Power Consumption

[mrezan]

Hi Nordic Expertise,

I'm buying PPK to measure the current. Meanwhile I'm studying to reduce power consumption and I'm using:

a. nrf52840, advertise interval 500ms.
b. 1 button. Active low. Default NC. No external pull up.
c. 1 input. Wire connection. Active low. Default NC. No external pull up.
d. 1 cr2032 battery.

1. If we enable peripherals in "sdk_config.h" but not used it in our application, not even initialize. Is the consumption still same with when disable it?

2. The tx power level in datasheet "-20 to +8 dBm TX power, configurable in 4 dB steps". By right -20dBm should have the lowest tx current right? Do any concern I need to aware if using the lowest one?

3. For input, using toggle interrupt or read the pin status (5s) is used lower current?

4. Is it achievable to run one month before the battery die?

5. let say I change the nrf52840 with nrf52810. The application is same. Do the power consumption will be the same or reduced

6. Using app timer, trigger every 1s compare with trigger every 2s. By right trigger 2s have less power consumption right?

7. This one not related to power consumption. Component in (c) seem not stable when disconnected the input wire. Keep getting toggle event. Is it no other choice then must add pull up resistor? While component in (b) so far stable.

Any advice to reduce the consumption even more is appreciated.

Please help.

Thanks & Best,
Rezan

[Simonr]

Hi Rezan

Are you using an NRF52840 Development kit, custom HW or some third party evaluation kit/module here?

1. If it's not initialized it should not draw any current consumption, but note that configs like logging will initialize and enable some things under the hood, so disable anything you don't use for good measure.

2. Correct, -20 dBm TX will draw the least amount of current, but note that the range of your radio will be affected by lower TX powers, as the signal will be weaker.

3. I'm not sure I understand what you mean by "read the pin status (5s)" here, can you clarify. What are you using the input for exactly?

4. That depends very much on your application. For example, with the radio running constantly (even with -20 dBm TX power) almost certainly not. But if the device is mostly in an ultra low power mode I think that should be doable off a cr2032 battery (see product specification for more details on current consumption scenarios).

5. If you compare the product specifications of the nRF52810 and nRF52840 you can see that the nRF52810 generally less power consuming. This is mainly due to the lack of an FPU in the nRF52810 and the much lower RAM and Flash memory).

6. Triggering every 2 seconds compared to every 1 seconds will indeed draw less power.

7. Yes, I think you should add an external pull resistor. This depends on the component and if they have internal pull-ups/downs etc. But an external one is strongly recommended if you're seeing unexpected toggle events.

Please check out this guide on general advice for optimizing current consumption on the nRF52 series devices, and also make sure to check out our Online Power Profiling tool that helps you test out different current consumption scenarios for BLE events with different parameters and TX powers, etc.

Best regards,

Simon

[mrezan]

Hi Simon,

I'm using custom HW.

Thanks for all the answers and advice.

3. For example as in (b) and (c).
"using toggle interrupt" -> we can create a trigger event as interrupt when the status of the pin changes.
"read the pin status (5s)" -> we can manually read the pin status and the cycle is read every 5 seconds.
Between these two which one uses less current?

Thanks & Best Regards,
Rezan

[Simonr]

Hi Rezan

Question 3. I'm not sure to be honest. How often will you trigger this event in that case? I think you should test both on your end to find out for sure, but I have a suspicion the trigger event as an interrupt will be better.

Best regards,

Simon

[mrezan]

Hi Simon,

How often triggered is hard to tell as it depends on the user. 
Btw thanks for your advice.

Best Regards,
Rezan