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PC104-based Universal Automatic Test System

In Electronic Infomation Category: P | on April 19,2011

Universal Automatic Test System platform can maximize the test cost savings, including the cost of software development, system maintenance, upgrade costs and XC2V2000-4BG575C datasheet and the new measurement system development costs.

TPS test program set to develop a portable program can allow for many different occasions (ideal state), the system does not need to do too much duplication of development work, for different equipment manufacturers, TPS without changes ; Instrument Interchangeable make the system do not need to upgrade the software maintenance equipment replacement to make any changes, just a simple configuration can continue to use, reducing the cost of maintenance and XC2V2000-4BG575C price and upgrades; test system for new development, if the TPS and XC2V2000-4BG575C suppliers and the instrument, channel can use the existing resources, then will make the new test system development becomes easier, faster and lower cost.

Based on the PC104 computer, a common way of testing the system set up. The system consists of control, measurement and control bus, measurement and control modules, measurement and control instruments and other components, the bus, including GPIB, VXI, MXI, PXI, etc., monitoring and control module includes both desktop machines and equipment, including virtual instruments and synthetic instruments. In the general interface, data transmission, communication protocols, instrument module configuration, signal conditioning such as transfer standards to establish a unified understanding of a variety of instruments and equipment to make this platform After the formation of automatic test system, according to testing needs to play their own effectiveness Most of the tests meet the requirements.

1 system hardware design

1.1 Component selection

1.1.1 Host selection

PC104 computer technology is more mature at this stage, but also the future development trend of measurement and control technology. Relative to PC104 computer desktop IPC are smaller in size, low power consumption, high reliability and low environmental requirements of work, it is widely used in distributed systems and distributed control systems. PC104 highly compact structure, size, typically only: 100mmx90mmx15mm, can facilitate the design of highly integrated equipment, industrial machines than desktop connection with the complexity of the system to build up compact. The supply voltage only 5 V, power is only 10 W, while the general IPC IPC is required about the current 300 V, 250 W is also about power, can be seen using the PC104 computer can significantly reduce consumption. Operating frequency is now able to achieve 1 GHz, 64 KB level two cache and 2MB cache above, the data processing and analysis to achieve faster speed. In the interface area, with a LAN port, an EIDE interface, 2 serial ports, 2 USB interface, keyboard and mouse interfaces, CRT interface, in a very small space to achieve almost all the features of the PC unit, to achieve data efficient transmission and a variety of communications. PC104 current stage of development of computer technology is more mature, but also the future trend for the formation of the system, either as an external industrial machine, can also be used as an embedded computer. So use the PC104 computer as a host, its adaptability, flexibility, can meet the needs of modern testing, but also take into account future developments in the field test.

1.1.2 Instrument selection

IVI (Interchangeable Virtual Instruments), Interchangeable Virtual Instruments VXI plug and play in the (VXI plug & play) developed from the technology of todays most advanced test technology. In the device selection, try to choose the instruments meet the IVI class specifications, can achieve better interoperability, by compiling the PC104 computer IVI class driver to achieve a certain type of IVI instrument control. IVI instrument drivers interchangeability of major research, testing, performance, development flexibility and quality assurance testing. It combines the end-users, equipment manufacturers and through an open and transparent way to construct test instrument control system, the needs of system integration, state management of its unique structure, you can not re-optimize the design of hardware systems, starting from the test system software architecture, eliminate redundant tests and improve the testing speed. It compared VXI plug & play technology, the main advantages are: consistent VXIplug & play specification classes are installed with the computer equipment Although you can directly use a good driver, but each time the instrument changes need to load drivers, and test procedures have make certain changes, instrument interchangeability is not strong enough; and comply with IVI instrument class specification, the instrument changes, the computer loaded by a good IVI class driver, simply call in the program will be the drivers in this category control of the instrument can be realized.

1.2 hardware configuration

1.2.1 hardware

Computer hardware solutions for the test system based on PC/104. Mainly includes 3 parts: 1) to complete the PC/104 computer-based measurement, control, data processing and other functions of the parts; 2) to achieve PC/104 computer to communicate with the outside world transfer interface section; 3) Chassis parts. The system structure shown in Figure 1.

