How might scanner influence peripheral power consumption?

[Dmitry]

Hi!

We are developing a beacon for a hursh environment based on NRF52832 chip and now close to production. Recently we've noticed that unit power consumption for some reason depends on the number of scanners.

Today I've made small research - took 10 mobile phones, installed on them nRF Connect and run it on each phone. The unit under test was connected to ammeter. Below is the video of how ammeter behaves depending on the number of scanners.

No scanners:

10 scanners:

The question is what causes such a behaviour?

The unit works in scannable and connectable mode since customer has to be able to configure beacon parameters in the field.

I've looked throught some posts and BLE specs and figured out that advertiser listens to the scan requests or/and connection requests after each advertising event on all three channels but still don't uderstand how it could increase system current. BTW, scan response is switched off in the firmware so beacon only sends advertising packets and doesn't answer to scan requests.

--

Regards,

Dmitry.

[Stian Røed Hafskjold]

Even though you turn off scan response in the peripheral, the peripheral still has to listen to every request that comes in, in case there is a connection request. So when you have many scanners, they will send out scan requests, and the number of RX events in the peripheral that receives data increases. When the RX event receives data, the RX is on for a longer time, and the total average current increases.

[Dmitry]

Hi Stian,

Thanks for reply! You've confirmed my thoughts but there is another question - is there any limit the current may reach? The experiments described in the original post resulted in power consumption saturation as the number of scanners grows. I expected this result but just want to know how it works since we have to prove to the customer that battery will work according to the product specification.

[Stian Røed Hafskjold]

Yes, you will reach a limit. That limit will be reached when the scanners are responding to every advertising packet the peripheral sends out.