Andreas

RE: nrf5340 current consumption of shell by using uart async api

Vidar Berg — Thu, 05 Jun 2025 06:18:30 GMT

Hi Andreas,

Yes that is something you can experiment with. It seems like you are aware of this already since you have enabled CONFIG_PM_DEVICE, but note that you can use the Suspend and Resume tasks on the shell device to disable and enable the shell as explained here https://docs.nordicsemi.com/bundle/ncs-latest/page/nrf/test_and_optimize/optimizing/power_general.html#put_the_external_flash_into_sleep_mode_in_inactivity_periods

RE: nrf5340 current consumption of shell by using uart async api

whati001 — Wed, 04 Jun 2025 16:45:58 GMT

Hi Vidar,

no, the device does not have a button. However, the best solution would be to wake up the MCU before UART communication via an ordinary GPIO. Guess, a little bit hacky, we can also use the UART RX pin after suspending the UART to save pins.

Regards,

Andreas

RE: nrf5340 current consumption of shell by using uart async api

Vidar Berg — Tue, 03 Jun 2025 06:22:39 GMT

Hi Andreas,

Correct, the LP driver won't work with non-nordic devices such as the serial bridges you mentioned, unfortunately. Does your device have any buttons, etc that could allow the user to enable the shell only when needed?

Best regards,

Vidar

RE: nrf5340 current consumption of shell by using uart async api

whati001 — Tue, 03 Jun 2025 05:59:13 GMT

Hi Vidar,

thank you very much for your feedback, which helped me to turn my head and understand the problem. I just have one question regarding the promoted `Low power UART driver`, which I guess I already know the answer to. I think this driver is Nordic-specific and not out of the box. Is it available for standard UART to USB bridges like the Silicon Labs CP210x or in the VCP of the JLINK?

Regards

Andreas

RE: nrf5340 current consumption of shell by using uart async api

Vidar Berg — Mon, 02 Jun 2025 12:58:52 GMT

Hi Andreas,

The UART continues to request the HF clock source as long as rx reception is enabled, which results in the increased idle current you measured. The standard HW control signals are not asserted early enough for the HF clock to start up and for the UART to resume receiving data in time. But if you control the UART driver implementation on both sides, you may consider using our Low power UART driver with the custom handshake signals.

Best regards,

Vidar