Hands Free Car Kit


Hands-free Car Kit (HFCK) is a Car Telematics and infotainment application for hands-free operation connecting any Bluetooth or non-Bluetooth mobile phone to a car. The system consists of a main unit, power supply, car interface, UI (User Interface), microphone and speaker.

This case study showcases Mistral’s capability in building a versatile, ready-to-use, small form-factor, low-cost, Bluetooth or non-Bluetooth HFCK reference design; which is extremely easy to install, and ideal both as an OEM solution or an after-market solution

The Customer

The customer is one of the world’s leading semiconductor companies specializing in high performance analog, mixed-signal and DSP chipsets.

The Requirement

The customer wanted a HFCK Platform using its newly released high-performance MSA (Micro Signal Architecture) processor; which executes highest quality of speech recognition and text-to-speech functionality.

The software framework defined for the HFCK system consisted of:

Speech functionality

  • Acoustic Echo Cancellation (AEC) & Noise Reduction (NR) Bluetooth interface
  • Voice Activated Dialing (VAD)
  • Text-To-Speech (American English) for voice guidance
  • Speech recognition (American English) for command/control

Communication System:

  • Mobile phone connectivity
  • Bluetooth connectivity to local mobile devices
  • Handset Address book synchronization with Bluetooth handset
  • Automatic Call answer after preset number of rings
  • Voice Guidance
  • Three key remote with LED indicator to accept/reject call, volume control & for incoming call.

Solution Provided

Mistral designed and developed the entire hardware platform for the HFCK system along with the following software:

  • The Complete BSP (Board Support Package) in modular structured APIs, to control the hardware modules on board. The Driver APIs remain the same for various flavors (as many as 6) of the hardware. With this modular approach, application developers are required to port their code only once. Subsequently, for newer scaled-up versions of the system designs, application porting is not needed
  • An “Application Framework” which supports concurrent applications across multiple vendors. The applications are completely insulated from the underlying hardware platform
  • A “System Executive” which handled the inbound/outbound data traffic on the HFCK platform:
    • The executive helps in proper switching between sub-applications, and guarantees system behavior in terms of response, response time, etc
  • A proprietary “Flash File System” that supports the following features:
    • Standard File operation API support with “seek” features
    • Multiple DAT files for HFCK application usage
    • Download / Upgrade / Delete boot images into the Flash
    • Download / Update / Delete DAT files (application specific) into the Flash
    • Fast boot time
    • The File System is portable across platforms/ flash technologies.