What is the maximum number of slaves in BLE star topology

[Abdullah]

As far as I know there is a restriction in older bluetooth versions for number of slaves in a star network. 6 slaves can access same master, totally 7 units in a star topology. Does the same restriction apply to BLE? Can we have (or implement) more than 7 slaves (such as 20) in a BLE star network? Briefly, I want to broadcast some small data from 20 slaves to a master, and I want to know if this is possible in BLE.

[Ole Morten]

When receiving advertisements, there isn't any limitation in the specification as such on how many devices you can receive advertisements from.

At some point in time, the advertising devices will however consume all the time on-air, meaning that there will not be room for any more advertisements packets, but the number of devices triggering this will be extremely dependent on advertising intervals and amount of data in the packets. In general, the number of devices will however be very high.

For completeness, the specification limits a Peripheral device to be connected to only one Central at a time. It does however not set any limits for the number of devices you can be connected to as a Central, but this will most often be limited by the implementation. Currently, we don't have any Central softdevice.

[Ole Morten]

The S120 softdevice, which is a Central capable of 8 concurrent links, plus scanning, is now available for everyone with an nRF51822 kit of some kind, on the download tab of this page: https://www.nordicsemi.com/eng/Products/Bluetooth-R-low-energy/nRF51822/(language)/eng-GB