Linux is quickly transforming into a top-notch embedded-systems development and deployment platform. New tools from a variety of vendors are letting designers deploy it in a range of environments, from those that require a small memory footprint to those that need real-time support.
Even with Linux as a common base, users have to examine the fine details in these tools to identify their differences since they're made by different companies. In most cases, developers have the advantage of moving from one product to another without major redesign. These tools include Monta Vista's Hard Hat Linux CDK 1.2, LynuxWorks' Blue Cat 2.0, Lineo's Embedix SDK for X86, and FSM Labs' RTLinux 3.0.
Hard Hat Linux can fit into 500 kbytes of ROM or flash memory plus 800 kbytes of RAM. Command-line configuration utilities have a graphical counterpart in the latest release. It comes with a variety of add-ons, including the hard real-time RT Scheduler, the Microwindows GUI, and a PCI backplane networking system known as Hard Hat Net.
The Hard Hat Linux remote debugging tools are based on gdb. They offer source kernel-level debugging that will work with polled Ethernet in addition to a serial connection. Monta Vista also supports the public ViewML compact web browser, which uses Microwindows. Hard Hat Linux is available for the x86, PowerPC (including PowerQUICC), StrongARM, and NEC MIPS.
Blue Cat 2.0 comes with two proprietary command-line tools, known as krootfs and mkboot, for creating embedded file systems and bootable images. These tools may not have a friendly interface, but their numerous options allow extensive modifications to images. They also use the popular RPMpackage files. Blue Cat ships with over 20 prebuilt kernel images.
Blue Cat includes remote debugging tools. Kernel-level debugging support operates over a serial connection. Application debugging can be performed using a serial or TCP/IP connection. A run-time memory-sizing application also is included, along with a binary version of LynuxWorks' testing suites for its evaluation boards.
Also, LynuxWorks creates version-stabilized images that use a common code base for all supported microprocessors. This can be important when deploying common applications in heterogeneous networked environments. Long-term deployment support contracts of up to 15 years are available. The development tools can be hosted on RedHat Linux or TurboLinux Workstation. Blue Cat is available for the x86, PowerPC, and PowerQUICC II architectures.
Embedix SDK for X86 includes a complete distribution of Caldera Systems' OpenLinux, along with the Embedix Target Wizard (see the figure). This graphical application constructs an embedded Linux image for bootable media or for FTP transfers. The Builder tool supports RPMs. The Builder's Library Reduction tool automatically constructs new, smaller libraries containing only the support needed for an application.
The Embedix SDK for X86's hierarchical database manager tracks Embedix Component Description files and State Definition files that describe an embedded project, including fulfillment requirements and disk sizes. Typical Embedix Linux requirements start at 4 Mbytes of RAM and 2 Mbytes of ROM or flash memory.
FSM Labs supplies commercial support for RTLinux. The noncommercial version is available at www.rtlinux.org. RTLinux provides real-time support that can be employed in most Linux distributions, from standard to embedded Linux distributions.
The latest version supports SMP x86 platforms and uniprocessor versions for x86, PowerPC, and Alpha. Improvements include spinlock mutexes, mutex priority ceiling support, a signal interface for real-time interrupts, an updated mbuff driver, and Usleep support. The x86 SMP implementation permits IRQ assignment to specific CPUs. It's also possible to mix v1 and v2 APIs.
The new embedded Linux offerings have some interesting competition. QNX Software Systems has added a Linux front end to its QNX Neutrino operating system. From an application's perspective, QNX Neutrino looks and acts like Linux. QNX tools are now available for free, but there is a run-time royalty charge. This approach isn't unique, though. LynuxWorks' LynxOS uses the same technique and a similar licensing structure.
Two popular sources of information are ZDNet's LinuxDevices.com and the Embedded Linux Consortium's (ELC) web sites. For more information about embedded Linux, visit www.linuxdevices.com, www.rtlinux.org, the Embedded Linux Consortium at www.embedded-linux.org, Monta Vista at www.mvista.com, FSM Labs at www.fsmlabs.com, QNX Software Systems at www.qnx.com, LynuxWorks at www.linuxworks.com, and Lineo at www.lineo.com. For details about the ViewML browser, try www.viewml.com.