Power Consumption - Scanning and Advertising at same time - S140

[Pegaze]

Hi,

I'm working on a project using BLE via s140, everything works fine until I look more seriously at the current draw of the device.

Simply, my project starts a Scan which lasts X milliseconds and which repeats every 20seconds. In parallel, the device advertises at interval Y milliseconds.

I use Power Profiler in order to obtain average consumption values and here are the results for different configurations.

(Note : Scan_Interval = 100ms and Scan_window = 50ms)

Scan duration  = 1s / Adv Interval = 100ms

So we have:

• Average = 273,31uA
• Scan + Adv = 2,44mA
• Adv = 134,93uA

Scan duration  = 1s / Adv Interval = 3s

So we have:

• Average = 293,99uA
• Scan + Adv = 5,74mA
• Adv = 11,78uA

My question is therefore: why when I increase the advertising interval, during Scan + Advertising, I get a significantly higher consumption ?

thanks for your support

[Simonr]

Hi again

You say that your scan duration is set to 1 second, but the NRF_BLE_SCAN_SCAN_DURATION seems to be set to 0 (looping forever) in your sdk_config.h file (that shouldn't be the issue though, but more for your information). I think it would be better to change this define to 1 second instead of using the ble_cus_scanconfig_update() function you made yourself. Did you disable advertising altogether for your "Only Scan" power profiler trace, because it seems almost identical to the 3s adv interval trace? Please make sure you disable/remove all mentions of advertising (both init, start, uninit, and so on).

Best regards,

Simon

[Pegaze]

Hi,

Indeed, the default scan configuration is 0 (looping forever) but as you noted, I use the ble_cus_scanconfig_update() function to change it to 1s. To avoid any problem related to my application code, I therefore used the following configuration during my tests:

Yes, I correctly removed all traces of advertising during my "OnlyScan" test, I even checked on the nRF Connect app that my device was no longer visible.

Knowing that scan lasts 1s and that advertising is configured at 3s interval. I just think that on the "Scan + Adv 3s Interval" scheme, we fall between two advertisements, which explains the similarities with the "OnlyScan" scheme.

[Simonr]

Okay, it still seems like the scanning in these two plots are scanning with a 100% duty cycle (scanning continuously). Can you try reading out the duty cycle (scan window) value when only scanning, as it doesn't seem to be set to 50ms. It only seems to be the advertisements in the 100ms that actually stops the scanning every 100ms, so something seems to be wrong with the duty cycle when the advertiser doesn't run. Do you see the same if you modify a pure central application as well (for example the Nordic UART service Client)?

Best regards,

Simon

[Pegaze]

Hi,

So I used the example you mention and here are my results:

• On my custom board
  • default configuration

• • custom configuration

• PCA10056
  • default configuration

• • custom configuration