Development tools—hardware, software and reference designs— are playing a crucial role in supporting the embedded designer, as the pressure to get products to market faster mounts. In particular, IDE tools, together with application-specific software libraries and reference designs, are enabling automotive embedded designers to focus on important design details.
The proliferation of electronic control modules (ECMs) in automotive designs is an indication of the complexity and sophistication that make up the embedded electronics systems in a vehicle. Carmakers need to face shorter product development cycles while mindful of the resources they can throw at product development. Development tools —hardware, software and reference designs—play a crucial role in supporting the embedded designer.
Integrated development environment (IDE) tools, with application-specific software libraries and reference designs, enable embedded designers to focus on design details. An IDE (Figure 1) is an integrated toolset for the development of embedded applications. An IDE runs as a 32-bit application on the MS Windows operating system, and includes free software components for fast application development and quick debugging. An IDE also serves as a single, unified graphical user interface for vendor-supplied and third-party software and hardware development tools. In well-designed IDEs, moving between tools is simple because an IDE features a common user interface for all tools.An IDE-based tool component, such as a simulator, can obtain insight into your automotive application. The simulator helps you get started before the development board becomes available. A simulator can perform peripheral simulation and complex stimulus injection and log register values. It helps execute code, and the tool can be exercised with stimulus signals from files, mouse clicks and setup waveforms. The contents of variables and special function registers can be logged onto a file for further analysis. Other components found on an IDE-based tool, such as a device-initializer module, allow peripherals to be set up with a graphical point-and-click method. These tools help developers eliminate programming efforts and enable them to focus on the application at hand. Reference designs
Reference designs provide engineers with a starting point for their project. In most cases, reference designs are not production ready and are intended only as development tools. However, the fundamental concepts of a particular solution are presented within a practical automotive application while preserving the scope for modifications, based on user requirements. Using IDE tools, designers can optimize the reference designs that implement specific auto-related functions, such as anti-pinch windows, tire-pressure monitors, passive keyless-entry systems and electric power-steering systems. Reference designs help designers to quickly complete projects.Since 2000, it is mandatory in the United States for new automobiles to be equipped with a tire pressure monitoring system (TPMS). Some semiconductor vendors supply TPMS reference designs, which can be used for product development and evaluation. Among these reference designs, some use a direct-measurement method to obtain pressure and temperature within a tire. In the direct-measurement method, the pressure is measured inside the tire by the tire pressure sensor module. Measurement is initiated by a low frequency signal sent from the low-frequency initiator module located in the wheel well (Figure 2). The third module, the base station, is the system manager, which maintains the system by scheduling the pressure measurements for each tire and displaying the results to the driver. The base station is capable of distributing this information to other systems via the controller area network (CAN) or local interconnect network (LIN) buses.
A TPMS reference design makes it easy for the manufacturer to customize the solution to meet the specifications. For example, the reference design can be modified to any degree of sophistication, depending on the specification. For instance, using digital sensors and related circuitry, the manufacturer can implement a TPMS that reports the temperature and pressure values from four tire wells to the central processor on the dashboard. This data could be displayed on expensive, elaborate LCD graphics or use low-cost ordinary LEDs. Using a TPMS reference design and an IDE, the manufacturer can evaluate several design options—analog or digital sensors—and remove the low-frequency initiator module (LFIM) to keep costs low.Most TPMS manufacturers prefer to use digital sensors because they don’t need extra calibration, which saves time and effort in TPMS module development. These production-ready TPMS modules can be designed using 8-bit MCUs with varying memory densities. Using an IDE in conjunction with a TPMS reference design makes it easy to implement LIN network communications through a customizable LIN driver that includes all the necessary firmware function modules. The LIN driver saves time and resources by providing the designer a basic structure of the firmware that is needed to implement a LIN network for master and slave nodes, instead of starting from scratch. In addition, a LIN network analyzer tool can be used to monitor the network communications that can be displayed on the PC. The same analyzer tool can emulate the master or the slave node on the network—allowing the designer to debug the nodes without the physical implementation of the network system. The TPMS reference design and IDE combination saves design effort and time.
Consider the case of cell-phone calls in automobiles. Some states and other countries have made it mandatory to use hands-free phone kits. As a result, Bluetooth devices are popular. However, Bluetooth poses design challenges to the developer when used in an automotive application because of ambient noise and acoustic-echo considerations. Without using a reference design, the alternative approach for the designers is to develop the DSP speech algorithms. This is a tough task because each of the speech-related functions is computationally intensive and it is hard to achieve the required real-time performance. Another way is to use application-specific ICs (ASICs) to implement hands-free design—but you cannot fine tune for your application.
