Connecting up to 20 slaves to one master

[Bluetoothy]

I am working with a university project where need to connect up to 20 wireless sensors together with 1 master, which will be communicating with either a computer or smartphone. So obviously the master has to be a BLE/WIFI device. But since i want to create a flexible system it could be interesting to make the sensor devices universal, so any unit could become a master or a slave.

I have been looking at nRF51822, but i am not sure if its capable of both being in standard 2.4GHz RF and BLE mode at the same time?

My idea is to connect all 15-30 sensors to the master by traditional RF, and make the master send this data to my PC/smart-device.

All suggestions are welcome, thanks in advance.

[Asbjørn]

I would recommend you to use either proprietary or ANT for collecting information from the other nodes. Since you have the nRF51822 proprietary would be the way to go for now. If you want to use ANT you have to use the nRF51422. It's the same chip, but it's possible to program ANT based softdevices into it. ANT has built in functionality for supporting lots of nodes and would probably be easier to get going compared to proprietary. For proprietary you have more options and more data through, but you have to handle a more if the behavior from your application.

There's a softdevice that handles both BLE and ANT concurrently, it's called S310. For proprietary you can you the S110 softdevice with the timeslot API. This allows you to get access to the radio peripheral for periods of time to do proprietary concurrently. There's an example here. Alternatively is to switch the S110 on and off. This takes a few millisecond and if you don't do BLE communication constantly this might be an option too.

[Bluetoothy]

I was wondering if i am overkilling this project and basically would be able to go with a simple nRF24 and traditional RF?