how to connect 4 Slaves to One Master using BLE

[Umes_fln]

Hi,

I am working on a project where I have 4 sensors. Each sensor transmits(slave & Peripheral) its value using BLE to the Receiver (Central & master) which is also BLE. I am new to the Bluetooth low energy and understand that BLE works very low power however I think BLE only works one to one connection. Wondering if it is possible to have 4 peripheral connected to one central at one time. if so are there any examples. Each slave is trying to send 32bits value of sensor every 250ms. Please help.

[endnode]

You don't mention any specific BLE device so the only possible answer to your very general question is: Yes, BLE enables "star" topology where several peer-to-peer (as you correctly said BT is always only point to point) connections end in single device and that can link them on very top (APP) layer into single use case.

If you ask how to do it or where is example for Nordic nRF5x products then you will need to understand a bit of that "low level" because these are pretty deep embedded systems with certain parts in "lower" stack and corresponding API... however there are such examples in nRF5 SDK which run on nRF5x DK boards out of the box (see examples\ble_central\ble_app_multilink_central project). Good luck!

[Umes_fln]

Thanks for your prompt replay Endnode. So with nRF5x products I can do following?

1. Put all the salves on advertising.
2. the Central scanning
3. The central makes connection with the Slave1 first, then the Slave 2 and so on 4.Read the value of the slave 1, Slave 2 , Slave 3 and Slave 4.
4. Slave 1,2,3,4 go to sleep.
5. after 200ms all salve wakeup and read the value of the Sensor 1, Sensor 2, Sensor 3 and Sensor 4
6. repeating 5 & 6.

Thanks in Advance

[Sigurd]

Hi Umes_fln ,

Yes, the steps you describe is possible to do.

[endnode]

However some steps looks cryptic to me. E.g. if slave goes to "sleep" does it mean that it will drop the link? If yes then how it will wake-up and do something when it must wait for new connection? If no then it's not really "sleep". And probably some more logical flaws. But technically there should be no problem on nRF5x side indeed;)

[Umes_fln]

I mean maybe keeping the slave in low power mode such as shutting its peripheral down but keeping the ble part alive etc.