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RF/Microwave??

Chipset automates wireless links

Posted: 08 Apr 2005 ?? ?Print Version ?Bookmark and Share

Keywords:texas instruments? ti? dolphin? wireless universal asynchronous receiver/transmitter chipset? uart chipset?

Perhaps they called it Dolphin because it is smart, or it can do tricks that similar creatures cannot. Whatever the reason, the High Performance Liner (HPL) group at Texas Instruments (TI) turned its attention to simplifying applications development for frequency-hopping, spread spectrum (FHSS) 915MHz systems with its Dolphin wireless universal asynchronous receiver/transmitter (UART) chipset.

The two-chip set consists of the TRF6903 RF transmitter and the DBB03 digital baseband ASIC. The most interesting part of the story rests with the baseband ASIC, which has on-board firmware fixed in ROM that incorporates the algorithms for frequency hopping and clock recovery. "It effectively does all of the housekeeping and control of the RF transceiver," explains Dave Wilson, manager for TI's HPL group. "So, instead of doing extensive digital baseband processing, designers simply need to write to a few registers to quickly set up the chips."

The team developed this chipset because they had customers asking for a low-cost ready-made solution that would allow them fast time to market with low-cost products for wireless automation, industrial control, as well as medical and consumer systems. The chipset can be teamed as a UART connection with any host microcontroller to handle applications level functionality.

One of the other things that designers can avoid by using this device is toeing the line to meet FCC guidelines on frequency hopping. "It's very easy to violate FCC guidelines for frequency hopping algorithms and how much output power you can transmit," warns Wilson. "Basically, if you use this chipset and follow our guidelines, you should sail through FCC certification."

The chipset competes with ZigBee, but the Dolphin chipset allows customer to develop their own proprietary system rather than using a standard. Are there any advantages to that? "We have a lot of customers who would prefer not to be compatible with ZigBee, so that their links can be more secure from competition," says Wilson. He adds that a proprietary product can be very simple with low overhead, and it allows systems designers to develop their own proprietary systems and realize competitive advantages.

Since it is a hardware manufacturer, the most challenging part about this project for TI was implementing the software. To accomplish this, they trained engineers to get up to speed on the current software, joined several RF boards and committees, and worked closely with their Beta customers.

Flexibility
But, by incorporating the algorithms on chip, don't we give up flexibility? The team notes that the chipset can provide flexibility even though the programming is mostly done. For instance, the firmware supports point-to-point, broadcast, and pseudo-mesh networks. Additionally, the network can be partitioned. Each transceiver features a unique transceiver ID, network ID, and system ID, and up to 65536 transceivers can be configured within a single system. With network partitioning, only transceivers with the same system ID, network ID and hopset can communicate.

Range? Data rates?
Range can be either several hundred feet or up to a mile in free space, depending on the product configuration. The version with an external power amplifier delivers up to 23dBm output power and the one without delivers 7dBm output power. Over the air data rates are specified at 38.4Kbps. When the device is up and running, it is comparable in power consumption to other systems, but, when coming out of sleep mode it offers the advantage of a 200s channel lock time.

The chipset comes with an evaluation board, user guide, evaluation software, and protocol documents. Gerber files, reference designs, schematics and BOM are available on the company's website.

The chipset is priced at $4.50 each in 1,000-piece quantities. It is already available in production quantities.

- Janine Love
eeProductCenter




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