Figure 1 System structure diagram

The schematic composition of each module of each subsystem or not to build or to join, according to the group need to be flexible with the actual test, cutting, building automated test systems. Set out below several major programs:

Formation Scenario 1: When less data on the test speed under less demanding circumstances, the host part of the configuration in the PC/104 GPIB card, GPIB bus with a VXI or PXI chassis of equipment to control, by the PC/104 host to complete testing tasks.

Formation of Scenario 2: When the data are more demanding on the test speed under the circumstances, you can choose high rate of MXI bus, by setting the host part of the PC/104-MXI in turn PC/104 interface, complete PC / MXI bus 104 bus and the communication, the implementation of the VXI or PXI instrument chassis to exercise control, to complete the test.

Formation of Option 3: In the PC/104 host part of the added A / D sampling module, the multiplexer module, timer module, the measured object via USB or RS232 data cable and the PC/104 host part of a direct communication with desktop machines, so in order to build a small PC/104 based test system to complete the test.

Formation of Option 4: the host part of the design in a variety of PC/104 bus switch interface, switch interface in accordance with a variety of design, not only to build VXI and PXI test system, you can also set up other bus test systems, only configuration the appropriate interface to the bus transfer.

Formation program 5: Bus control is the future trend, coupled with the host part in the PC/104 bus interface, direct access to the PC/104 bus and direct connection to the host, the implementation of communication, can be external, or directly embedded systems to achieve system testing, save development costs, but also to adapt to the future development needs, reflecting the openness of the system.

Formation program 6: LAN port through the PC/104 connector on the server, the access network interface cards can also be designed so that multiple PC/104 host via optical fiber communications, test and implement a distributed network, to remote collection , control.

1.2.2 basic principle

PC/104 computer through GPIB or MXI bus to the VXI / PXI chassis to control, to complete the test tasks. PC/104 computer to compile the IVI class driver on the implementation of a class of IVI instrument control. Depending on the signals and incentives, can choose different IVI instrument classes, such as oscilloscopes, DMM, arbitrary waveform / function generator, power meter, etc., the measured object to return the excitation signal is higher, the signal through the adapter box to complete the conditioning, conversion and pretreatment into the VXI / PXI chassis, coupled with the programmable power supply, signal generators, spectrum analyzers and other instruments, including the desktop, or add PXI devices, complete the entire testing process.

Able to adapt to the basic needs of a variety of tests, from the above scenario can be drawn in this basic set up an automated test system, can be added to the bus, the bus or not to build a small test system configuration, based on this basic set up test system in Figure 2.

Figure 2 test system set up

1.3 transfer interface design

PC/104 host to achieve the communication with the outside world, transfer interface design is one of the very important aspects. In this scenario, the PC/104 bus, MXI bus transfer interface design is good or bad is a matter of the whole system can achieve high-speed testing of the key. Complex programmable logic device (CPLD) for almost all of the arrays and digital integrated circuits of all sizes, with its easy programming, high integration, fast, low prices more and more popular designers. Switch interface is designed to complete the requirements by CPLD. Interface design shown in Figure 3.

Figure 3 Schematic diagram of the system

Selected through PC/104 bus and bus timing, signal, address, data, needs analysis, design interfaces with the CPLD module, the bus handshake and data transfer capabilities. C-PLD part of the circuit shown in Figure 4.

Figure 4 C-PLD part of the circuit

PC/104 bus resources are mainly used in I / O and interrupt control, the specific signal as follows: A [019] is a PC/104 10-bit address bus; D [07] is a PC/104 8-bit bi-directional data bus; IOR, IOW are bus I / O port read and write signals; AEN is to allow DMA control of the address bus, data bus and DMA transfers to read and write command lines as well as memory and I / O devices read and write; IOCHRDY is I / O Ready signal, I / O Channel Ready is high; SYSCLK is the system clock signal, allowing the system to synchronize with external devices; IRQ3 is the interrupt signal. PC104 part of circuit shown in Figure 5.

part of Figure 5 PC104 circuit

1) data transfer (PC/104 MXI) PC/104 needs to transmit data, PC/104 set AEN signal, by sending address and data bus to send data to the CPLD, IOW pin low at this time (effective). When the CPLD receives the correct data, driven MXIbus address strobe AS, for address information, and then drive the data strobe MXI DS, set the data read and write signal WR removed by MXI to determine the response signal DTACK whether the data transfer is completed, then send the next data is completed, MXIbus is used in the form of multiplexed address data bus.

