Data Visualization for Software Development Tools

Transcription

1 Data Visualization for Software Development Tools Author, David Leal Document Number: DTAVSUALZIONWP Rev. 0 11/2005

2 Understanding application behavior through raw data output (such as memory, register views) from debuggers can be a daunting task for software developers. Determining trends or developing a suitable set of stimuli to the system under test can be difficult. Visual synthesis of the same raw data output makes data analysis quicker and easier, conveys data changes faster and makes stimulating the system more intuitive. CONTENTS 1. Motivation Theory Visualization in Software Applications Data Visualization Example Summary Freescale...8

3 1. Motivation Developers programming in C++, C and assembly often drown in data. Advances in computing technology and hardware are making software development applications, which harness these powerful hardware platforms, more complex. This complexity is often compounded by the amount of data that can be acquired or generated by these advanced software programs. Application developers need to get their arms around this enormous amount of information. Depicting a complex, multilayered project accurately and quickly is a challenging task. When debugging complex code at the object, function, assembly or even machine level, it is difficult to pour over seemingly endless pages of code presented in a non-intuitive manner. Leveraging vision into a key component in debugging applications can mitigate this problem. To achieve this, an accurate representation showing multilevel hierarchies, relationships between objects and modules, and system component specifications, needs to be modeled in a user-friendly, visual environment. This situation demands data visualization tools. Data visualization can make existing tools more effective by conveying data faster, allowing users to see changes in the data more readily, and stimulating the system under test. 2. Theory The power of computers to collect, store and manipulate numbers has increased dramatically since Richard Hamming's observation in 1962 that the purpose of computing is insight, not numbers. During the late 1970s and 1980s, advances in computing power and network bandwidth delivered high-performance computing from the mainframe nearer to the desktop. This allowed movement from the original model of batch processing to a model more closely tied to the desktop environment. In the original batch processing model a centralized supercomputer produced images from predefined viewpoints that were then saved to disk or video for later viewing. A more current model defines a more interactive approach where image rendering is handled at the desktop level and the developer is able to interact with the simulation in near-to-real time. With this increase in computing performance and the advances in both hardware and software for computer graphics, the resources were available to begin considering visualization of scientific data. Much of this increased power, however, is wasted because humans are poor at gaining insight from data presented in numerical form. As a result, visualization research and applications take on great significance, offering a promising technology for transforming an indigestible mass of numbers into a medium that humans can understand, interpret and explore. The transformation from numbers to insight requires two stages. The first stage maps from numbers (data/processes) to images by means of some algorithmic technique. The second stage maps from images to insight by means of perception, which includes recognition and interpretation. A true science of visualization must incorporate both a formal theory of computer graphics and a theory of human perception. The construction of visualization tools must take into account the viewer's goals and purposes. In choosing variables to represent different data components, for example, it is necessary to know what level of perceptual organization needs to be supported. This, in turn, depends on the kind of judgments that the user wants to make. Design of visualization is partly a knowledge engineering problem. Data visualization in software development tools is a natural progression of the application of this technology due to the enormous amounts of data presented in a non-intuitive format in current debugging tools. Data Visualization for Software Development Tools, Rev. 0 3

4 3. Visualization In Software Applications The concept of visualization is not limited to a passive tool (displaying data in a human readable form), but can also be leveraged to provide stimuli into an environment. While data visualization is usually thought of in terms of graphs and charts used by humans to process information, the same concept can be extended to generate input values for a system, which act as stimuli for an application (as shown in Figure 1). Furthermore, a visualization tool does not need to be restricted to application data input/output; it can be extended to control the whole development or debugging process. For example, complex debugging tasks can be visualized using special custom controls embedded into the visualization environment. With such an extended view, visualization means a completely different view of the data and the behavior of an embedded application, which allows the developer to understand the data faster and more thoroughly. Data Image Application FIGURE 1 An example of a visualization application is the visualization of a car taillight, shown in Figure 2, using a Freescale CodeWarrior tool set. Buttons are used to stimulate the application (e.g., to set the flasher bit) and, at the same time, visualization is used to give feedback on the current bit sets, as well as to visualize the complete system behavior. FIGURE 2 Thus, visualization is extended into a more complete role, including testing and prototyping through simulation. This is a significant improvement from the case where the same model is analyzed without such visualization features. Without these advanced features, debugging tools would be limited either to an operating system level, as shown in Figure 3, or to an even lower variable display level. Although Figure 3 offers a good view of the system, it is at a lower level and, therefore, less intuitive. A combination of high-level visualization, as shown in Figure 2, with a deep, detailed view of the system internals, as in Figure 3, serves as a very powerful tool and improves developer productivity in most environments. 4 Data Visualization for Software Development Tools, Rev. 0

