max number of broadcasters scanned from a central device

[daveln]

Hi,

I'm using nrf51822 with s110 softdevice v6

My question is the following. How many devices sending advertising messages can be detected at a time by a central unit(pca10000 or pca10004)?

The specs gives information about BLE topology (star), or maximum number of active devices connected to a master (limitless, when on previous versions of BT, the maximum where 7), but they dont give information about the maximum number of devices that a master can scan & get advertising messages at a time.

[daveln]

Regarding advertisements, theoretically there is no limit in BLE. What happens in practice is that, since i have only 3 advertising channels, a lot of BLE devices advertising themselves at same time will result in collisions. So I think the max advertisers in a single ADV / SCAN interval was limited.

Any idea of avoiding collisions?

[John]

The following quote comes from the 4.1 Bluetooth specification Volume 1, Section 3.3.2.2 Advertising Broadcast channel:

"The channel is divided intoadvertising events where each advertising event can hop on all three advertising PHY channels. Consecutive advertising events begin on the first advertising PHY channel. The advertising events occur at regular intervals which are slightly modified with a random delay to aid in interference avoidance."

And should address your concern.