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What is MiWi | Microchip Wireless Networking protocol basics

This page describes what is MiWi and mentions basics of Microchip Wireless Networking protocol(MiWi protocol) including MiWi network, MiWi protocol frame and its fields

The Microchip developed MiWi™ protocol is very simple and used for short distance communication. It supports low data rate and helps in creating low cost networks. MiWi is the short form of Microchip Wireless networking protocol stack.

Initially the MiWi protocol was developed for WPAN based networks. Later on it has been enhanced to support Microchip designed RF transceivers. This MiWi protocol is one of the alterantive used as wireless commnication.

MiWi Protocol serves small size networks with small applications which requires few hops between them. All the wireless protocols are supported in MiWi™ Development Environment.

MiWi uses MiMAC interface which helps to communicate with RF transceivers developed by Microchip. It uses MiApp interface in order to interact with the application layer. MiWi protocol supports all the Microchip proprietary RF transceivers working on different bands.

Following table mentions features of MiWi protocol.

Feature MiWi protocol support
Frequency of operation 2.4 GHz, subGHz ISM Band
Maximum network nodes supported 1024
Number of childrens per coordinator 127
Maximum coordinators in a network 8
RTOS and application independent Yes
Compilers supported MPLAB® C18, C30, C32
PHY, MAC Standard As per IEEE 802.15.4 standard
Network configuration Star, Cluster Tree, mesh

Let us understand terminologies used in MiWi Protocol such as "cluster" and "socket". "Cluster" in MiWi refers to group of nodes which will form network. The cluster can have maximum of 3 nodes. It is controlled by single clusterhead. Here clusterhead functions as PAN coordinator.

The other term "socket" refers to virtual connection between two MiWi devices. By using the concept of sockets, nodes in the MiWi network will find communication partners dynamically even without any information about them.

MiWi Network

MiWi network

The protocol uses acknowledged data transfer mechanism in MAC layer. The MiWi protocol there are three devices based on their individual functions in the network namely PAN Coordinator, Coordinator and End Device. Following table-2 mentions their details.

Device Type Functionality Functions/roles
PAN Coordinator FFD One per network. Forms the network, allocates network addresses, holds binding table.
Coordinator FFD Optional. It helps in extending the physical range of network.
End Device FFD or RFD Performs monitoring and/or control functions.

The PAN coordinator is the device which starts the network. PAN coordinator also selects the channel and the PAN ID of the network. All other network devices wanting to join onto the PAN need to obey the instructions of the PAN coordinator. There are three different kinds of configurations which exist in MiWi network viz. star, cluster tree and mesh type. The same have been depicted in the figure-1.

MiWi Protocol Format

Header of MiWi protocol frame

Before we understand MiWi protocol frame, let us understand three address types used in MiWi network viz. EUI, PANID and short address.
EUI: This is global unique address of size 8 byte. It is the short form of Extended Organizationally Unique Identifier.
PANID: This is the address which defines a group of nodes. It is 16 bit in size. All the nodes in the personal area network share the same common PAN-ID.
Short address: This 16 bit address is used as device address and it is assigned by its parent. This address is unique within a PAN and it is used for addressing and messaging purpose within a PAN network. PAN coordinator always has an address of 0000h. All other addresses are taken care by the coordinator.

Header of MiWi protocol frame consists of following fields:

Hops: This number indicates number of hops. It indicates hops through which packet is allowed to be re-transmitted.

• Frame Control:This bitmap defines the behavior of the MiWi packet. It is of 1byte length.

• Dest PANID:Indicates PAN-ID of final destination node. It is 2 bytes in size in MiWi protocol frame.

• Dest Short Address: short address of final destination node.It is 2 bytes in size.

• Source PANID: The PAN-ID of node which has origined the packet. It is 2 bytes in size.

• Source Short Address: The short address of the node which has originated the packet (2 bytes).

• Sequence Number: A sequence number which is used to track the status of the packets as they travel through the network till the destination. It is 1 byte in size.

• Report Type and Report ID: The protocol carries packets between the devices using special packets known as "reports". The MiWi protocol allows implementation of 256 Report Types. There are 256 different Report IDs can be assigned for each Report Type.

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