Advanced graphics in automotive instrument clusters

Michael Staudenmaier, Freescale Semiconductor -September 20, 2012

The instrument clusters of today's cars show a clear trend away from electromechanical pointer instruments and toward solutions with significant focus on graphical displays. This paper provides an overview of automotive instrument clusters with advanced graphic capabilities - today and in the foreseeable future.

In this emerging field there is still a quick evolution ongoing driven by customer expectations influenced by graphical solutions from the consumer world. Bringing those expectations together with automotive quality requirements at affordable cost is still a challenge that has to be addressed by new methodologies and tools.

In this paper the discussion of instrument clusters is split into several topics: the use-cases, graphical techniques, technical implementations and design decisions taken in such complex embedded systems. As there are many techniques adopted from the PC arena a quick overview of selected areas is presented and its adoptions for the embedded world are outlined.

A focus is put on the creation of the graphical content and human-machine interfaces and the evolving tools support in that area. This paper shows several approaches and solutions for a smooth development flow starting from HMI graphics development down to optimized porting on embedded graphic accelerators.

While current designs focus on imitating classical pointer instrument clusters, this paper will show some upcoming trends and possibilities in the design of advanced user interfaces.

1 Introduction
In recent years the traditional mechanical automotive instrument cluster has been more and more extended by electronic displays. The first step in the evolution was the introduction of liquid crystal displays used for mileage information and other simple alpha-numeric information.

Figure 1: Alfa Romeo Giulia Spider Instrument Cluster.

The reduced prices of TFT displays and the availability of the required compute performance in the embedded space now allow affordable graphic based solutions. As the instrument cluster is one of the most prominent parts of the HMI and very evident to the driver it is an important differentiation feature for the car manufacturers. For high-end cars this leads to the situation that manufacturers are significantly increasing the level of investment into that area. Currently TFT displays in that area still seem to be considered an added value in itself by the driver as it is considered a high-tech feature.

Since the "gauges with moving pointers" visual paradigm is well accepted by consumers and can very quickly communicate both speed and acceleration to the driver, it is necessary to simulate the mechanical instruments using advanced graphic technology. Exploitation of additional possibilities is just at the beginning, although there is a huge potential for improvements in that area. An obvious example is the reconfigurability of the graphics based dashboard which is a key advantage. The display content can be changed based on the context, which is not the case with mechanical gauges. Looking at consumer industry products it is obvious that well defined user interfaces are a key differentiation factor already today.

The general idea behind any optimization in that area is to display more complex information in a simpler way- the ways to achieve this maxim for the automotive cluster is currently an evolving area. The advantages are not solely technical, there are also commercial aspects. The graphic technology easily allows adding branding to the dashboard. Potentially it could even open new revenue streams by allowing the use of skins for the HMI or enabling the download of additional applications.

Automotive dashboards with graphic displays impose new technical challenges on the development of such solutions. The level of complexity is increased by at least one order of magnitude. While the graphic technology used in that area itself is adopted from the PC arena its application in the car is new. This requires new skills from the development teams and quite some time to go through a steep learning curve.

Consumers are used to PC graphic quality, but the fact that the compute performance in PCs is well beyond what is available in the embedded space makes rendering close to photo-realistic images even more challenging. There are also very specific use-cases in a dashboard which a PC does not have to deal with, such as animating a gauge needle – typically 60fps animation is needed to make this look smooth, whereas video games on a PC only need to run at 30fps to look good.

In contrast to the PC arena there are additional challenges concerning power consumption and temperature – some of those challenges are similar to those in the handheld devices.

A key feature of the automotive solution is functional safety which is not required in the computer and handheld markets. At least a part of the information presented in the automotive instrument cluster is considered safety relevant. Presenting wrong information is not acceptable here.

Next: Use Cases

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