Embedded multi-function controller 0P7200 and its application

In recent years, the automatic test system of electronic equipment has entered a new era with miniaturization, intelligence, integration and informatization as the development direction, while taking into account the requirements of practicality, reliability and economy. 0P7200 is a new embedded multi-function controller. It has the advantages of high reliability, small size, economy and practicality. It meets the requirements of portable test systems. At the same time, it has an Ethernet interface, which is convenient for the establishment of large-scale distributed measurement and control systems. Taking the application of 0P7200 in the automatic test system of transponders as an example, the interface application and software development of 0P7200 are introduced in detail. The system uses the rich interfaces of 0P7200 to simplify the overall design, and simplifies the test operation and improves the test efficiency by using a touch screen.

1 Introduction to 0P7200 Multi-function Controller

1.1 Appearance

0P7200 has 9 membrane keys, 1/4 VGA (320×240 pixels) white backlight LCD with programmable switch and 4 096×4 096 analog touch screen, as shown in Figure 1. 0P7200 has a size of 144 mm×112 mm×43 mm, has passed CE certification, and can work stably in harsh working environments.

1.2 Internal structure

The core of 0P7200 multi-function controller is Rabbit 2000 microprocessor, which uses CPLD as decoding unit and expands off-chip Flash memory and SRAM memory. In terms of interface, microprocessor Rabbit 2000 directly controls RS485, RS232, Ethernet and other interfaces, and CPLD can be used to control other interfaces, such as digital input/output interface, analog-to-digital conversion control interface, LCD display control interface, keyboard control interface, touch screen control interface, etc. Its internal structure is shown in Figure 2.

1.3 Pin Function Description

The pin configuration of 0P7200 is shown in Figure 3, and the functions of each pin are described as follows: 1) 19 switch input channels, with an input voltage range of ±36 V and overvoltage protection; 2) 8 switch output channels, each of which can be configured separately by software, and each channel can output a maximum voltage of 40V and a current of 350 mA when active, a maximum output voltage of 40 V and a current of 250 mA when passive, and a maximum output voltage of 40 V in tri-state; 3) Analog acquisition channel, providing 8 analog input channels with 11-bit resolution for single-ended input, and 4 analog input channels with 12-bit resolution for differential input, and the input signal can be set by software. There are 8 options in the range of 0 to 20.0 V for single-ended input, and 8 options in the range of 0 to ±20.0 V for differential input; 4) 10Base T Ethernet interface with RJ-45 interface; 5) 3 serial ports, including 1 RS485 interface and 2 3-wire RS232 interfaces; 6) Reset pin, low level is effective; 7) 2 external power supply interfaces, which can use 9-40 V DC power supply or 24 V AC power supply, and have internal voltage stabilization circuit. At the same time, OP7200 has a replaceable 3 V coin-type lithium battery inside to maintain the real-time clock and SRAM.

1.4 Software Development Environment

OP7200 is programmed using Z-World's industrial-grade Dynamic C (or dynamic C) software development platform, which is a development system for writing embedded application software, designed specifically for Z-World controllers and Rabbit microprocessor-based controllers.

The Dynamic C development platform integrates functions such as editing, compiling, linking, loading and debugging. It also comes with many function libraries to support real-time programming, chip-level I/O, international characters, bitmap images, and the display of graphic structures such as circles, lines, and rectangles. It also has the following functions: 1) Function string, which is a concept unique to Dynamic C. It allows special code blocks to be included in one or more functions. When the program executes to the specified function string, all the code blocks in the string will be executed. Function string supports requests for software initialization, data recovery, and other tasks; 2) Interconnection statements, which can simulate multiple concurrent events in one program; 3) Public functions, which allow collaborative events to be simulated in one program; 4) Partial declarations support preemptive events in a single program; 5) Interrupt keywords allow programmers to use standard C to write interrupt service programs; 6) Shared and protected keywords, which are mainly used to share protected data in different areas or store them in battery-powered memory; 7) One of the features of Dynamic C, allowing programmers to maximize the use of extended memory.