To solve this problem, vendors like Microchip provide speech-processing libraries to help shorten the development effort. Running on Microchip’s dsPIC digital signal controllers (DSCs), the acoustic echo cancellation (AEC) library eliminates echo generated in the acoustic path between a speaker and a microphone. AEC libraries are useful in hands-free cell phone kits, in which a speaker and a microphone located in close proximity to each other are susceptible to signals propagating from the speaker to the microphone—resulting in a perceptible and distracting echo effect at the far end. A typical library is compliant with the G.167 standard for acoustic echo cancellation.
In conjunction with AEC, a noise-suppression (NS) software library can work to suppress the effect of noise interfering with speech signals in microphone-based applications, which are troubled by ambient noise captured by the microphone. With the AEC Library, users can achieve up to 50 dB in acoustic echo cancellation. Using the NS Library, users can achieve 10 dB to 20 dB noise reduction, depending on the type of noise (babble, car cabin, white and narrowband noise). Often, AEC and NS libraries are written in assembly language and are optimized to exploit the instruction set and advanced addressing modes found on most DSCs. Designers can call these functions through an application programming interface (API) in their application code and save programming effort. A good reference design can work with any cell phone that has an analog headset jack or supports a Bluetooth headset profile.
Ideally, reference design libraries should be modular, which allows designers to choose modules to set the desired performance levels (Figure 3). Accessories such as an audio cable, headset, oscillators, microphone, speaker, DB9 M/F RS-232 cable and null modem adapter can be used for the evaluation of software speech libraries. If you need to develop a window lift with anti-pinch functionality, you may consider a reference design to fine tune your application. A typical anti-pinch window lift reference design comprises a compact MCU, voltage regulator, relays and drivers, input-conditioning circuitry and network physical layer interface. The signal-conditioning circuitry usually features an H-bridge controller and a 10-bit ADC.
Bidirectional motor control with active feedback for implementing anti-pinch functionality is provided by the coupling of an H-bridge controller with an analog-to-digital converter (ADC). An integrated LIN protocol module enables intersystem communication within the door module as well as the main body controller. Vendors typically make all documentation available on the CD-ROM, including firmware, schematics, Gerber files, assembly diagrams and BOM.
Passive keyless entry automobile access systems need security systems in compact packages at low cost. Relying on a complex non-linear algorithm, a passive keyless entry reference design sends a different and unpredictable code every time. Often, such a reference design comprises three independent boards with unique functionality related to the overall design—the key fob, the base station and the receiver/decoder. The base station starts the RF communication by sending a 125 kHz signal. The key fob receives and decodes the low-frequency challenge from the base station. If there is a match, the key fob will transmit a 432 MHz signal to the receiver/decode. If the receiver/decoder recognizes the key fob, it will send a signal to unlock the door.
PMSM motor control
Due to safety and reliability issues, the latest cars are moving toward deploying permanent magnet synchronous motors (PMSM) in their rotating subsystems. Besides requiring complex drive circuitry, PMSMs require DSC-based
control algorithms, such as field-oriented control (FOC). These advanced motor-control schemes can be developed and debugged using IDE tools. Some vendors offer a data monitor and control interface (DMCI) that integrates with an IDE for projects in which the operational constraints of the motor control can be graphically understood.
DMCI tools (Figure 4) allow you to graphically adjust and plot software variables in motor control applications. They provide slider controls, Boolean (on/off) controls, input controls and graphs (Figure 5). The interface provides project-aware navigation of program symbols (variables) that can be dynamically assigned to any combination of slider, direct input or Boolean controls. The graphs can be configured for viewing program-generated da-ta. A DMCI’s motor control graphical user interface enables users to configure the motor and system parameters for a selected motor. These should include speed, rotation direction, current, heat sink temperature and fault status. These tools support the vendor’s motor control demo boards that help reduce design time. These tools, which run under an IDE, are useful for tweaking software parameters and visualizing data during debug sessions.
An advantage to deploying IDE-based tools in motor control is the practicality of a common design platform, which makes the production of ECMs more efficient. This means automotive module makers have an economical way to offer modules that use PMSM or other motors to employ with sensorless FOC algorithm control. DMCI tools make fine tuning motor control easy, allowing designers to port their algorithms across a variety of motor platforms, including PMSM, brushless dc, brushed dc and ac induction motors.
With these high-end development efforts, the security of firm-ware intellectual property (IP) is another issue for auto manufacturers who use IP components that are developed across many countries.
Designers can expect changes in environmental standards to continue to drive advanced motor-control techniques for creating energy-efficient modules.
Using IDE tools, designers can optimize the reference designs that implement specific auto-related functions. With a consistent user interface for multiple hardware and software components, IDE tools enable designers to develop and debug subsystems that make up the car. These tools enhance designer productivity by allowing designers to work on projects—correlating information throughout the development process, and through the optimization and programming phases.
ABOUT THE AUTHORSJin Xu is an applications engineer with Microchip Technology’s Automotive Products Group.Priyabrata Sinha is principal applications engineer, Digital Signal Controller Division, Microchip Technology Inc.
Jorge Zambada is a senior applications engineer, Digital Signal Controller Division, Microchip Technology Inc.