Central device (nRF connect application) Multiple connections with peripheral devices (nRF52)

[punit]

Hi,
I have 8 peripheral devices each one has at least one sensor attached to it( peripheral will be nRF52xx), the sensor has a sampling period of 8ms. I will be using android application (NRF connect) as a Central to connect to each peripheral devices for accessing sensor data
1) is it possible for a central device to connect to 8 peripheral devices simultaneously?
2) is it possible to receive sensor data from each peripheral at the same time?

[awneil]

punit said:

1) is it possible for a central device to connect to 8 peripheral devices simultaneously

 See the SoftDevice specification for the particular SoftDevice you are using.

Many can support 20 simultaneous connections

punit said:

2) is it possible to receive sensor data from each peripheral at the same time

https://devzone.nordicsemi.com/f/nordic-q-a/52257/how-a-central-ble-device-can-read-data-from-multiple-ble-devices-simultaneously/210239#210239

[punit]

Thank you for the reply, 

I have some more query as follows:

1. The sampling period of each sensor is 8ms, so after each 8ms new data will be available to transfer,I want this data i.e data from all sensor to be updated after each 8ms . is it possible for me to send data from 8 peripheral devices to central device within 8 ms ?. In the below link, it is mentioned that the minimum connection interval is 7.5ms.

https://devzone.nordicsemi.com/f/nordic-q-a/24013/minimum-connection-interval 

Is it possible to send the data in every 1ms/8ms?

2. If I connect 8 peripheral devices, then the connection with all the devices will be stable? the connection will not get lost if the device are ideal?

3. Is there any dependency on mobile/Tablet devices in case of multiple connections?

Regards,

Punit.

[awneil]

An important thing to remember is that "BLE" = Bluetooth Low Energy.

So the key design consideration of BLE is Low Energy - it is not designed for high-speed nor high-volume data!

Yes, the minimum BLE Connection Interval specified by the BT SIG is 7.5 ms.

But note that most phones/tablets will not give you that!

I'm not sure (never tried it) how the Nordic SoftDevices handle this over multiple simultaneous links - eg, whether it can do 7.5ms on each link, or if it's 7.5ms aggregate across all links.

Have you checked in the SoftDevice documentation?

punit said:

the connection will not get lost if the device are ideal

Not sure what you mean by that?

It is in the very nature of any & all radio links that connections can always drop out.

punit said:

Is there any dependency on mobile/Tablet devices in case of multiple connections

You would have to RTFM for the device(s) in question.