Automotive Electronics
A scalable system architecture
Andreas Grimm and Jurgen Betz from Fujitsu look at how the growing influence of mobile technology is extending into a vehicle’s instrument cluster
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n recent years, the world of mobile terminals has undergone a revolution when it comes to the graphical visualisation of applications and interface designers are discovering new ways of ensuring that their automobile brands make a lasting impression. It is in the area of instrumentation that new challenges are being presented for engineers who are looking to provide a scalable platform while minimising costs.
The traditional instrument cluster in the mid-range automotive segment is a combination of round instruments and one or more colour displays. In this hybrid concept, the dimensions and resolution of the displays are increasing with each generation of vehicle. The trend towards programmable instrument clusters in the high-range segment is well established and is proving increasingly popular. More and more automobile manufacturers are offering this type of ‘driver workspace’. These systems are based on a single large display covering the entire instrument cluster area. A high-resolution display gives drivers the opportunity to visualise the required content however they wish depending on the driving situation. These two versions can mutually replace each other and should therefore be based on the same system architecture so that the existing synergies can be utilised early in the development phase. What they have in common is a graphical user interface.
14 September 2011
Man/machine interaction In both segments, the central display medium in the driver workspace is formed by the graphical elements on the display. In 2D technology, the graphics are pre- rendered and stored in the system, while in the 3D world, objects are rendered at runtime. The simultaneous use of both technologies makes it possible to combine the benefits of both worlds in one application. Hybrid and programmable instruments use the same menu functions as, for example, radio/multimedia, navigation, night vision information or even simple status information.
One of the typical menu functions is the obligatory Coverflow that can be displayed in both 2D and 3D. The navigation map is usually generated by the head unit and either sent via a simple pixel link, such as APIX (Automotive Pixellink), to the cluster or is transmitted via a standard vehicle bus. Camera-based functions in driver assistance systems are generated in another controller and loaded into the cluster. A vehicle model is displayed for information from a system check or an operating manual. Generic requirements for such a model include turning around its own axis, opening of doors and the boot and the magnification of specific areas to increase the depth of detail. A three- dimensional vehicle model enables this level of complexity and versatility. With an average number of 30,000 polygons and a
Components in Electronics
refresh rate of 30 Hz, the model can be displayed fluidly and in excellent quality and additional polygons and textures for the model can be downloaded at runtime. However, when it comes to displaying information such as road speed, engine speed (rpm), temperature or fuel level, the two versions have fundamental differences. While the relevant information is displayed with stepper motors in the hybrid instrument, this data appears in a full graphics display in the programmable instrument cluster. In this cluster, the typical pointer-type instrument is one of the greatest challenges because the eye is very sensitive to rotational movements. It is necessary to maintain a constant refresh rate of 60 Hz in each individual scene. 2D can be used here. Even if the pointer-type instrument changes the shape, angle or size of the scales during operation, the storage space required remains small. With this version, each individual image can be processed with maximum quality and be called up by the system.
The additional Authoring Tool ‘CGI Studio’ is also still available for graphical adaptations in both 2D and 3D. This development environment is the mediator between the professional interface design tools and the system environment. Graphics can be imported and scenes modified easily and loaded seamlessly to both target systems.
Modular system architecture In the high-range segment, for example, the programmable instrument cluster features a display with a resolution of 1600x600 pixels, while the hybrid concept features a display with a resolution of 800x600 pixels. In the mid-range version, the display can also be combined with stepper motors for the pointers. Both systems can optionally be combined in parallel with a head-up display, for example with a resolution of 640x480 pixels, and a third display with the same resolution as the programmable instrument cluster. Video sources from infotainment systems or camera signals from assistance systems can be connected via direct parallel video inputs or Ethernet or MOST.
At the heart of this scalable platform is a dual system architecture based on a controller module using the MB9DF125 ‘Atlas-L’. This architecture is supplemented by a graphics module with one of the components from the MB86R1x family. The MB9DF125 ‘Atlas-L’ microcontroller has an ARM Cortex-R4 core and is responsible for the basic functionalities and warning symbol display. In the hybrid concept, this component also controls up to six pointer-type instruments in parallel. This controller features an integrated Cryptographic Services Engine (CSE) in accordance with the public SHE specification (Secure Hardware Extension). This implementation protects against
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