A powerful Bluetooth development tool has helped Sound ID to commercialize an innovative headset for the hard of hearing, which employs wireless communications to link an in-ear module with a remote microphone.

The xIDE software development kit from Cambridge Consultants allowed Sound ID to eliminate the need for a separate microprocessor in its in-ear headset, by fully exploiting the 'free' processor that comes as part of the Bluetooth chip to control the overall hearing system. This resulted in considerable savings, in terms of both real estate and the bill-of-materials. The approach also substantially reduced power consumption — another critical area of performance for this type of product

Sound ID's Personal Sound System looks like a small Bluetooth mobile phone headset. However, inside the device is a DSP that can be configured by an audiologist, or the user, to amplify sound based on individual preferences. The Bluetooth capability allows the ear module to link with a remote microphone that can be positioned to improve signal-to-noise ratio. It also acts just like a standard Bluetooth headset for a mobile phone, automatically switching from continuous amplification mode, to 'hands-free mode' when a call is in progress.

The Bluetooth chip used is CSR's BlueCore device with embedded Flash memory, which includes an on-chip XAP RISC processor. This processor's main task is to manage the Bluetooth protocol communications. But it has enough spare computing power to allow it to function as the application processor in a small hostless Bluetooth system such as a conventional headset, running software such as a hands-free profile and controlling a simple man-machine interface.

However, Sound ID's new sound system is much more sophisticated. The versatility of the ear module means that the processor has to run four types of Bluetooth application software: hands-free and headset profiles for open connectivity with mobile phones, a custom profile that passes audio between the companion microphone and ear module, and a serial port profile for connecting to a PC for initial configuration. In addition, the processor controls the overall system, including the DSP, and user interface buttons and beeper. This includes managing configuration software that allows the DSP's amplification and spectral shaping characteristics to be personalized, and different sound settings to be selected during use.

The ability to perform all these functions was made possible by Cambridge Consultants' xIDE software development kit (SDK). This gives unrestricted access to the full native power of the XAP processor inside BlueCore, allowing users to bypass a software 'safety' layer that serves (for less experienced programmers) to protect the Bluetooth compliance of the chip. To help speed the project, Cambridge.

Consultants also contracted to write the application software for Sound ID, providing a complete system running on XAP that manages both the Bluetooth protocol communications and the sound system requirements, without compromising Bluetooth compliance. Cambridge Consultants also incorporated power conservation techniques to minimize the consumption of the system.