nRF54L15-DK Power measurement with an ammeter.

[br_adams_01]

Hello.

I am reading up on documentation regarding measuring current on the nRF54L15-DK with an ammeter. I do notice that when we set up the board, we need to use the 2x5 SWD header to toggle an analog switch to disconnect the debugger from the nRF54L5. We know what connector we need, but do we need any special dongle/software to accomplish this step? Is there a simpler way to measure the current at P6?

Thanks!

[Hung Bui]

Hi Brandon, 
Could you elaborate more on this "we need to use the 2x5 SWD header to toggle an analog switch to disconnect the debugger from the nRF54L5." ? 

I'm not aware of that requirement. What happens when you just measure the current consumption on P6 by removing the jumper and connect the ammeter there ? 

[br_adams_01]

Hung,

We do get current when we measure on P6, but it was more current than we were expecting from an idle current standpoint. At first, we thought it may have been because the debugger itself was the culprit of the current draw. However, 95% of that current draw appeared to be because peripheral node uart20 was enabled for logging. Turning this off fixed the current draw and is more in line with what the idle current should be based on the Online PPK. We just want to make sure what we are measuring on P6 is actually accurate and we do not need to break the connection between the debugger and the 54L15 via P15.

[Manieldyers]

Hi Hung,

In Nordic's documentation for setting up development kits there are usually instructions on how to prepare the dev kit for low power measurements, ex: https://docs.nordicsemi.com/bundle/ug_nrf52832_dk/page/UG/dk/prepare_board.html for the nRF52-DK.

In the nRF54L15-DK documentation https://docs.nordicsemi.com/bundle/ug_nrf54l15_dk/page/UG/nRF54L15_DK/measurements/set_up_dk.html
It mentions "Use the analog switch on the Serial Wire Debug (SWD) interface that can disconnect the programming interface connections between the debugger and the nRF54L15."

The SWD interface appears to be tied into header P15.
Do we need to connect to P15 to disconnect the programming interface using SWD?
How do we go about using that analog switch?

[Hung Bui]

Hi Daniel, 
The P6 port only has the current flow to the nRF54L chip, not the interface chip. 
The reason you see the recommendation to disconnect the UART and SWD interface using analog switches is that if we want to measure the most accurate current consumption we should disconnect any connection to the interface chip (the debugger) to avoid any leak. 
To disable the interfaces, you can just use the Board Configurator tool in NRF Connect Desktop. The analog switches are controlled by the interface chip as shown here: 

Note: we are having an issue with the latest version of Board Configurator. You may want to use v0.3.7 if you want to disconnect SWD interface. 

[Manieldyers]

I see, so we only need to disable those in the board configurator, or presumably we could do the same in a .conf file. So we don't need to actually physically interact with any connectors to do this.

[Hung Bui]

Hi Daniel, 
Yes you only need to do that via the Board Configurator application. You don't need to do anything physically except for removing the jumper on P6. 

No .conf file won't be able to do disconnect SWD interface or the physical connection to the UART pins.