Query regarding Central and peripheral || Advertisement

[Rakesh R]

Hi All,

I am new to BLE technology and I am working on nRF52840 and I have below queries.

1) I need to operate my device to scan and advertise both at the same time when it is already connected to the phone.

Is it possible?

2) While scanning how may devices I can scan if all are advertising at the same advertisement interval, Is there any chance of packet loss if we have around 100 devices to scan?

- Advertising interval maybe around 2 seconds

3)  can I send 2  advertisement packets with different power?

4) Is there a way to find a range of devices with 1/2 feet of accuracy? RSSI is not a good option, right?

[Dmitry]

Hi,

1) yes, you can configure a broadcaster and an observer along with a connection.

2) there is always a chance of packet loss, even when scanning a single device, there are too many devices at 2.4Ghz band causing interference. Also, more devices are on air, more chances for collisions. In your case, assuming 100 devices are advertising with 2-second interval and payload is 31 bytes (whole packet takes about 400us on-air time), one can expect about 2% chance of collision, that is quite good.

3) you can change TX power with sd_ble_gap_tx_power_set() API call (I can't say for sure whether you can change TX power on the fly, maybe you will need to restart advertising to change power).

4) is AoA/AoD positioning an option for you?

[Rakesh R]

Hi Dmitry,

Thanks for the reply.

1) Can I have two different advertisement packets with two different power??? Power will be fixed for each advertisement packet.

[Dmitry]

Rakesh R said:

Can I have two different advertisement packets with two different power??? Power will be fixed for each advertisement packet.

You can dynamically change the content of advertising packet, switching between them, see here. Concerning different power - as I answered above, there is an API to change advertising power, though I didn't try to change it on the fly, maybe you will have a luck.

[Rakesh R]

Hi Dmitry,

for the prompt response.

I got your point here for transmission power of advertising packet, but it still seems some confusion.

let me ask it again.

i need to find the device in particular range, there is two categories of range let's say one is up to 8 feet and other is 8-20 feet,.

so now i will have device which will advertise two advertisement packets, one with low power and one with high power.

so power will be fixed initially, no need to change power dynamically.

so both advertisement packets will have there own configuration.

[Dmitry]

You cannot have two sets of advertisements with different parameters working in parallel. The only way is to switch between "low power" and "high power" packets dynamically.

[Rakesh R]

Okay got it, thanks for the answer.