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nRF52840 BLE power profiling

Sridhar Jonnavittula

Hi,

1. After studying about power profiling and application examples/ble_peripheral/ble_app_pwr_profiling, came to know that this example currently supports advertising and peripheral connection profiles. Is it like it wont support scanner and central connection profiles?

2. Can I use Ampere-meter for accurate readings?

3. If I want to use existing profiles with Ampere-meter, is the procedure : prepare the DK, program the application, connect Ampere-meter, run application, observe the values correct?

4. https://devzone.nordicsemi.com/b/blog/posts/nrf52-online-power-profiler link specifies DCDC enable and low frequency 32khz clock but example did not give. Do we need to add these two functions and test?

5. Can I set other PHYs and verify numbers? If yes how to excite it?

Please clarify doubts.

Thanks

  • +1

    Hi,

    1. The Power profiling example only support advertising and peripheral connection. However, you can take another central example from the SDK and adapt it to be power friendly before measuring. The most important things to do in order to reduce power consumption is:
      1. Disable logging
      2. Disable any LEDs
      3. Build a release build
      4. Enable the DC/DC if you have it your your HW (not enabled by default in SDK examples)
    2. Yes, but it may not give accurate results. The current consumption varies significantly even in idle state (due to the LDO refresh mode). Please see the Measuring current section in the documentation for your DK.
    3. No. The current consumption will vary over time, depending on what the device is doing. I do not trust that an ampere meter will give you correct average measurements, unless the device is in a fixed state for a long time (e.g. system OFF, or eternal loop in system ON with no BLE activity, calibration etc.). I recommend measuring distinct states/events separately so that you can view the current consumption "waveform", for example measuring the voltage drop over a series resistor using an oscilloscope.
    4. The Power Profiling Application has the 32 kHz clock running at all times (except in system OFF, where that is impossible). All BLE examples keep the 32 kHz clock running as that is enforced by the SoftDevice. The DC/DC is not enabled, but you can do that yourself using sd_power_dcdc_mode_set().
    5. Yes, you can measure using different PHY's. Again, I recommend taking a suitable example and just doing the minor modifications suggested in the first point, optimizing the example for current consumption before measuring.

    Please note that the product specification include typical current consumption numbers for most scenarios allready. Also note that current consumption measurements of a BLE device is quite complex, so if your measurement result deviates significantly from this, then it is more likely to be a issue with how you measure than with the nRF itself.

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