Embedded Systems Design Europe - May 2008 - (Page 21)

software ware structure is the software interface, which has three essential components: 1. Microcontroller speciﬁcation (ECU_ HSIS.H). 2. I/O signals interface speciﬁcation (I/O Signal #1, #2, #n). 3. I/O interface macros. (Interface. h, Interface.c) One implementation of the interface layer would be to deﬁne three separate header ﬁles for each of the components. Figure 3 illustrates the partitioning of the software interface layer and how it relates to the overall system. The ecu_hsis.h deﬁnes the low level interfaces to the microcontroller that both the interface and the signal header ﬁle reference. Other microcontroller speciﬁcations are also captured in this header ﬁle such as timing parameters that may be used for example in driving pulse-width-modulated outputs. MICROCONTROLLER INDEPENDENT The signal and interface header ﬁles become microcontroller independent because the ecu_hsis.h ﬁle encapsulates the peripheral level I/O into higher level references through macros. The signal.h ﬁles encapsulates the data further by taking into account the raw sensor speciﬁcation and provide the raw integer signal. The signal.h ﬁle provides a method for interface. h to access sensor independent signal types. The interface.h ﬁle modiﬁes the raw signals that it receives from signal.h by applying the appropriate integer scaling/resolution and zero point offset required for the hardware independent functions. The basis of the interface.h ﬁle is to provide a means of getting data from the real world and putting data out there. Ideally if the microcontroller changes, one would only need to modify the ech_hsis.h ﬁle. If the sensors in the system are changed, only modiﬁcation to the appropriate signal.h ﬁle is required to take into account the new sensor speciﬁcation. By explicitly designing an interface layer that is hardware dependent, the core software layer can be engineered to be hardware independent. Both layers are reusable; the interface layer would be reused on other projects that implement the identical hardware. By design, the core software layer, which is independent of hardware, consists of reusable software modules. The recommendations made in this article are not all encompassing but should be considered as a starting point for software architectures. To provide a guide to developers, more information will be available online in two additional articles in a series. They will provide more details of the structure of the building blocks in this architecture as well as some guidelines to its implementation. Next month, in part 2: we will consider the portable code software structure building blocks. Dinu P. Madau (dmadau@visteon.com) is a software technical fellow with Visteon. He has been developing software for embedded systems for over 22 years. Dinu has developed safety-critical software for anti-lock brakes, vehicle stability control, and suspension controls and is currently working in Advanced Cockpit Electronics and Driver Awareness Systems at Visteon, developing systems leveraging vision and radar technologies. 21 www.embedded.com/europe | embedded systems design europe | MAY 2008 http://www.embedded.com/europe

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Embedded Systems Design Europe - May 2008 Contents Microsoft Provides Embedded Roadmap Enea Buys Developers Irish Start-Up Raises Funds for Telecom FPGAs Kontron Promotes COM Express Nano Mentor Nucleus Platform Provides UI for Atmel Small Form Factor Boards Head for the SUMIT Proffibus Advances IO-Link Integration Embedded Developers Cautious on Multicore Auto Cooperation Improves Test Altera Launches DO-254 Partner Network Building an ‘Instant-Up’ Real-Time Operating Systems An Architecture for Reusable Embedded Systems Software Free up Bandwidth in PCI Express Evaluating Software in Medical Devices Circuit Sensitivity in Analog Circuits Choosing Flash Memory New Products Advertising Contacts

Embedded Systems Design Europe - May 2008

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