Digital signal processing with Virtex-II Pro FPGAs from Xilinx enables a wide range of sophisticated electronics designed to make driving safer.

According to a study carried out by Visteon Corporation, safety is the number one concern of vehicle customers. It’s at the heart of the consumer priority hierarchy (Figure 1).

Increasingly, equipment designers are turning to programmable technology to make cars – and driving – safer. Far beyond the more familiar tire and braking technology, side impact protection, and airbags, today’s “driver assistance” systems have evolved from the physical to the electronic domain. The latest electronics-rich vehicles use sensors to continuously evaluate surroundings, display relevant information, and in some instances, even take control of the vehicle.

Safer, More Efficient – and More Comfortable

Driver assistance systems can offer basic safety features, such as adding infrared (IR) cameras to improve visibility, but the more advanced equipment can warn the driver of potentially dangerous situations. Using a wider array of sensors, these electronic systems enable the vehicle to be aware of surrounding traffic, lane direction, and potential collisions. The ultimate aim is to enable the vehicle to react automatically – whether this involves giving the driver information or assisting with car control – so that occupants are kept safe.

For example, some of the latest trucks are equipped with video cameras that capture images of the lane ahead. If the vehicle changes lanes without using indicators – a sign, perhaps, that the driver is fatigued – an alert is sounded through the cabin loudspeakers.

Driver assistance can also make drivers more comfortable by automating routine actions. Conventional cruise control, for example, has now evolved into adaptive cruise control (ACC), which automatically controls the throttle. ACC brakes to match the speed of the vehicle in front and keep a safe distance from it. If the vehicle ahead accelerates or changes lanes, ACC returns to the pre-set speed of the cruise control.

Other new developments may also serve to make traffic more efficient. The “electronic tow bar,” for example, will enable truck convoys in which the lead vehicle is driven manually and the following trucks are driven automatically. In addition to taking some of the burden from drivers, the distance between trucks can be greatly reduced because the electronic driving device reacts faster than a human. Not only does this save valuable road space, but by traveling in the slip-stream of the vehicle in front it saves fuel as well.

Xilinx FPGAs in Driver Assistance Systems

A driver assistance system is partitioned into very high-speed input processing and relatively low-speed sensor inputs and output control signals, each under the control of its own processor (a Xilinx MicroBlaze™ 32-bit soft processor, for example, or even an embedded IBM PowerPC™ in a Virtex-II Pro™ FPGA, Figure 2).

The high-speed section is dedicated to the real-time processing of video coming from the cameras mounted at the front of the vehicle. Given the critical nature of the application – crash avoidance, emergency procedures, and alerts – real-time processing is absolutely essential. Typically, two or more cameras will be used to capture a stereo image, thus enabling calculation of image depth (directly related to real distances from objects) in the FPGA. This information, combined with radar and laser measurements, plus the information collected from gyros and wheel sensors to detect motion, yields a very accurate map of the vehicle’s surroundings and its path.

Capturing and processing this information in real time requires the use of math-intensive digital signal processing (DSP) algorithms. Software processing cannot meet these performance requirements, and it often takes several conventional DSP processors to perform such high-speed tasks. Frequently, even ASSP (application-specific standard product) video processors cannot match the extremely high-speed DSP performance of Xilinx FPGAs, also known as XtremeDSP™ processing.

In addition, using fully flexible FPGAs rather than off-the-shelf video components enables equipment manufacturers to easily develop the unique, optimized edge detection, image depth, and enhancement algorithms that will differentiate system performance from the competition.

After processing the video, the decision tree mechanisms can be partitioned between hardware (for speed-critical algorithms such as sudden object avoidance) and processor software (for sounding alerts such as lane drift warnings). Partitioning speed-critical processes into FPGA hardware also enables testing at real-time rates, something that is impossible to do in software.

XtremeDSP – Real-Time Image Processing

So why can Xilinx FPGAs offer faster video processing than conventional DSPs? The fundamental reason has to do with the FPGA architecture’s inherent ability to process data in parallel. In contrast, a DSP processor takes in successive instructions and data, and processes them in a serial fashion.

In addition, the latest Virtex-II Pro family of devices from Xilinx also has an array of embedded, high-performance multiplier blocks to increase image-processing power even further. This enables the FPGA to be configured as a large array of multiply-accumulate (MAC) engines performing multiple operations concurrently (in a single clock cycle) as opposed to multiple cycles through the single or few MAC engines available in conventional DSPs (Figure 3).

