Max #Connections - BlueNRG-LP (STEVAL-IDB011V1)

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I am a bit confused about the number of connections the BlueNRG-LP can handle.

The device is advertised with 128 concurrent links.

I visited a ST talk where the discussed number was about 50 Connections.

I used the BlueNRG-LP 1.0.0 Radio Wizard that limits the 'Links Number' to 24.

I used the BlueNRG GUI 4.0.0 that limits the 'Num of Links' for the GUI and Python API to 8.

What is meant by concurrent links?

Concurrent 1 = Connections can be open simultaneous, but conflicting if the radio has to handle multiple packet at one moment. (retransmission)

Concurrent 2 = Fully independed channels, working line #n transceivers

Concurrent 3 = The device can store information about this number of connections. But the number of devices with an open connection may be much smaller.

Of course the number of supported links will vary depending on the circumstances.

But could you help me to get a little clearer about this?

My BlueNRG-LP in central role has to bond and connect to 50 peripheral devices.

These 50 connected devices will send ~1 notification per second to the central BlueNRG-LP.

Which APIs can I use here?

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@ST @Winfred LU​ 

Anybody out there who can tell me the maximum of concurrent connections the BlueNRG-LP can handle?

[Winfred LU · Accepted solution]

The radio controller (HW) is capable of supporting 128 links.

But the actual number is linked to the available memory footprint.

A realistic limit today in BlueNRG-LP, with 64 KB RAM, is around 50 connections.

BLE_MultipleConnections in DK 1.0.0 provides an example of 8 connections.

Our stack team is still working on a beta release with improved stability to have huge number of connections.

Please contact your local technical supporting engineers.

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Thank you for your clear response. This clearly helps me!

Is it possible to participate in the beta?

Right now I hit the limit of 24 connected devices. If I choose a setting that would allow me to connect to more devices, I get a runtime error. “Invalid Config�?

Would be awesome to perform some experiments.

[ARamí.1]

Hello, @FWitt.1nfeld​ ​ @Winfred LU​ 

I have read that you say about concurrent connection in BlueNRG-LP.

Could you tell me, how many concurrent connections have you achieved?

I made 2 firmware based on BLE_MultipleConnections example and BLE_SensorDemo_Central example. I get the same result with both firmware. I only can connect 7 of my own sensors.

I configured Num_Link = 15 and NUM_OF_CONCURRENT_GATT_CLIENT_PROC_CONF = 15 in stack_user_cfg

I am not sure if the problem is RAM, the result of Keil are as follows  

Program Size: Code=106280 RO-data=2032 RW-data=1136 ZI-data=36380 ^

I guess the RAM = 56256 + 1396 = 57652 around 58KB

I have 4 service in my sensor.

Service 1{

Chararacteristic1: READ/NOTIFY (5seg) 2bytes

Chararacteristic2: READ/NOTIFY (5seg) 2bytes

Chararacteristic3: NOTIFY 1bytes (1 time in connection)

}

Service 2 {

Chararacteristic1: READ 8bytes

Chararacteristic2: READ 2bytes

Chararacteristic3: READ 2bytes

}

Service 3{

Chararacteristic1: READ 4bytes

}

And OTA Service

Have you been able to connect more than 7 sensors simultaneously?

Thanks,

Best regards.

[Winfred LU]

The currently released stack (v3.1a) was tested concurrent active links up to 24.