Mesh-radio-for-Bluetooth development kit

July 17, 2014 // By Graham Prophet
Smartphone control makes the difference, CSR says. The Bluetoooth silicon vendor announced earlier in 2014 that it had developed a mesh networking protocol to run on the Bluetooth Smart standard. The company is about to launch its development kit for engineers to begin using the protocol.

CSRMesh uses the company's µEnergy product family, and is a protocol running over Bluetooth Smart. It permits up to 65000 nodes in a single network, and multiple co-existing networks, and CSR intends that it be used in applications such as home automation; it has already been applied to lighting, and will be extended to other functions in the near future.

Asked what Bluetooth can bring to mesh networked systems, CSR’s Rick Walker – senior product marketing manager – says that above all else; it’s the smartphone. Virtually every recent smartphone, he notes, comes ready-equipped with Bluetooth Smart. Any phone can therefore host an app to directly interface with a network of devices, either controlling or collecting data. You do not need any form of gateway or additional hardware between the phone and the network.

CSRMesh is – in contrast to other network technologies that form specific routes through the network – a flood mesh protocol. That is, any device receiving a message either identifies that the message is for itself, or it re-broadcasts the message. CSRmesh does not use full IP addressing but adopts a light weight data structure which enables much lower power and lower processing burden for simple devices.

How does Bluetooth, in the shape of battery-powered nodes, implement a flood-mesh and still contain power such that long battery life is possible? It is, Walker says, all about minimising the time that each node spends “listening” - that is, with its receiver powered up and waiting for a message. In a typical home-automation context originating or repeating a message will be relatively infrequent event and therefore, less significant for battery drain; and CSR says that its µEnergy range already achieves this with low current drain while active. The Mesh protocol needs to maximise the probability of intercepting a transmitted message while minimising wake-to-sleep Rx ratios.