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About BLE connection (between a master device and many slave device)

Youngho Oh
Prodigy 40 points
Other Parts Discussed in Thread: CC2540, CC2564

hi~

 I have been studying about BLE.  I have some question about BLE.

A master Bluetooth BE/EDR device can communicate with a maximum of seven devices. unlike a master BE/EDR device, master BLE device is not defined. (http://en.wikipedia.org/wiki/Bluetooth_low_energy)

 I thought that a master BLE device can communicate with ten devices. so I made code considering 'SimpleBLECentral' sample project and run.

 I can connect to three devices

 but I get the error(bleNoResources : 0x15)  when I  try to establish a new connection to a fourth device. 

 why occur this error???

 Can I connect a master to ten other device?

 if possible, How can I do?

 help me.... 

  • 0
    TI__Expert 4060 points

    Hi Youngho,

    The Bluetooth 4.0 spec doesn't set any constraints or limits on how many slaves a BLE master can be connected to, unlike BR/EDR. However, in a real implementation, every connection takes up a certain amount of memory and processing power. Our CC2540/41 is limited to 3 simultaneous connections because of this. There many be other devices that can support more, I think the CC2564 can connect to up to 8 devices at once.

    Another alternative is to open and close connections dynamically, which can be practical because BLE connections are much faster to open and close than in BR/EDR.

    Best regards,

    Karl

  • 0 in reply to Karl T.
    Prodigy 40 points

     Thanks Karl :)

     I have another question to you 

     Is connection limit set by BLE stack???

     Does BLE stack which support MCU which process better than 8051 exist ???

  • 0 in reply to Karl T.
    Prodigy 50 points

    Could you please elaborate on a method of incorporating a dynamic system like this?

    How could the master be setup? Would it automatically disconnect the oldest connection when it detects three slaves? Or could this happen when it detects a fourth slave trying to connect? 

    I would like to implement this but keep devices connected unless the master senses another slave is trying to connect and it is at capacity. 

    Thanks!

  • 0
    Prodigy 50 points

    In BLE, each connection between a master and a slave is identified by a 32-bit access address. This is 2 raised 32 connection and the Bluetooth 4.0 specification does not impose further limits on the number of slaves that can be connected to a master. However, there are practical limits on that number, depending on the type of communication between master and slave, on the connInterval parameter setting and the BER that can be assumed.  The lower the connInterval the more will be the demand of energy on the network and lesser the no of slaves. Maximum slaves will be in higher connInterval (4s) parameters upto 5000+, though the connInterval is also a function of the use case. If the master is a device without constraints of power and memory it could have the theoritical max, this is unlikely to be case of most field devices which have shared antennas with wifi and blue tooth classic.