Research on the architecture and implementation scheme of multi-bus fusion test system

With the transformation of informatization, high and new technologies have been widely used throughout the life cycle of weapons and equipment, resulting in a rapid increase in the complexity of weapons and equipment. The traditional test system structure based on a single bus has become difficult to meet the maintenance and support needs of weapons and equipment, mainly in the following aspects.

1) The single communication interface of the test system cannot meet the communication needs of weapons and equipment with multiple digital interfaces. In order to make weapons and equipment have high-performance combat capabilities, people often apply the latest research results of modern computer technology, electronic technology, and communication technology to them. The interfaces between weapons and equipment and the outside world usually include 1553B, RS422, and RS232. The interface forms are Diversified, the test system needs to be equipped with a variety of communication bus interfaces to meet the testing needs of weapons and equipment.

2) The functional coverage of single-bus measuring instruments is limited. Since there are many test items for weapons and equipment, complex test parameters, and a wide range of test resource requirements, the frequency coverage of the measurement device needs to range from low frequency, radio frequency to microwave. However, the current mainstream military test instrument bus (such as VXI bus) is limited to structural and instrument module factors, and has limited support for radio frequency and microwave measurement instruments. In this field, GPIB bus instruments show excellent performance.

3) The test system structure is limited. Due to the limitations of the measurement module's data acquisition capabilities and the test environment, the test system usually needs to trigger instrument modules on different buses and start a certain test at the same time to complete the measurement task. The test system often does not have a unified trigger structure that meets the above requirements.

4) The test system has poor portability and difficulty in updating and upgrading. Currently, there is a lack of interoperability between test systems of different services and different maintenance levels. This situation seriously affects the allocation of test resources, the generation of test sequences and the invocation of test results. The main factor affecting the interoperability of test equipment is that the buses of test equipment are diverse and incompatible with each other.

When it is difficult to build a test system using a single bus to meet the needs of weapons and equipment testing, integrating the advantages of multiple instrument buses and building a multi-bus integrated automatic test system based on multiple digital interface buses has become one of the development trends in the field of military testing.

1 Definition

Multi-bus integrated automatic test system: The test system contains two or more digital interface buses, and different buses can achieve mechanical compatibility, electrical compatibility, functional compatibility and operational compatibility. Interface transfer devices are used between different buses to achieve mechanical and electrical compatibility; communication between different types of instruments on different buses can shield the differences in I/O interfaces and achieve "bus I/O transparency"; similar instruments on different buses can communicate Shield functional differences, achieve "resource function transparency", and ultimately achieve operational and functional compatibility to meet the test system's interoperability and interchange requirements for different bus measuring instruments.

2 Overall framework of the test system

2.1 Multi-bus integrated test system architecture

The test system based on LXI can better meet the needs of automatic test system construction for multi-bus integration. The system structure block diagram is shown in Figure 1. LXI (LANeXtension for Instrument) is an extension of LAN local area network technology in the instrument field. LXI instruments are strictly based on IEEE802.3, TCP/IP, network bus, web browser, IVI-COM driver, clock synchronization protocol (IEEE1588) and standards New instrument in module size. The LXI module implements information browsing and program control with the help of a standard web browser, and communicates in IVI-COM format to facilitate system integration and interchange of instruments of the same type.

Figure 1 The overall structure of the automatic test system based on LXI multi-bus integration

In Figure 1, the system uses LXI to connect various instrument bus modules, and bus modules such as VXI, PXI, and GPIB become components of the system through interface adapters. The computer controller serves as the instruction executor of the entire test system under the control of the operating system. The operating system provides file management, memory management, user interface message response, test result output and printing, system I/O request processing and other services for the multi-bus integrated automatic test system.

At the system I/O layer, multi-bus mechanical and electrical compatible adapters are cross-linked with the system I/O interface to provide a variety of test bus interfaces. The system I/O interface also controls the "synchronous trigger control logic" to achieve synchronous triggering of different bus test resources. With the cooperation of software resources, it can meet the system's needs for simultaneous measurement of multiple signals.

The operational compatibility and functional compatibility layer of multi-bus integration mainly includes: system I/O bus driver layer, multi-bus test resource exchange driver layer, signal virtual resource requirements to physical resource configuration mapping layer, and signal-oriented virtual instrument layer .

The system I/O interface is connected to various instrument backplane buses (VXI, PXI, GPIB, etc.) through the instrument connection bus LXI, and measuring instruments are installed on the instrument backplane bus. The test interface adapter is connected to the measuring instrument. The test interface adapter completes the signal cross-linking between the measuring instrument and the unit under test, performs impedance matching transformation on the input and output signals, and completes tasks such as signal attenuation and level conversion.

The multi-bus fusion test system application software runs on the multi-bus test resource fusion layer. This layer does not contain specific physical resource information, and the program code is written in a signal-oriented and test requirement-oriented mode. The mapping of virtual test resources to specific physical devices is implemented in the multi-bus test resource fusion layer.

In order to ensure that the multi-bus integrated weapon equipment test system has a good human-machine environment, the system is equipped with human-machine interfaces such as monitors, keyboards, and mice, and output devices such as printers.

2.2 Multi-bus mechanical and electrical compatibility implementation plan

To integrate different test bus modules into an LXI test system, two technical solutions are available: development bridge adapters and interface adapters.

The bridge adapter consists of an LXI interface and a specific bus interface. The LXI interface implements all requirements of the LXI interface, including: network protocol support, Web page browsing and instrument control, LAN configuration initialization and IVI driver. On the specific bus interface side of the bridge adapter, specific hardware and software interface requirements are implemented. For example, if an LXI bridge adapter connects to a GPIB instrument, the bridge adapter must not only support the LXI interface and the GPIB interface, but also must have the ability to map software commands from the LXI side to the GPIB side.

The interface adapter completely converts the non-LXI bus interface into an LXI interface. Different from the bridge adapter, through the interface adapter, the host can directly access and control non-LXI instruments using instrument drivers and Web pages. There is no need for mapping of control and communication mechanisms and VISA resource mapping between the interface adapter and non-LXI instruments.

In the multi-bus convergence test system, in order to avoid significant changes in the original VXI, PXI, and GPIB system structures, the multi-bus convergence test system based on LXI uses a bridge adapter mechanism to seamlessly integrate existing bus instruments. into it. For example, for the VXI bus module, the EX2500 LXI-VXI Slot 0 InteRFace can be used to convert LXI instrument operation commands based on the TCP/IP protocol into signal drive logic on the VXI instrument backplane. Through this structure, the original VXI test system, as a subsystem of the system, only needs to make a few changes in the Agilent IO Library interface configuration, while the system hardware and test software can continue to be used without any changes.

2.3 Synchronous triggering structure of the system

Synchronization and triggering between different bus instruments are key aspects that must be considered in multi-bus integrated automatic test systems. Since the synchronization and triggering mechanisms of different test buses are quite different, it is difficult to achieve synchronization and triggering of an automatic test system with multi-bus integration.

In order to meet the system's high-precision trigger error requirements, the system uses a trigger structure that combines LXI's precision clock trigger IEEE1588 and LXI hardware trigger. The system trigger structure is shown in Figure 2. IEEE1588 provides a high-precision synchronous clock for the system, and LXI triggering provides unified event triggering with minimal phase difference for each bus module. The system's trigger HUB uses EX2100.

Figure 2 Trigger structure of automatic test system with multi-bus integration