<p>There are many experts tackling the coexistence issue so that consumers can have Bluetooth and WLAN connectivity in their laptops and smart phones. The challenge remains to make these technologies transparent to the user. The solutions need to be simple, reliable and unobtrusive to the device's primary application. </p>

Performance: Boot time reduction In many cases, a fast boot up is more than a nice-to-have feature. There can be operator or even governmental regulations that require an emergency call be made within just a few seconds. One obvious approach is to postpone loading the drivers or other run-time software until later in the execution cycle.

The developer needs to be aware of the interdependencies of the software being loaded at boot time. For example, it may be a requirement to have a splash screen” appear very early in the booting process. But the splash screen image resides in the flash file system.

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Therefore the drivers for the flash filesystem must be loaded first enabling access which in turn allows the splash screen to be read and loaded into display memory. The final optimization results can be impressive with calls placed within 10 seconds from power on”—more than two times faster than phones from Symbian or Microsoft.

Size: Integrated support for ARM Thumb” instruction setFor ARM-based mobile devices (a sizeable percentage of devices), there is a special instruction set optionally available called Thumb. This additional mode of execution on the ARM processor is specifically designed to support very compact code generation by compliers.

The technology touches both the toolchain, since the compiler needs to make use of the Thumb mode capability in generating code, as well as the Linux kernel, which needs to properly save and restore the state of applications running Thumb instructions.

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Stack frame layout, register usage, and calling sequences need to support the Thumb capability as well. Closely tied to the complier is the run-time library, and in the case of ARM, uClibc, which is a compact version of the gnu toolchain's run-time library glibc, is complied using the Thumb mode capability.

In addition, a comprehensive set of run-time packages is also supplied having been built under the Thumb mode. All of these enhancements contribute to a reduction in the memory footprint required to run Linux and its applications.Size: Execute in placeRAM is a system resource that is always in short supply on mobile devices. The amount of RAM contributes directly to the cost or bill of materials (BOM) and the absolute amount of RAM can also negatively affect the battery life.

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In general, Flash memory is cheaper (although considerably slower) than RAM, making the increasing utilization of Flash memory a preferred goal. With the traditional Linux approach applications are loaded into RAM from the filesystem and then executed from RAM.

In classic embedded systems the application was stored in a sort of read-only memory (EEPROM, ROM, etc.) which was part of the processor's memory address space. As long as the application was written to be executed from ROM, this approach saved RAM.

The completed harness design sometimes also has to cross organizational boundaries, for example as a return data feed to the OEM customer or to subcontract manufacturers. An ability to transfer data electronically and to reuse it in other systems is clearly highly desirable.

Part 4 of this series discusses new generation COTS harness design tools to ease the seven pain points” noted above.

Mark Colonnese is a product marketing specialist for Mentor Graphics Integrated Electrical Systems Division. With 10 years experience in the software industry working with many OEM and Tier 1 harness suppliers, Mark has responsibility for the Capital HarnessXC harness design tool that complements Mentor's CHS electrical design solution.

Part 1 of this series dealt with overall wiring system design as providing the critical foundation for the growth in automotive electronics systems and functionality. In that installment we looked at how to develop a set of system diagrams into a specific vehicle architecture, taking into account the complexity of a modern vehicle (both in terms of components and the option/variant complexity arriving from increased customer choice).

Part 2 looked at simulation and analysis techniques that can be applied to an electrical distribution design flow to make it more efficient and less costly.


In the next article we will discuss these approaches and the advantages and trade-offs of each.

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