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Scatternet support from CC2540

nh6987
Intellectual 370 points

Other Parts Discussed in Thread: CC2540, CC2560, CC2530

Hi all,

We are planing to adopt low-energy Bluetooth CC2540 module for our home automation. There are two questions that I could not answer by googleing, hopefully someone here will help us:

- Does CC2540 bluetooth stack support scatternet (adhoc network)?

- CC2540 compatible with other consumer bluetooth products? I mean CC2540 has similar physical layer with one from, e.g. phone, laptop? Do I need a gateway to keep them interoperate?

Many thanks.

Nguyen Quoc Dinh

  • 0
    Intellectual 370 points

    Does someone here give me a hit!!!

  • 0 in reply to nh6987
    TI__Genius 10955 points

    You would have had a better chance of a reply if you had posed in the correct forum, which for CC2540 is the Low Power RF Bluetooth® Low Energy & ANT Forum.This also gives an indication of the answer: The CC2540 is a single mode Bluetooth Low Energy (BLE) device, with the limitations that follows from that.

    Scatternets are not supported in Bluetooth Low Energy.

    Existing products do generally not have BLE support. As far as I know, some new cellphones have the PHY support, but not yet the stack support in their OS. I am not aware of any legacy Bluetooth (BR/EDR) to BLE gateways. To connect to a PC, you may use the CC2540 USB dongle to talk to another CC2540 in an end device.

  • 0 in reply to hec
    Intellectual 370 points

    Hi HEC. Sorry for entering the wrong room.

    Related to the BLE and the stack provided from TI: Does BLE stack provide solution for adhoc network or multihop network? It's quite limit in case of just star network when the device is class 2.

    Many thanks.

  • 0 in reply to nh6987
    TI__Genius 10955 points

    Again, ad hoc or multihop networks are not supported in BLE to the best of my knowledge.

    Since you request features which are not present in BLE, it looks to me as if you want a "standard" Bluetooth decive (BR/EDR), and not BLE. In that case you could look into the CC2560. For that device, you are in the correct forum. I can not give you further information on that device, but my colleagues who follow this forum can.

  • 0 in reply to hec
    Intellectual 370 points

    Thanks HEC.

    Just wondering why ti's forum separate "standard" Bluetooth and BLE!

    We actually wanna take advantage of BLE in term of energy and monetary cost. Since BLE stack itself does not support multihop, do you think that we can build adhoc from application layer?

    Do you have any idea or suggestion to make communication range go over 1-hop.

    The best.

  • 0 in reply to nh6987
    TI__Genius 10955 points

    I think the main reason for separating the forums is that the devices are developed and supported by different groups within TI. For "hands-on" questions, that works fine, while for questions going more into system design, like yours, where the choice of device may not be final, it is less optimal, and you may end up being sent from one forum to another.

    BLE is a star network with one master and one or more slaves. It means that it is not possible to make this kind of system. I suppose it could be possible to realize it in the application layer by using role switching, but this would be very creative use of the BLE spec (the BLE spec actually forbids the same device from being a master and a slave at the same time, so you would have to make it look like two devices), and it is not supported in TI's BLE stack.

    Are you certain that Bluetooth is the best choice for you? You could look into Zigbee, where multi-hop is an integral part of the stack. The cost-of-build for a Zigbee device based on CC2530 and a BLE device based on CC2540 should not be too different. You may however find that some of your devices in a Zigbee network need to be receiving all the time, which may be a problem for power consumption (depending on the details of your application).

  • 0 in reply to hec
    Intellectual 370 points

    Thank for your assistance, HEC.

    We are in the choosing platform.  BLE is not a good choice with our requirement, i.e. backcompatible to existing bluetooth device and working in star topology only. Zigbee is neither our preference. We are thinking about 6LoWPAN ...

  • 0 in reply to nh6987
    Prodigy 190 points

    According to the Bluetooth Core v4.1, Pg 182

    "An LE device is permitted to belong to one or more piconets at a time, that is, an LE device may be a slave in zero or more piconets and may also be a master of another piconet."

    Does that mean that LE supports Scatternet?
    As per my knowledge, a device can either be a central or a peripheral at once.
    If a device  is a peripheral, then it can make only one connection as it is an 'LL Slave'. That means it can't connect with any other device. So how can it be a master in another piconet, since for that it will have to be a Central (LL Master or connection initiator)?

    I am really confused with GAP Roles.

    Is there any descriptive document that describes all the cases of roles and connections in a simple tabular for with examples ?

  • 0 in reply to Pranjal Saxena
    TI__Guru 57865 points

    Hi,

    The core specification version 4.1 have new GAP features compared to the version 4.0. One of those is the addition of multiple LL states that allows piconets.

    At this point, CC2540/41 with BLEv1.4 stack is version 4.0 compliant. The new 4.1 features will be added by software in the future stack releases.

    Best Regards

    Joakim