2) data transfer (MXI PC/104) when MXI transmit data to the CPLD, the set AS, driving the data strobe DS, and WR valid to send data. CPLD received data, sent through the IRQ3 interrupt request to the PC/104, PC/104 interrupt signal is received, the first set AEN, then IOR become low, the address read from the CPLD register data port.

2 system software design

2.1 software development environment

The choice of the program to meet the instrument specifications IVI instrument-based, so the software choice should be to facilitate the IVI instrument driver development as a fundamental category. IVI instrument driver development class has more of software, such as Labview, Labwindows / CVI and so on. By Labwindows / CVI for test control technology developed is based on the standard C language programming tools, and its in the panel, interface, code generation are rather convenient, dynamic link library contains the *. dll, with IVI control library, which contains the IVI instrument driver development wizard, you can save a lot of instrument driver development time. Therefore, software development tools should choose Labwindows / CVI.

2.2 software is the basic structure

Software program should include three parts: the test program, interface program, IVI class driver. The main test program to complete the basic requirements and test equipment self-test, and its main functions include: system management, resource allocation, self-calibration, interface, query, data processing and so on. Interface program features should be: data storage, signal transfer, instrument control, channel selection, the results determined and so on. IVI class driver according to their specifications are: instrument drivers, special driver, compatible driver, custom driver and IVl class driver. The functional structure shown in Figure 6.

software function block diagram in Figure 6

Software testing process, including the IVI configuration, system configuration, data collection, data storage, such as the IVI class in the system do not need equipment, just set up a small test system, the software design, also do not configure the IVI class driver When the end of a test task, such as there are data to test, then continue to collect data for testing, or the end of the test, the software testing flow chart shown in Figure 7.

Figure 7 flowchart software testing

IVI classes do not meet the standard instrument, can not meet the IVI standard instrument as the same logical name in the definition of the following test procedure can guarantee the relative hardware independence. Taking into account a certain number of years in the use of test system, the replacement of such devices may, in particular the switch to a different company may be the same type of equipment. In order to reduce the amount of changes to testing procedures, the procedures for such devices and the need to complete the initialization of the task procedures to function in the form of instrument packages at different dynamic-link library files in the *. dll. In the specific test procedures, when required to operate an instrument to accomplish a task, according to the corresponding need to call the relevant dynamic link library function. When the need to replace such equipment, if the original. dll file to complete the required function does not work, you can for the replacement of the equipment, maintain the original function name and parameters remain unchanged, re-write the relevant procedures, generate a new same name. dll files. This extensive testing procedure can not be recompiled, simplifying the upgrade. Application of


Airborne equipment test equipment in the design of an adopted design of the program ideas and concepts. For the overall performance of the test system * assessment, integrated hardware and software in the system after the signal test on-board equipment to experiment with digital signal which is the basic system test bed, including PC/104 computer, PC/104-MXI interface adapter , VXI chassis, IVI class of instruments, general instruments. The results shown in Table 1.

Table 1 and the accuracy of test results

Can see that the system is stable and reliable, and transferred through the interface PC/104-MXI, PC/104 bus, MXI bus, and data transfer speeds of up to 10 MB / s, increase the test efficiency of the test to solve the GPIB low speed on the bottleneck.

4 Conclusion

The solution is based on PC104 computer, for most of the testing requirements and the different situations to consider proposed group with the flexibility, tailoring and design of the Universal Test System platform. The entire system is modular, standardized, serialized designed to meet the future development of automatic test system trends, reflecting the universal principles and take full account of the composition development. Of course, the actual building test system is a difficult and complex process, the proposed establishment of several programs, for reference, is intended to provide ideas, users can test their actual needs and requirements of this platform, a flexible test system set up to complete the testing tasks.

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