Electronic Design

Wireless UART Chip Set Goes Frequency Hopping In The ISM Bands

Most engineers aren't wireless wizards. But with virtually every electronic product going wireless, engineers need faster, easier ways to meet the challenge. To help solve the problem, Texas Instruments came up with the Dolphin chip set. The company says that Dolphin gives designers a simpler method for making designs wireless.

The set uses frequency-hopping spread spectrum (FHSS) in the 902- to 928-MHz industrial-scientific-medical (ISM) bands, designated by Part 15 of the Federal Communication Commission's regulations (see the figure). It targets industrial/commercial telemetry and control as well as home automation. Other applications include PC peripherals, consumer electronics, and personal healthcare.

The Dolphin chip set's TRF6903 radio transceiver takes advantage of frequency-shift keying (FSK) to transmit data up to 38.4 kHz with programmable baud rates. The FHSS mode of operation improves reliability, resistance to noise, and interference. It also increases range in one of the most widely used license-free bands.

But what makes Dolphin so easy to use is the DBB03 digital baseband ASIC. It contains all FHSS logic as well as the physical, media-access-controller, and data-link layers of the communications protocol. There are 16 hopsets of 50 points each. Note that in FHSS, transceivers with different hopsets can't communicate, making it possible for more users to share the spectrum.

There's also no need for engineers to make up their own protocol. The firmware supports point-to-point and broadcast modes. The system handles up to 65,536 transceivers, each with its own unique ID in addition to a network ID and system ID.

The DBB03 communicates with the application's external microcontroller, such as TI's MPS430, by way of a standard UART interface. Designers need only supply their data in asynchronous chunks with start and stop bits. Using the TRF6903 by itself, the output power is +7 dBm. With an external power amplifier (PA) and a 3.6-V supply, the output can jump up to +23 dBm. The higher power can extend the range to as much as a mile in open-space conditions.

The Dolphin development kit contains two reference designs. One is for low power, and the other uses an external PA for higher power. Both designs are FCC pre-certified. The kit includes Gerber files, schematics, bills of materials, and evaluation software.

The Dolphin chip set costs $4.50 in 1000-unit quantities.

Texas Instruments
www.ti.com/ismrf

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