Electronic Design

Freescale's Busy Beestack

Freescale’s ZigBee 1321XEVK development kit is one of the best when it comes to targeting microcontroller-based platforms versus modules like those from Synapse or Digi. Freescale’ ZigBee stack is called BeeStack and is part of the package. The development kit is substantial, coming in its own case. The kit comes with not one but two types of remote modules — three large units and four smaller ones. Both are battery powered and have removable plastic cases, and are extremely well-designed with power switches, USB interfaces and sensors. From a programming standpoint, the two modules are essentially the same. The larger module, however, has an LCD screen while the smaller one has a complement of IO and buttons. The larger module also supports an external antenna. The modules contain MC1321x System-in-Package series that incorporate 40MHz HCS08 microcontrollers with an 802.15.4 RF transceiver. The chips are available with up to 60Kbytes of flash and 4Kbytes of RAM. Smaller versions can utilize different stacks while still retaining enough headroom for application code. The chip contains 16-bit timers, an 8-bit keyboard interrupt port, an 8-channel 10-bit ADC, a pair of 115.2Kbaud serial communication interfaces (SCI) with I2C support. It also has an on-chip clock and background debug module (BDM) support. The chip’s operating voltage range is 2V to 2.4V. Development Tools The modules are preprogrammed with a sensor and control demo application that is linked back to a PC using the supplied USB dongle, which works with Daintree Networks’ Sensor Analyzer (See "Sniffing Zigbee"). The demo and Daintree software made it very easy to get a feel for the capabilities of the system. The kit also includes P&E Microcomputer System’s USB-based Multilink BDM hardware debugger. The Quick Start Guide that comes with the BeeKit software toolkit targets this platform as well as other Freescale ZigBee development kits. It addresses installation and basic demo application operation. There are CDs for the BeeKit with ZigBee software, Daintree’s software, and a full copy of Freescale’s CodeWarrior for the HC(S)08. The latter is found on the demo modules, and works with the Multilink module — although only one unit can be debugged at a time since there is only one Multilink unit. The BeeKit software, which requires .Net 2.0, includes multiple wireless stacks including 802.15.4, SimpleMAC (SMAC), and ZigBee. SimpleMac simpler than ZigBee but more functional than basic 802.15.4. It is also more compact than the ZigBee stack. Installation was smooth and even included details about licensing — something often overlooked by other vendors. I was impressed with the ZigBee (BeeStack) stack documentation, which included plenty for getting started with the system, including an application guide as well as the usual API reference manual and distinct manuals for cluster design and debugging. I have already used CodeWarrior so I was able to dive right in to the sample applications. It was relatively easy to choose the type of stack, check out the various demos and get started with a simple custom app, though it took a couple of days to understand the range of software and tools that are included. Having used Daintree’s software before also smoothed the process. As with most ZigBee kits, I found it best to work with only one module and modify an existing demo before moving into a more sophisticated application. This is especially true since each of the modules is initially set up for a different function like a dimmer switch. While the tools are easy to use, the functionality is so high that it is easy to overlook features or techniques if you move too quickly to a custom design. Likewise, it may take some time to determine the kind of stack your application may require. It is easier getting started if ZigBee is mandated but the pain comes later when the system needs to go through the ZigBee logo process. Regardless of the application, the cost of the kit and the chips will be small compared to the other costs such as licensing and FCC approval. But that's true for any chip-oriented ZigBee solution. There is a 90-day eval license for the ZigBee stack, and the 802.15.4 and SMAC are available without this restriction. I didn’t find any holes in the software stacks or development tools, though I concentrated more on the modules. They were easy to interface with, though getting access to power was a bit of a pain with the larger unit. Oddly, it has separate headers for each port and no power header. Overall, the kit includes all the hardware, software, documentation and demos necessary to get up and running very quickly. Even batteries, USB cables and power supplies are all included. Related Links Freescale

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