Embedded Systems Design Europe - August/September 2008 - (Page 33)

rtos selection This has led to a de-emphasis in benchmarks in RTOS marketing, although they may still be available from vendors on request. A better approach to assessing the likely performance of your application on a given RTOS is to prototype its performance-critical aspects on standard hardware – the vendor should be willing to help with this process. Development tools are an area where different RTOS products vary enormously. Some RTOSs are provided with complete development systems including the compilers and debuggers needed to build the system as well as sophisticated tools for analysing and optimising its behaviour. Conversely, other RTOS products may be shipped purely as source code. While avoiding paying for tools that you are unlikely to use, remember that some rarely-used tools may save a lot of development or debugging effort when you really need them. This can be particularly true of tools that help you to visualise the sequence and timing of events such as interrupts and task switches. Commercial aspects The key commercial aspects can be summarized as: ● initial cost ● on-going costs (royalties, support & maintenance) ● license constraints/ﬂexibility ● market acceptance ● supplier stability/longevity COTS RTOS vendors will generally associate cost with the development tool (IDE), the license or right to develop a product using their RTOS, and sometimes the license to manufacture or deploy their RTOS within your product. COTS vendors place great importance on their IDE, and in the embedded Linux space developers rarely enjoy using an IDE, but instead prefer to develop code using their favourite editor via a command line interface. Royalties are regularly the biggest differentiator between RTOS vendors. The mechanism is simple: the more you use the cheaper it becomes. This www.embedded.com/europe | embedded systems design europe | AUGUST – SEPTEMBER 2008 paradigm extends to some vendors offering their royalty-bearing product ‘royalty free’ through some form of ‘royalty buy-out’. More and more vendors will want you to purchase ‘middleware’. As the name suggests this is the code between the RTOS and the application. This code enables many of the peripheral, network and I/O functions within your software sub-system. These might include: USB stack, TCP/ IP stack or graphics windowing engine. APPROPRIATE LICENCE MODEL Having considered costs, you will also need to decide which licence model is more applicable. Most vendors have a perpetual licence fee. With this model you purchase the development seat up front and pay an annual maintenance fee (typically 20% of original purchase price) which generally entitles you to upgrades and bug ﬁxes. Secondarily, some vendors have an alternative model sometimes referred to as a ‘subscription’ model. With this license model, you effectively ‘rent’ the development seat renewing access on an annual basis. Beneﬁts are lower technology acquisition fees, but cost can escalate after many years. Vendors also have differing types of development seat types. This relate to the manner in which the physical license key is allocated to the installation of the IDE. There are two main types: “node locked” and “ﬂoating” licences. Less commonly, some vendors offer a “unique user license” which is in effect a ﬂoating license associated with a speciﬁc engineer. Nick McNamara is a founder and commerical director of Pebble Bay Consulting (www.pebblebay.com) an independent, privately-owned company that specializes in providing embedded software consultancy and bespoke development services. It was set up in January 2006 and is based in Leamington Spa, England. 33 030-031-032-033_ESDE.indd 33 29/08/08 11:03:21 http://www.pebblebay.com http://www.dvsinc.com http://www.embedded.com/europe

Table of Contents Feed for the Digital Edition of Embedded Systems Design Europe - August/September 2008

Embedded Systems Design Europe - August/September 2008 Contents TI Overhauls DSP Lineup, Adds 15 Processors QNX Publishes Source Code for File System Congatec to Take on Proprietary Market Swiss Multicore Project Wins Microsoft Grant OpenCores Bundles Development Tool ARM Compiler Boosts Freescale i.MX31 LabVIEW Updated for Multicore and Wireless Cover Feature: Interactive Tool Supports Multiprocessor SoC Design Wanted: Benchmaking for Embedded VMM Hypervisors Graphical Design Empowers Spider Robots Building a Power Supply for Discontinuous Transmission Wireless Networks RTOS Selection & Best Practices Achieving Cache Coherence in a MIPS32 Multicore Design New Products Advertising Contacts

Embedded Systems Design Europe - August/September 2008

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