Electronic Design

Microchip Makes MiWi

Microchip’s PIC microcontrollers are popular low power platforms that make an ideal match for low power 802.15.4-based applications. Microchip’s solution supports 802.15.4 and ZigBee plus its own homegrown MiWi solution. The latter only works with Microchip platforms but its functionality may make it ideal for proprietary applications. The PICDEM Z kit includes a pair of demo boards and the USB-based ZENA wireless network analyzer) and its software provides graphical displays of wireless network traffic. It can handle IEEE 802.15.4, ZigBee and MiWi protocols, employs a hardware packet sniffer and requires a PIC development platform like the MPLAB ICD 2. The demo boards contain a PIC18LF4620 microcontroller with 64Kbytes of flash memory and a typical set of PIC peripherals. The demo board can run off a 9V battery (not included). The daughter card includes the Microchip MRF24J40 RF transceiver and antenna interface. There is a patch area on the demo board. Making MiWi The ZigBee software stack supports reduced function devices (RFD), full function devices (FFD) and coordinator devices. There is a plain 802.15.4 stack but many developers are likely to choose the MiWi protocol that is built on 802.15.4. It is free from Microchip but only works with Microchip components. In theory, it is possible to link MiWi networks to other 802.15.4 networks but this is not provided by Microchip and it is a non-trivial exercise. ZigBee is likely to be used for cross-platform applications while MiWi provides much of the advanced functionality without the ZigBee overhead. Getting started is relatively easy. The modules come preprogrammed and the documentation thoroughly explains how to get started, followed by a nice section on extending the application and building your own. Microchip’s website contains applications notes for more tips. While all the protocol stacks are free, the MiWi stack is likely to be the one most will start with. It supports all network configurations including mesh networks, although more complex networks require a larger, more complex stack. Still, it tends to be much smaller than a comparable ZigBee stack. MiWi includes AES encryption security support like ZigBee but, again, MiWi-specific. Programming with MiWi is not really different from ZigBee at a functional level. One advantage of using MiWi is the support of the ZENA protocol analyzer. This kind of tool is invaluable for wireless development and it requires no special customization. Learning MiWi is comparable to ZigBee but there are some differences so choosing one early will save a good deal of time. Either way, PIC developers will be quite comfortable with the PICDEM Z and MiWi. Related Links Microchip

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