Low Power Blinky Example - Power Consumption Problem - Power Profiler Kit II and nRF52840 DK

[thiago_hd]

Hello,

I have tried running Blinky example with some Low Power directives in the code without success. I came here for help then.

The current consumption used by the example, based on the Blinky sample, on the nRF52840 DK, stays around 2mA when the LED is off.

I am using NCS v2.1.0 and nRF52840 DK. I have used the Voltage Source meter mode for consumption measurement on the PPK II. 

Here is the code:

4276.blinky.rar

Though the USB cable is connected to the DK in the image below, it is disconnected from the PC USB.

[Hieu]

Hi thiago_hd,

I just want to know that I have received your ticket. Due to a backlog situation, I will need some time before I can follow-up with you. My apology for the inconvenience.

Hieu

[thiago_hd]

Hello Hieu 

When can I expect an answer?

[Hieu]

Hi thiago_hd,

Sorry for the long wait.

I think what you perceive to be not working is that you find 2mA is way too much when the LED is off?

As you are not powering the board with the USB cable, the PPK is powering the entire board. Therefore, the 2mA you see is the total consumption of the board, not just the nRF chip.

If you put the USB cable in, you will see only the current drawn by the nRF DUT. Then you can see that the device running your source code is drawing very little current. Only about 15.74 uA.

Sorry again for the long wait.

Best regards,

Hieu

[thiago_hd]

Hello Hieu 

Could you explain for me in a drawing how am I supposed to connect PPK to the nRF USB connector in the nRF52840DK?

I am not sure how I connect PPK this way.

[Hieu]

Hi thiago_hd,

I think you have misunderstood me. I am talking about the same USB port on the DK's short edge as the one you are using.

Your setup as in the picture is already fine, just connect the USB cable to a power source/PC. 

Best regards,

Hieu

[thiago_hd]

Hieu it doesnt make any sense to me to plug two power sources (USB and PPK) at the same time. Let me tell you what is the setup that I have.

I plugged PPK's Vout and GND pins in the P21 External Supply connector + and - pins, respectively.

I have the USB plugged (and powered, since you requested it) on J2 USB Connector (the same port we use for debugging/flashing).

P22 (nRF current measurement) is short circuited

SW8 (Power) switch is ON.

SW10 (Vext -> nRF) is OFF.

SW9 (nRF Power Source) is set to VDD (instead of Li-Po and USB).

SW6 (nRF ONLY | DEFAULT) is set to DEFAULT.

SW7 (TRACE) is set to Default.

This is what is happening now:

[thiago_hd]

Hieu it doesnt make any sense to me to plug two power sources (USB and PPK) at the same time. Let me tell you what is the setup that I have.

I plugged PPK's Vout and GND pins in the P21 External Supply connector + and - pins, respectively.

I have the USB plugged (and powered, since you requested it) on J2 USB Connector (the same port we use for debugging/flashing).

P22 (nRF current measurement) is short circuited

SW8 (Power) switch is ON.

SW10 (Vext -> nRF) is OFF.

SW9 (nRF Power Source) is set to VDD (instead of Li-Po and USB).

SW6 (nRF ONLY | DEFAULT) is set to DEFAULT.

SW7 (TRACE) is set to Default.

This is what is happening now:

[Hieu]

Hi thiago_hd ,

thiago_hd said:

it doesnt make any sense to me to plug two power sources (USB and PPK) at the same time.

Yes, I agree that it does not make much immediate sense why the measurement is only valid when you plug in the debugger cable.
I tried to dive into the schematic to show you how it would work, but was not very successful due to my limited HW expertise. If you wish to fully understand the details, please let me know and I will try to pull in more knowledgeable people.

But in any case, the J2 USB Connector has to be plugged in. I found an official source here: https://infocenter.nordicsemi.com/topic/ug_ppk2/UG/ppk/measure_current_source_meter.html
The picture is small, but you can open it on a separate tab and zoom in to read the details.
The source also points out one thing both you and I did wrong. PPK2-VOUT has to connect to nRF52840 DK P22 pin VDD_nRF (the pin would be the upper one in your picture.

thiago_hd said:

This is what is happening now:

Unfortunately, I cannot reproduce this. Are you opening any VCOM maybe? What is your USB cable plugging into?

