Electronic Design

eZ430 Goes Wireless

Texas Instruments (TI) MSP430 eZ430 kits (see $1 Arms And $20 Development Kits) have garnered support for additional target platforms such as QuickFilter’s SavFIRe (see Mid-Range Micro Kits. The eZ430-RF2500 adds yet another target to the mix. This time it is wireless. This development kit uses the same 2-wire Spy Bi-Wire USB debug unit like other EZ430 kits, but changes the target processor to an MSP430F2274 linked to TI’s Chipcon CC250 RF transceiver. This combination is not as ambitious as an 802.15.4 or ZigBee system but it is significantly easier to work with and very low power. It is ideal for point-to-point or star network applications. To that end, TI provides support for its SimpliciTI protocol. It is a simple, low-power RF network protocol aimed at networks with under 100 nodes, low duty cycle and limited bandwidth requirements. It is obviously targeted at battery-operated nodes. It has only 5 commands and uses under 4Kbytes of flash memory and 512 bytes of RAM. A complex system can handle up to 4 hops extending the range of the overall network, and it works with the Chipcon CC1xxx and CC25xx chips. Reception is line-of-sight and range is based on data rate. The chips transmit on the 2.4GHz band. The kit actually comes with a pair of target boards. It also includes a AAA battery-based package designed to power one of the target boards. It works great as long as you don’t solder an 18-pin header on the target board. That would provide another way of plugging the target board into a different host. The battery package does its own 6-pin header that provides access to the reset line and a serial port. The target board includes its own chip antenna. There are two small coverage blind spots at the ends of the bar antenna. The board also has a temperature sensor and some red and green status LEDs. There is also a pushbutton input. The target boards come pre-flashed with a temperature sensor application. This includes a simple PC-based application that communicates with the target board via the USB debug unit. Although the kit only includes a pair of target boards the application can track multiple remote units. The package comes with IAR’s Embedded Workbench Kickstart IDE (see Developing ARMs). It also comes with TI’s Eclipse-based Code Composer Essentials. The C demo firmware source works with IAR’s IDE. Installing the Windows-based kit is relatively easy. The USB debug unit is recognized and the CD includes the drivers. It works with both IAR’s Embedded Workbench and TI’s Code Composer Essentials IDE. I had worked on both prior to this evaluation. IAR’s Embedded Workbench is compact, fast, and easier to get up-and-running. Code Composer Essentials offers the extensions possible with Eclipse plug-ins. Both support C/C++ and assembler. Both can download and debug the target board using the USB debug unit. Your preference will likely depend upon prior experience. The target board demo application source is the easiest starting point. It addresses all the details that will likely be used in most applications. The SimpliciTI API is easy to deal with since it only has the basics like broadcast/address-based send/receive. Still, it is more powerful than most short range, low bandwidth applications will require. There is plenty of headroom on the microcontroller and the target board header provides access to most of the IO ports on the chip. Adding the header makes it easy to plug into a carrier board with additional off-chip peripherals. It has 256Kbytes of flash plus an additional 32Kbytes of flash and 1Kbytes of RAM, and runs speeds up to 16MHz. The serial port supports IrDA and LIN (local interconnect network) protocols and can operate as an SPI or I2C interface. There is also a 10-bit, 200Ksample/s ADC, a handful of 16-bit timers and GPIO ports. For a low cost RF application platform, the eZ430-RF2500 is hard to beat. Related Links IAR SimpliciTI Texas Instruments

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