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BLE-git hub broadcast mesh

FormerMember
FormerMember

github.com/.../nRF51-ble-bcast-mesh

i found this link in git hub ....whether it is really make a Bluetooth mesh network with 20 nrf51 nodes.... is it really working.....? will it support in ip level also....?guide me with this set up...... Thankyou...

  • Hi, the bcast-mesh works well, but with some restrictions. The devices that are part of the mesh are required to be on-air for up to 99% of the time, making it unsuitable for battery powered operation. Also, the framework is not able to operate directly on GATT services outside of its own system.

    The mesh works by defining mesh-global data slots (think of it as a shared GATT server), that are synchronized across the mesh. Any device in the mesh may write to or read from the data slots, and as soon as a device writes a new value to a slot, the value is propagated through the mesh, so that all devices will have the same value in their local copy of the slot. The slots are stored as GATT characteristics in the Softdevice GATT server module, and is available to external devices through a regular BLE connection, as displayed in the Gateway example.

    Since the Bcast-mesh doesn't have any addressing features, the mesh network may be extended to any number of devices (10, 100, 1000, 10000 devices, if you want), but keep in mind that the propagation time and synchronization problems this causes may become an issue in larger networks. It should be possible to integrate the mesh into most existing S110 applications, given that they don't utilize the same on-chip resources. Note that the framework adds a "mesh-service" to the Softdevice GATT server, that will be available to external devices, along with your application specific GATT services. This mesh-service contains an array of data-slots; the previously mentioned "shared data-slots". You might have to change some initialization procedures as well, as the mesh-framework calls some GATT-server functions directly when creating its data structures.

    There are no immediate plans to implement IP support for the system, as the lack of addressing makes it fundamentally different from the IP-stack. Some gateway between the Internet and the bcast-mesh may still happen, though.

    For a quick start, take a look at the LED mesh example, which simply defines two data slots, one for each of the two LEDs on the PCA10001 board (or the red and green LEDs on the dongle), and synchronizes them across all devices in the mesh. The Template project is a great starting point for your own application, as it contains the bare minimum to get a new mesh-application up and running.

    Also note that the bcast-mesh is not a part of the official Nordic Semiconductor SDK, but rather a cooperation between Nordic Semiconductor and NTNU.

  • Hi Trond, do you have any data on the propagation time? Just curious is there were any measurements done to get a feeling of dependency on number of nodes with propagation time. thank you!

  • Hi, didn't see this until now. Propagation time is on average 75% of the supplied min_interval times the number of hops required to propagate the value. Worst case is min_interval (disregarding packet corruption), best case is 50% of min_interval

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