As embedded systems continue to expand, so does the complexity of the system. Therefore, the realization of user graphics (GUI) in the embedded system has become the trend of the times. In the measuring instrument, the graphical interface is also widely used, one is embedded in the operating system, most of the user graphical interface (GUI) is supported by the operating system (such as OS, WinCE, Linix), call the system Kind of API function implementation. These operating systems provide a large number of library functions for implementing GUIs, and also provide programmers with a good platform for interface design. However, this embedded technology has high hardware requirements, which is equivalent to embedding a computer. For example, using WinCE, it is very convenient to design a Windows-style graphical interface. The other is to develop small systems directly using DSP technology. This system is streamlined, has low hardware requirements, but has a relatively simple function. Its user graphical interface (GUI) is developed on the basis of VisualDSP++ 4.0 Kernel, and the interface style is closely related to the function of the instrument. On the basis of the completion of the instrument's waveform and menu display, the team also made some general user graphical interfaces, such as file manager. Of course, the user graphical interface designed is far less powerful than WinCE, but it is convenient enough for the user of the instrument - because this is the graphical user interface of the instrument. Not a graphical user interface for handheld PDAs.
User interface implementation principle
The implementation of the user's graphical interface requires hardware and software support. Through the deployment of the operation platform, the display program is called, the display program refreshes the display buffer, and then the display driver displays the contents of the display buffer on the LCD screen.
The following is a brief introduction to the main components.
GUI graphics standard library
In order to display various graphics and patterns on the user's graphical interface, in addition to the support of hardware circuits, powerful software support is required. Among them, the (GUI) graphics standard library is the most basic and indispensable. The graphical standard library of the user graphical interface (GUI) includes the most basic drawing points, drawing lines, drawing rectangles, filling rectangles, drawing circles, placing patterns in bmp format, displaying Chinese and English functions, etc. The more powerful the graphic library function is, The more you can support a complex user graphical interface (GUI).
GUI operating platform support
Just having a graphical standard library for drawing graphics, it is not enough to implement a graphical user interface. The graphics library is indispensable for a single screen, but to form an organic, operational user graphical interface, you also need a stable, powerful operating system platform in the background.
The operating platform determines the state of the next system according to the user's external input (usually the keyboard) and the current state of the system, thereby calling the corresponding GUI interface. In this way, a graphical user interface is implemented.
Implementing graphical hardware principles
RIGOL DS1000 series digital oscilloscope adopts 320×234 resolution TFT liquid crystal display. Through the liquid crystal driving circuit, the liquid crystal can be normally displayed. Through frame signal synchronization, line signal synchronization, data signal clock synchronization, display point The array data will be written from the SDRAM into the display buffer of the liquid crystal display to display a color image.
Design Ideas of User Graphical Interface (GUI) Software
Division of interface types
The design of the user's graphical interface (GUI) cannot be completed simply and uniformly, taking into account the user's operating interface in various situations. Based on the commonalities of these interfaces, we divide these interfaces into the following categories, and the same type of interfaces will have the same or similar functional areas. Each interface will have a corresponding handler and a special data structure.
According to the different functions implemented, the following interface types are divided:
A. Background grid display interface; B. Waveform display interface; C. Help document browsing interface; D. Menu display interface; E. File management browser interface; F. File name input interface; J. Prospect content display interface (including Various parameters display information, measurement information, and prompt information, etc.).
Interaction between interface area and external input
As can be seen from the above, although the displayed graphics are various, they can all be abstracted into a certain data structure having common attributes. The data structure is like the soul of the graphical interface. If you master the data structure, you can change the graphical interface.
So how to design, control, and change these data structures becomes the key to implementing the user's graphical interface (GUI). In order to respond to the input of external users, we need to develop a set of mechanism operation rules, and this mechanism is the system status machine, which is also the operation platform that the user uses to operate the instrument. According to this set of operating rules, our system changes the data structure used under various interfaces according to external input, thus realizing the user's operation on the graphical interface.
Of course, in the actual design, the operating platform not only changes the data structure of the GUI, but also considers the task scheduling and the change of the data structure in other task modules.
Software design flow for user graphical interface (GUI) of digital oscilloscope
Designing a good user graphical interface is a huge and detailed project. It involves all aspects of the interrelationship and also involves many details of the implementation process.
How to sort out these many changes and relationships is the key to design. The RIGOL team used some global variables as flags in various states and modes to change the user's graphical interface. However, because of the large number of variables, the possibility of collocation between variables is multiplied, and the state transition relationship is multiplied. This is not so much for programmers as programming, but rather an extremely complex logical combination.
Therefore, such an idea is theoretically feasible, but it is not desirable in practice. We should try our best to find the variables or structures that can penetrate the entire system, mark different states and patterns. Finally, we use the keyboard's input key value as the main line, supplemented by various global variables to control the system state changes. Although there are many key values, because only such a variable is used as a state quantity, the system state changes can be in control. So, in this system, the key variable KEY_ID becomes the protagonist and the user interface will change around it.
The key value variable KEY_ID is changed according to the user's input. This does not describe how state variables are transferred. We describe how the user's graphical interface output is completed for the given key-value variable KEY_ID.
Conclusion
At present, domestic digital oscilloscopes, in addition to the low performance index of the measurement signal, are not as well considered in foreign products in terms of system integrity and user operability.
In order to make up for the shortcomings of domestic products in this respect, the DS1000 series digital oscilloscope developed by RIGOL development team not only realizes high memory depth and high measurement accuracy, but also pays attention to the design of graphical user interface. Continue to maintain its technological innovation and humanization, localization advantages, the new user graphical interface makes it easier for users to measure and analyze waveforms than ever before.
As the functionality of the instrument increases, higher requirements are placed on the user's graphical interface (GUI), which requires the GUI to be more systematic, modular, and functional. So there is still a lot of work to be done in this area.
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