Taking The Guesswork Out

By using modern protocol analyzers dedicated to testing Bluetooth applications, manufacturers can speed the design, verification, and testing process without fear of jeopardizing quality. Up until recently, though, Bluetooth protocol analyzers could only operate by way of “air sniffing” the wireless link between devices or by “HCI sniffing” (Host Controller Interface) the wired connection between the CPU and the Bluetooth chip inside the device.

While examining each link individually provides valuable information, it does not go far enough. Fully featured protocol analyzers can air sniff and HCI sniff both sides of the Bluetooth chip simultaneously, greatly enhancing the debugging and verification process. Modern protocol analyzers go one step further in simplifying debugging by providing what is known as “virtual sniffing” where the analyzer does not physically tap the link.

Virtual sniffing is an alternative to traditional HCI sniffing. Instead of a wired tap of the link between the CPU and the Bluetooth chip, virtual sniffing uses a software connection to supply the communication packets to the protocol analyzer. This process simplifies debugging for the engineer because often it is not convenient to physically tap the link. Virtual sniffing also allows the use of less equipment (no probe required to tap the link) and therefore lowers cost.

“Some of our testers, who do not read the Bluetooth spec, had no trouble confirming the data sent through the air. All it took was some simple, standard operating procedure training,” Chang says.

Unlike protocol analyzers that can only store data for later evaluation, today’s analyzers feature real-time displays to further accelerate the debugging and verification process. The effect of user actions, whether “positive path” or regressive, are observed as they take place.

For instance, the consequences of rapidly pushing a volume button or of moving a mouse are immediately seen on the screen of the analyzer. The test engineer no longer has to rely on notes or memory to reconstruct what took place when attempting to fix any problems.

Fully functioned protocol analyzers can also extract the audio data transmitted between a Bluetooth headset or a Bluetooth automobile hands-free unit and a cell phone and place the data into a WAV file. Streaming stereo music going from an MP3 player to a stereo headset can also be extracted into a WAV file. Once the audio data is in a WAV file, many options are available for analysis of audio quality.

“This ability helps us support the customer,” Watson says. “We can ask them to get an air trace and pass it on over to us. From there, we can point out, ‘Well, if you look at line-packet number 1432, you’ll see that this is what’s happening, what’s going on, etc.’ At that point we can work on ironing out the errors between the connections.”

The Wireless Future

The Bluetooth revolution will continue on the strength of its marketing and technical advantage, as both consumers and industrial users recognize the value proposition of working without cables. Manufacturers who wish to capitalize on this trend can help ensure success with the use of today’s modern protocol analyzers, especially those that can support the newer features of Bluetooth such as Secure Simple Pairing, which simplifies the pairing process while tightening security.

“The ability to offer Bluetooth solutions with confidence has definitely improved our product offering,” says Chang. “Now, 50% of our cell phone chips are bonding with Bluetooth. It means that our customers prefer Bluetooth technology. It makes their phones more competitive.”

Frontline Test Equipment, a provider of PC-based protocol analyzers for special-purpose data communication networks, offers a good example of a Bluetooth protocol analyzer (Fig. 1). Its FTS4BT Bluetooth analysis technology is even licensed by the Bluetooth SIG for use within the SIG’s product qualification tool.

David Rizzo, DPM, is a technical writer based in Torrance, California. He has written two trade books, 150 technical articles, and 300 newspaper columns. He can be reached at droadmap@pacbell.net.

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