---

Below is what I see in my setup yesterday and today:

Yesterday setup, same as your original one, with J2 plugged in:

Today setup, as instructed by the guide linked above

Finally, here is my setup today

USB plugged on J2 USB Connector

P22-VDD_nRF (see picture) connected to PPK2-VOUT

P21-Ground connected to PPK2-Ground

SW8 (Power) switch is ON.

SW10 (Vext -> nRF) is OFF.

SW9 (nRF Power Source) is set to VDD (instead of Li-Po and USB).

SW6 (nRF ONLY | DEFAULT) is set to DEFAULT.

SW7 (TRACE) is set to Default.

[thiago_hd]

Hello Hieu I got to reproduce your results.

However, there is one thing I had to do.

I had to open the SB40 short circuit (R90).

Then I got this result:

Can you explain to me why I can only see the turn ON/OFF event of the LED, instead of it's current consumption during the time that the LED is ON? Is it because the current draw for the LED is coming from the USB port? Is there a way to change this so the LED will be fed by the PPK2?

How can I reduce the current consumption even more? I wanted to achieve as little as 5 uA on average, during the time where everything is SUSPENDED.

[thiago_hd]

Hieu any suggestion?

[Hieu]

Hi thiago_hd,

First, sorry I forgot to mention the SB40 setup. Since we are working on Power Profiling, I assume it is done already. That was a bad assumption.

thiago_hd said:

Can you explain to me why I can only see the turn ON/OFF event of the LED, instead of it's current consumption during the time that the LED is ON? Is it because the current draw for the LED is coming from the USB port?

Yes, you are exactly right about that. The setup only measures the current drawn by the nRF chip.

thiago_hd said:

Is there a way to change this so the LED will be fed by the PPK2?

On this note, are you going to have your custom board with only the nRF and an LED or are you going to use the DK as a temporary solution?

If you are using the DK as a temporary solution, then the setup we initially started with will measure exactly that. Just revert to it, remove the debugger USB, short the P22 pins together with a jumper to replace the broken SB40.

If you are having your custom board but would like to evaluate with the DK, I will need to check with someone experienced before I answer you. I will get to this on Monday.

Alternatively, the setup right now (described in our last replies) measures only the nRF chip. If your final product consisted of only the nRF chip and an LED, you could calculate the expected consumption of your LED and add to the current measurement of the nRF chip.

thiago_hd said:

How can I reduce the current consumption even more? I wanted to achieve as little as 5 uA on average, during the time where everything is SUSPENDED.

There are a few resources I can recommend for you:

The following blog post discusses how to do it on nRF52 chips. Some points are detailed for the nRF5 SDK, but can be transferred over to nRF Connect SDK, or is covered in the next article.
Optimizing Power on nRF52 Designs

The following blog post discusses how to do it on nRF53 chips. Again, the points can be transferred over to the nRF52840 development.
Optimizing Power on nRF5340 SoC Designs

I think you will also use some wireless communication when you use Nordic Semi's products. If you use BLE, the Online Power Profiler tool is helpful to estimate current consumption changes as you tweak BLE parameters. It can be found here:  opp 

Here is the official guide on the nRF Connect SDK documentation. I think the blog posts above already included all ideas in this document though. Power optimization — nRF Connect SDK documentation

Finally, the entirety of DevZone is a resource. If you want to optimize some specific use case, just search and there might have been someone else who did it. This Q&A is a good example:  nrf52 - PPI + EasyDMA Power Consumption  

I feel a sense of urgency in your comments. Is there an urgent topic going on? I am unfortunately back in another backlog situation. It is difficult, but if something is urgent, please let me know and we will see what can be arranged.

Best regards,

Hieu

[Hieu]

Hi thiago_hd,

Sorry I got the information yesterday but forgot to type it here.

thiago_hd said:

Is there a way to change this so the LED will be fed by the PPK2?

There is no way to power only the nRF and the LED, and the only option covering the LED is powering the entire board.
You will always see some quiescent current drawn by components other than the LED and the nRF chip. A big power consumer in this case would be the debugger chip.

Best regard,

Hieu