5 FIGURE 3. VIEW OF OSEKTURBO OS OBJECT INSPECTOR 4. Data Visualization Example Consider a more detailed example of an application for the HC908QT4 processor that uses a potentiometer and an LED, as shown in Figure 4. The potentiometer acts as a representation of any analog data, such as water level in a tank or perhaps the temperature of a thermometer. The LED acts as a device that gives feedback to the developer. In this application, it is in the OFF state for low values, in the ON state for high values and in the BLINKING state for mid-range values. Threshold voltages are set at one-third and two-thirds of the maximum voltage. Vc Vc Vc Vd HC908QT AD PortA Vs FIGURE 4 Control After creating a project (in Freescale CodeWarrior Development Studio for HC(S)08 Microcontrollers) and choosing the target board, which in this case is the Freescale HC908QT4 board, the user generates the initialization code and low-level drivers for the application. (Note: in Freescale CodeWarrior products, the Project Manager generates the code automatically.) The next step involves developing the application code for the example. In the Project Manager, the Main and other procedures can be added to MyQT4project.mcp, as shown in Figure 5. The example code used to implement the application in this system is shown in Figure 6. From this step forward, data visualization plays a key role in viewing the input and output of the application, as well as in debugging the application. FIGURE 5 Data Visualization for Software Development Tools, Rev. 0 5

6 static byte myvalues[1]; /* Number of channels */ void main(void) { byte min = 255/3; byte max = (255*2)/3; byte err; bool s; int i; for(;;) { err = AD1_Measure(TRUE); /* run measurement with set wait for result */ err = AD1_GetValue((byte *)myvalues); /* Get results */ if (myvalues[0] > max) { /* Compare value and action LED */ s = 1; } /* set LED ON */ else { if (myvalues[0] < min) { s = 0; } /* set LED OFF */ else { s = s^1; } /* invert LED ON <-> OFF */ } for (i = 0; i < 5000; i++); /* delay */ Bit1_PutVal(s); } } FIGURE 6 Launching the debugger brings up several windows including the source window, shown in Figure 7, and the data window, shown in Figure 8. Other windows include the assembly window and the register window. Collectively, these windows allow the developer to see the C source code (as well as macro assembly and C++), the disassembled instructions, the contents of registers and the values assigned to variables. The memory window, shown in Figure 9, displays bytes of memory and tracks changes in different colors, allowing direct editing of the memory contents. FIGURE 7 FIGURE 8 6 Data Visualization for Software Development Tools, Rev. 0

7 While these features and tools make the development and testing of an application faster, the popular method of testing a series of inputs is setting the input variables to a particular value, running the code, observing the output and then repeating this process. With this method, there is no viable way in which the developer can gain the ability to stimulate an analog input in real-time. Data visualization changes this by providing the developer with the ability to stimulate built-in analog and digital inputs as well as display the status of the outputs, all in real-time. After opening the Visualization Tool from the component window, shown in Figure 9, the developer adds components in the visualization window, shown in Figure 10, such as the potentiometer for our example. FIGURE 9 The properties of the potentiometer, shown as a box, are specified, including the port to which it is assigned, color and the scale. To verify the stimulation, the update rate is specified so that the window is automatically refreshed to show changes in the values. The red column of the data stimulation is dragged up and down to change the resistance of the circuit and the output is viewed in the memory window instantly. The changes to the output appear in red as shown in Figure 10. At this point the developer has implemented the very powerful ability to stimulate an analog input in real-time. By simply adding an LED, as shown in Figure 11, the actions the processor is programmed to take when the application code is running are shown. The LED properties are adjusted to have the preferred visual properties, as well as the port to which it is connected. The LED is also set to refresh periodically to reflect the values of the outputs. The potentiometer and the LED are connected to the same pins as the final application. This simple addition represents the powerful ability to display the output of a peripheral device and reverse the function to stimulate the pin, if needed. FIGURE 10 In the free-running case of this example, the potentiometer is dragged to different positions, changing the inputs of the application and, thus, the outputs as demonstrated by the different colors of the LED. In this example, the bottom third of the potentiometer leads to a gray LED, the middle third makes the LED blink, and the top third leads to a yellow LED. It is worthwhile to note that, without data visualization, developers remain confined to the cumbersome process of modifying input variables, running the program and observing the output for each run of the application. Data visualization provides a more user-friendly way to display the activity of a system under test in real time. FIGURE 11 Data Visualization for Software Development Tools, Rev. 0 7

8 5. Summary Data visualization can make existing software development tools more effective by conveying data faster and allowing developers to see changes in the data more readily. Features in software development tools such as data visualization and I/O simulation allow developers to create conditions as close to the real environment as possible. Ultimately, data visualization speeds up development time by helping the developer spend less time on details and concentrate his or her energy on higher-level issues. 6. Freescale Data visualization, I/O simulation and I/O stimulation and debugging environment controlling capabilities and features can be found in the following Freescale products: CodeWarrior Development Tools for: > Freescale HC08 > Freescale HC12 > Freescale MPC5500 > STMicroelectronics ST7/ST19 References > Green, Marc. Toward a Perceptual Science of Multidimensional Data Visualization, > Hamming, R. Numerical Methods for Scientists and Engineers, > Joffrain, Chris. CodeWarrior Development Tools for 68HC08 and HC12 Microcontrollers, > NetViz Corporation. A New Approach to Information Visualization and System Modeling, > Styger, Erich. Metrowerks Engineering, Data Visualization for Software Development Tools, Rev. 0

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