Dynamic C also supports cooperative multitasking and preemptive multitasking. Cooperative multitasking is a method of executing multiple different tasks at the same time. When there is no immediate task to execute, each individual task will automatically comply with its running time. Preemptive multitasking is a method of giving priority to tasks with higher priority. Generally, the program uses interrupts to force the execution of tasks with higher priority. [page]

2 Application of 0P7200 in Transponder Automatic Test System

The airborne transponder (referred to as transponder) for air traffic control is an important airborne navigation device. It works with the ground secondary radar to provide the air traffic control system with various information of the transponder platform, thereby achieving the management and supervision of aircraft and maintaining air traffic order. In response to the test requirements of a certain type of transponder, the OP7200 is used to build a transponder automatic test system.

2.1 OP7200 interface application

As the control and display unit of the transponder automatic test system, OP7200 is responsible for the scheduling of the entire system test tasks, data processing, interface control, result display and other tasks. Its interface is shown in Figure 4. The tasks it completes include the following: 1) Interface display, completed by LCD display screen; 2) Interface switching, working mode selection and control, parameter input, etc., completed by touch screen; 3) Test interface switching, completed by 9 buttons (whose functions can be replaced by touch screen); 4) Channel selection in the relay switch circuit, completed by 8 digital outputs; 5) Measuring the voltage output by the detector to determine whether the transceiver is working, completed by 1 A/D conversion; 6) Communication of the transceiver detection circuit and the communication of the RF module control circuit, respectively completed by two 3-wire RS232 interfaces; 7) Communication of the control box analog circuit, completed by RS485 interface; 8) Information exchange is completed by Ethernet interface. At the same time, OP7200 uses 27 V DC power supply.

2.2 OP7200 Software Design

When the system starts, first perform system initialization operations; set the backlight on to increase the brightness of the LCD display; set the contrast of the LCD to make the display interface clearer; initialize the keyboard; initialize the font size; create a touch screen keyboard; initialize the serial port, set the baud rate, data bit, check bit, stop bit, etc. of RS232 and RS485; set the output port and Ethernet. Then initialize the global variables and complete the definition of global variables; then enter the test task selection interface to determine whether to perform the test. If you choose the whole machine online test or the transceiver test, you will return to the initial interface after the test task is completed, otherwise it will keep looping in the initial interface program. The software flow is shown in Figure 5.

When designing the program, cooperative multitasking was adopted. When there is no need to execute an immediate task, each individual task will automatically comply with its running time. Through the interconnection statement const and public functions, variables can be shared between different tasks without strict precautions. Taking the transceiver test program as an example, operations such as transceiver interface display, received data processing, and touch screen control need to be implemented. By adopting cooperative multitasking, the test task can be completed well.

2.3 Matters needing attention during use

When using OP7200, you should pay attention to the following issues: the digital output port has two modes of drain output and source output, which should be selected according to the specific situation; the analog input channel has two modes of single-ended input and differential input, and each has multiple input ranges. When using it, you should choose the appropriate input range according to the specific situation; when using the keyboard or touch screen to call the data input function, the keyboard and touch screen each have their own functions. At this time, the keyboard and touch screen cannot be used at the same time. The keyboard function or touch screen function should be called according to the design requirements; software design should try to avoid using floating-point operations, otherwise it is easy to cause truncation and affect data accuracy.

2.4 Effect Analysis

OP7200 is small in size and light in weight, meeting the requirements of portable test systems; it has rich interfaces, and does not need to purchase additional boards and input/output devices like PCI04 or industrial computers, saving development time and cost; Dynamic C software development platform is an improvement based on standard C language, and is basically compatible with the programming rules of standard C language, and provides special library functions, such as touch screen digital input library functions, which can facilitate the input of integers, decimals, etc., not only making the design more user-friendly, but also facilitating programming and improving software development efficiency.

3 Conclusion

The transponder automatic test system based on OP7200 completed the test task well, with reliable performance and convenient operation through the touch screen, which effectively improved the maintenance and support capabilities of the transponder. Practice shows that OP7200 is a display control terminal with rich interfaces and relatively complete functions. It has a high cost-effectiveness in the design of portable test systems and has a good application prospect.