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Always connected or always disconnected?

andrei bulucea
Prodigy 10 points
Other Parts Discussed in Thread: CC2540

Dear Karl,

>(usually the phone/PC) sends out periodic beacons at a period called the connection interval, and the slave responds to this beacon if it has data to provide. The connection >interval will usually be between 100 ms and 32 seconds.

1) In a BLE mobile phone (or BLE gateway) scenario will the host AUTOMATICALY connect to all available (and pairable) clients and then keep this link alive? 
In other words, will these connections get formed automatically (without user intervention) or will these connections be initiated only a Phone app (that needs to be launched by an user) will be able to initiate a connection?

Suppose I have an RSSI based application that unlocks a PC screen when my Cell phone gets very close to PC. If connection doesn't not happen automatically, the "RSSI magic" will not work. 

2) What consumes more energy?  (a) Advertising (std packet length) every second or (b) maintaining a connection every second?


-Andrei

 

  • 0
    TI__Expert 4060 points

    Andrei,

    1) My impression is that the general approach will be to have BLE appear to the consumer as being as similar as possible to "classic" Bluetooth. For connection-oriented communication, you need to manually initiate the initial pairing/bonding, and after that, whether the devices will automatically connect once they get in range is described in the profile.

    For the Proximity use-case, then connections would obviously automatically happen, otherwise the use case is meaningless. You would have to initially pair your phone and PC of course, both for security and other reasons.

    2) On the CC2540, maintaining the connection is likely to use a bit less current, as you only need to be in RX on one frequency once a second to receive the transmission from the master, and slave latency means you do not necessarily need to TX if you do not have data to send. If you use advertising, then you need to access all three channels, so there will be more time spent in TX mode. So, I would say maintaining the connection is less power-hungry.

    Best regards,

    Karl