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Electrics/Electronics - Convenient Entertainment |
Integration of an MP3 Player Using Bluetooth
A new concept now makes it possible for drivers to use their car radio to operate an MP3 player while driving. The secret is a Bluetooth/CAN gateway that has been developed by Bertrandt in Cologne.
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More safety, more convenience
The integration of an MP3 player using Bluetooth technology offers several advantages. The main ones include improved safety on the road and more user-friendliness, as the player can now be operated entirely via the car radio. The user no longer needs to reach for the MP3 player, which often lies unsecured somewhere in the car.
The system is also extremely practical, as music no longer needs to be stored on numerous CDs but can be kept on a single memory card.
Integration via an existing interface
In order to connect an external device to the existing environment of the vehicle, Bertrandt used an already existing interface - that of the CD changer.
This interface is particularly suitable, as it has all the signals required for controlling an external audio device. Furthermore, it is already factory fitted in modern radios from different manufacturers and does not need to be installed as an extra.
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Development of a Bluetooth/ CAN gateway
Wireless integration was achieved by using a specially developed Bluetooth/ CAN gateway. This receives and processes the signals sent by the car radio via the CAN bus and transmits them via Bluetooth to an MP3 player (in test operation: a PDA from Hewlett Packard). Until now, it was necessary to use a stereo audio cable to transmit the audio data, as Bluetooth 1.2 was not able to transmit uncompressed audio data in a sufficiently high quality due to the low data transmission rate of 64 kBit/s. Now, the new Bluetooth standard 2.0+EDR with a transmission rate of 3 MBit/s makes wireless transmission possible. Decoding of the data takes place in the MP3 player. This means that different codecs (coder/decoder) can be used and replaced easily. The newly developed Bluetooth/CAN gateway can receive, process and transmit certain commands and data via Bluetooth and the CAN bus. It represents the main component of the system, as it forms the interface between the vehicle and the MP3 player. In fact, the entire system acts like a CD changer connected to the bus. In doing so, the gateway has to meet important manufacturer-specific specifications in order to be recognised as a CD changer by the radio.
New application allows remote control
The MP3 player used in the test was a PDA running on the Windows Mobile 5.0 operating system from Microsoft. The Windows Media Player included in the software package allows music to be played in a digital format. However, neither the Windows Media Player nor the operating system have an interface that allows remote control of the device. For this reason, an application for the PDA running on the .NET Compact Framework 2.0 was developed. This ensures simple portability to other Windows Mobile systems. In addition, the Windows Media Player was integrated into the application, as this is able to decode the most common audio formats such as mp3, wav, wma, etc., which means that no other audio decoder needs to be installed on the PDA. The application therefore has all the functions of a "familiar" multimedia player, while at the same time offering the functionality of a CD changer. The system can be controlled either externally, i.e. by the control commands transmitted from the radio or the gateway via Bluetooth, or using the Windows user interface, which allows easy and intuitive control. Status details such as playing time, track number, etc. are shown on the PDA display and transmitted to the gateway via Bluetooth, so that they can also be shown on the radio display. |
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Simple operation for safer driving
The complete system consisting of the gateway and the PDA was kept as simple as possible. The user does not need to worry about operating the equipment but can concentrate entirely on the traffic and enjoy the music. For example, the devices are connected automatically, just like the connection between a Bluetooth wireless telephone and a headset. The MP3 player needs to be registered only once by the gateway. In normal operation, it then connects automatically and is ready for use immediately. The music tracks are organised in play lists with a structure corresponding to that of a real CD changer with six slots.
The integration of an MP3 player into the vehicle has resulted in a comfortable and convenient solution that allows trouble- free enjoyment of MP3 music collections while driving. The driver is neither impeded nor distracted.
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