Another advantage of Xilinx FPGAs is that you can size the array precisely to suit the calculation requirements, which is ideal for performing calculations on images. Calculations can be performed on clusters of pixels, such as discrete cosine transform (DCT) macroblocks, concurrently with other blocks in the picture instead of having to scan the entire picture sequentially. And because processing can now be done in real time, less memory is needed for buffering pixel values when using FPGAs.

In addition to real-time performance, the reprogrammability of Xilinx FPGAs also offers superb system flexibility, enabling algorithm upgrades even after deployment. This is important, as current driver support systems are still in the early stages of research and development. As edge- and object-detection algorithms improve over time, hardware upgrades can be accomplished in a matter of minutes and with no board redesign.

Bridging Automotive Networks

Today, multiple network technologies have emerged that cover various functions and features in the car. These technologies range from multimedia networks, such as media oriented systems transport (MOST) in the cockpit, to car control networks like FlexRay™ automotive control systems. As vehicles evolve into a truly networked arena, equipment manufacturers must determine which standard will be the most successful or offer the greatest advantage over other network protocols.

However, one of the real benefits of using an FPGA rather than an ASSP is that it allows you to produce designs that precisely match interfaces and peripherals to the system requirements – particularly useful when trying to interface with protocols in the early stages of development. When you’re trying to get a product to market quickly, a chipset or ASIC (application specific integrated circuit) re-spin is both costly and time-consuming.

With an FPGA, if the specification of a network protocol changes during a standard’s early days, all it takes to support the latest revision is a relatively simple redesign in software and a download of the new hardware configuration. You can even do it over a wide area network using Xilinx IRL™ (Internet Reconfigurable Logic) technology, which means the hardware can be revised during maintenance without costly recalls or extra manpower.

IQ Solutions for Automotive Applications

To address the needs of automotive electronics equipment designers, Xilinx has created a new range of devices with an extended industrial temperature range option. Called the “IQ” range (Table 1), it comprises current Xilinx industrial grade (I) FPGAs and CPLDs qualified to a new extended temperature grade (Q).

Table 1 - Temperatures supported by Xilinx products

	Temperature Grade/Range °C
Product	C	I	Q
FPGA	TJ = 0 to +85	TJ = -40 to +100	TJ = -40 to +125
CPLD	TA = 0 to +70	TA = -40 to +85	TA = -40 to +125

The first products qualified to operate at the new temperature grade are Spartan™-XL 3.3V FPGAs ranging from 5K gates to 30K gates, and the 36 and 72 macrocell XC9500XL 3.3V CPLDs. In the coming months, the IQ family will be expanded to include FPGA devices up to 300K gates, and CPLDs up to 512 macrocells in density (Table 2).

Table 2 - Xilinx IQ solutions silicon for automotive applications

Xilinx IQ Solutions Silicon Selector
Product Family	Packages	Voltage	Density Range
XC9500XL CPLDs	VQ44, VQ64, TQ100	3.3V	36 - 72 Macrocells
CoolRunner XPLA3 CPLD	VQ44, VQ100, TQ144, PQ208	3.3V	32 - 512 Macrocells
CoolRunner-II CPLD	VQ44, VQ100, TQ144, PQ208	1.8V	32- 512 Macrocells
Spartan-XL FPGA	VQ100, TQ144, PQ208, BG256	3.3V	5K - 40K Gates
Spartan-II FPGA	TQ144, PQ208, FG256	2.5V	15K - 200K Gates
Spartan-IIE FGPA	TQ144, PQ208, FT256, FG456	1.8V	50K - 300K Gates

Conclusion

The new wave of driver assistance systems requires high-performance image processing without sacrificing flexibility, especially during early stages of research and development of object detection and automotive network technologies. The use of Xilinx FPGAs at the heart of such systems offers the industry’s best DSP performance, unrivaled support for network connectivity standards, and gives system architects a fully flexible design platform with which to work. Working in real time, these systems provide emergency driver alerts, assist car control, and significantly increase safety.

Further Information
www.xilinx.com/esp/technologies/consumer/automotive.htm	Xilinx Emerging Standards and Protocols (eSP)
www.xilinx.com/automotive	Xilinx Automotive Products – The IQ Range
www.xilinx.com/dsp	Xilinx DSP Central
www.xilinx.com/products/logicore/coredocs.htm#DSP	Xilinx DSP Core Solutions Documents
www.xilinx.com/ipcenter	Xilinx IP and Core Solutions Catalog
www.visteon.com	Visteon Corporation Home Page

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