Mesh-radio-for-Bluetooth development kit
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.
CSR’s Walker says that its developers have demonstrated that messages can be sent from one end of a multinode network, and acknowledgement returned, with reliability and with low latency. There are features of the network you can exploit, he notes; some nodes will (by reason of their function) have access to mains power, and can therefore afford to be “awake” for longer; and also, you can set up parameters such as number of repetitions, or message validity duration. That is, loosely speaking, a node may say, “I have seen and repeated this message x times, and will ignore it if it appears again,” or, “this message is y msec old and therefore out of date, so it should not be re-broadcast.
The CSRmesh Development Kit will include a set of tools for evaluation and software development – software will be downloadable – and will comprise development boards, the CSR xIDE software development environment, USB programmer and interface cables, example CSRmesh applications for the development board, and – to Rick Walker’s main point about the power of the Smartphone – example host applications and source code for Android (at launch) and Apple iOS (in development).
Development boards will host a CSR1010 IC with 64k EEPROM; PCB antenna, RGB LED, two user pushbuttons and one user slide switch, a power switch and an SPI programming connector. Pads are provided to connect external devices.
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