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Advancements in dashboard graphics

Posted: 10 Dec 2013 ?? ?Print Version ?Bookmark and Share

Keywords:TFT-LCD? dashboard instruments? colour display? microcontrollers? Graphic Display Controller?

Automotive manufacturers are replacing or augmenting traditional dashboard instruments with virtual instrumentation rendered on a TFT-LCD panel. The result is not only a novel selling point, giving owners the ability to customise their user experience similar to "re-skinning" a smartphone, but is also effective in helping to manage increasing quantities of driver information more effectively.

As far as customisation is concerned, this emerging generation of in-car instrumentation gives car makers the opportunity to tailor vehicles for specific markets, or offer "limited-edition" models, cost effectively and with fast time to market. Owners, too, can enjoy the option to personalise the look and feel of the instrument cluster display, which may be sporty, luxury, economic, retro, or any other creative theme.

From a more functional point of view, the graphical instrument panel can adapt to prioritise relevant information depending on context. Examples include switching to a rear-looking camera feed during parking manoeuvres when other data such as speed and engine rpm are not needed, or temporarily overriding the instruments during "normal" driving to present high-priority warnings. In this way, graphical instruments help provide maximum assistance while avoiding driver overload.

In an increasing number of today's models, at market levels from prestige to lower mid-ranges, part or all of the instrumentation is now presented via a TFT-LCD colour display panel. Typical display sizes can range from 3-inch up to 8-inch (or larger in high-end models), and may be used in a variety of ways ranging from a small auxiliary display sitting alongside conventional main dials up to a fully graphical unit with virtual dials featuring rotating pointers (figure 1). Desire for larger display sizes capable of presenting more information in a user-friendly layout, and of giving stylists greater creative freedom, place increased demands on the graphics chips at the heart of the system.

Figure 1: Fully graphical instrumentation featuring large-size colour TFT-LCD panel.

Graphical-instrument control challenges
A TFT-LCD controller capable of supporting typical screen resolutions of 800 x 480 or sometimes higher is becoming more common in today's microcontrollers, particularly high-end multimedia-oriented devices. However, all-in-one microcontrollers suitable for automotive driver information applications must be capable of overcoming complex challenges such as graphical rendering of rotating pointers, provide automotive industry-standard anti-tamper/anti-hacking security, and in addition should provide the flexibility for vendors to optimise the features and price for various markets; for example by minimising memory requirements and permitting lower-cost TFT-LCDs.

In addition, functional blocks supporting high-performance graphics effects such as perspective transformation, as well as built-in multi-channel stepper-motor control for conventional dials, are valuable features that help to create a strong all-in-one microcontroller suitable for the task.

Clear pointers
Graphically rendering the rotating pointer of a virtual dial is a complex undertaking, since the end result must be lifelike and visually pleasing to the user in order to be acceptable in the automotive marketplace (figure 2). Care must be taken, for example, to avoid unwanted stroboscopic effects which can be distracting for the driver and will attract unfavourable comparisons with conventional dials. Toshiba has overcome this challenge with the patented stroboscopic compensation feature in its Capricorn-Bt0/1 all-in-one microcontrollers, which are designed specifically for automotive advanced instrumentation applications. The stroboscopic compensation is based on a hardware bitmap rotation block, which handles overlaying of the rotated pointer onto a graphical background with angular resolution as fine as 0.1. A filtering algorithm is implemented to optimise the appearance of the pointer.

The Capricorn microcontrollers also integrate stepper-motor control interfaces, thereby providing the flexibility to support projects combining advanced graphical effects with conventional physical dials.

Figure 2: Rotated pointer as an overlay.

Inside the graphics engine
To help manage system cost and provide flexibility for manufacturers to differentiate products for various market sectors, some of the microcontrollers in the market today provide special features that help minimise memory requirements and boost performance when a low-cost display is connected.

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