Description of the VSCP over the MiWI IEEE 802.15.4 protocol

Preliminary

MiWi is Microchips solution to get a simpler protocol then Zigbee according to IEEE 802.15.4. MiWi documents can be found here.

There are no special requirements other then that nodes on a MiWi net should preferably implement CLASS1.PROTOCOL, Type=40 and CLASS1.PROTOCOL, Type=41 to losen the burden of the PAN coordinator to resend all events to all node. For example a temperature node is normally not interested in anything else then CLASS1.PROTOCOL and it is a waste of bandwidth to send other events to it if the PAN know it just will through them away.

The PAN must have buffers and intelligence to be able to handle event filtering for all connected nodes. A standard node however does not need to have this extra burden.

There is no requirement for a node other then the PAN and coordinators to be active all the time. However all nodes must at least send a one minute heartbeat. CLASS1.INFORMATION, Type=9. After a node sent an heartbeat the node should be awake for a minimum of five seconds ( Time value may change) and receive any collected events intended for it.

Just as most other VSCP devices, VSCP MiWi devices need a n initialization sequence. In this case the intention of the sequence is to hook together a node and a PAN. This is typically done by activating a discover mode on the PAN and then press a button on the node that should be connected to this PAN.

The 802.15.4 payload is max 122 bytes. This payload can carry one or more VSCP events. The first byte tell how many events there is in the frame.