Platform Eases Hands-Free Bluetooth Design

What if you could truly have hands-free cell-phone operation while driving down the road? Better yet, imagine that this capability was inexpensive, yet provided high sound quality. Texas Instruments believes that most cell-phones users would welcome such a feature in their automobiles. This conviction prompted the company to introduce a new Hands-Free Kit (HFK) development platform (see figure).

Through the use of this kit, TI envisions the creation of a small, unobtrusive device that would clip to the car's sun visor. The device would connect to power via an AC cord plugged into the car's cigarette lighter. This potential product would implement a speakerphone—perhaps with voice-based dialing. Bluetooth technology would wirelessly connect the driver's cell phone to this device.

According to TI, this consumer device is only one of many possible products that could be developed by integrating digital-signal-processor (DSP) and Bluetooth technologies. In line with that thinking, the company has introduced the Hands-Free Kit development platform. It will implement real-time voice and audio-enhancing algorithms. At the heart of this kit is a business-card-sized board (1.65 × 3.7 in.). That board combines TI's TMS320VC5407 DSP, which runs at 120 MHz, with 512 kwords of on-board RAM and 512 kB of on-board Flash memory (nonvolatile).

The available overhead on the C5407 DSP is in the range of 30 MIPS. This amount should provide sufficient headroom for implementing unique, product-differentiating features. Memory-wise, the DSP has a large internal ROM for program storage. That ROM helps to eliminate the need for external memory.

The HFK module also flaunts a dual-channel AIC24 codec, on-board microphones, a speaker, and an RF modulator output. The latter can be used to drive an FM channel on the car radio. This feature is important because it allows a caller's voice to be heard through the car's sound system. Consequently, no cumbersome external speaker would be required.

Thanks to an IEEE 1149.1 JTAG interface, the development kit is easily accessible to the XDS series emulator from TI as well as various JTAG emulators from Spectrum Digital (www.spectrumdigital.com). The software drivers that permit Spectrum Digital emulators to operate with TI's Code Composer Studio software are provided along with their emulators.

For any voice-recognition system, noise suppression is vital to success. In the high-noise environment of an automobile, however, noise suppression is even more critical. To deal with this issue, each HFK development kit contains Clarity Technologies, Inc.'s (www.claritytechinc.com) Clear Voice Capture (CVC) echo- and noise-suppression software. CVC provides full-duplex echo suppression that allows the user to speak in a natural, conversational voice.

When used in conjunction with the Bluetooth daughtercard from Taiyo Yuden (www.ty-top.com), the HFK development kit enables the design and demonstration of hands-free speech-recognition technology. The daughtercard integrates TI's BRF6100 Bluetooth chip and Stonestreet One's (www.stonestreetone.com) Bluetopia software stack. The BRF6100 incorporates Bluetooth baseband and digital RF technology, which helps to decrease the size and cost of the daughtercard.

On the software side, Bluetopia provides a protocol stack that includes the Host Controller Interface (HCI), Logical Link and Adaptation Protocol (L2CAP), Service Discovery Protocol (SDP), RF Serial Communications Port Emulator (RFCOMM), and Object Exchange (OBEX) functionality. With such a protocol stack, designers can quickly begin product evaluation and development. The Bluetopia software also offers useful profiles like handset, hands-free, generic access, and serial port.

The HFK Development Platform (TDMSHFK5407) is available now for $1495. It includes the C5407 DSP motherboard with CVC software from Clarity. The Bluetooth Daughter Card Kit (TMDSBTC), which also is priced at $1495, will be available in the third quarter of this year. It includes the Bluetopia stack from Stonestreet One.

Both the development platform and daughtercard include a board-support package that includes Code Composer Studio (CCStudio) library examples, application notes, and user guides. Also provided are a full set of schematics, which are useful for immediate development. Royalty-free evaluation and testing licenses are available for the software from Clarity and Stonestreet One. Developers must have access to CCStudio v2.2, a JTAG emulator, an amplified speaker, and a microphone for implementation.