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Abstract— PCI eXtension for Instrumentation (PXI) is a rugged PC-based platform that offers a high-performance, low-cost deployment solution for measurement and automation systems. PXI combines the Peripheral Component Interconnect (PCI) electrical bus with the rugged, modular Euro card mechanical packaging of CompactPCI and adds specialized synchronization buses and key software features. PXI also adds mechanical, electrical, and software features that define complete systems for test and measurement, data acquisition Building on PXI capabilities, PXI Express provides the additional timing and synchronization features of a 100 MHz differential system clock, differential signaling, and differential star triggers. By using differential clocking and synchronization, PXI Express systems benefit from increased noise immunity for instrumentation clocks and the ability to transmit at higher-frequency rates. So the purpose of this paper is to use Ni PXIe to acquire real time system parameters and system interlocks using real time operation system for better deterministic approach.

[IndexTerms—Bandwidth, Data Acquisition, latency, PXIe, RTOS]

I. INTRODUCTION

he PXI industry standard has quickly gained adoption and grown in prevalence in test, measurement, and

control systems since its release in 1998. PXI is being selected as the platform of choice for thousands of applications, from areas such as military and aerospace, consumer electronics, and communications, to process control and industrial automation. One of the key elements driving the rapid adoption of PXI is its use of PCI in the communication backplane. Now, as the commercial PC industry drastically improves the available bus bandwidth by upgrading from PCI to PCI Express, PXI has the ability to meet even more application needs by integrating PCI Express into the PXI standard. To ensure the successful integration of PCI Express technology into PXI and CompactPCI backplanes, engineers within the PXI Systems Alliance (PXISA), which governs PXI, and the PCI Industrial Manufacturers Group (PICMG), which governs CompactPCI, have worked to ensure that PCI Express technology can be integrated into the backplane while still preserving compatibility with the large installed base of existing

systems. With PXI Express, users will benefit from significantly increased bandwidth, guaranteed backward compatibility, and additional timing and synchronization features. [1]

II. THE BASICS OF PXI EXPRESS[2] PXI Express integrates PCI Express into the PXI

backplane. We will first go over the advantages of PCI Express over PCI. PCI Express was introduced to improve upon the PCI bus platform. The most notable PCI Express advancement over PCI is its point-to-point bus topology.

Fig.1. PXI Express provides the highest bandwidth and lowest latency in the test and measurement industry.[2]

When considering the technical merits of alternative buses,

bandwidth and latency are two of the most important bus characteristics. Bandwidth measures the rate at which data is sent across the bus, typically in MBytes/s, while latency measures the inherent delay in data transmission across the bus. A bus with high bandwidth would be able to transmit more data in a given period than a bus with low bandwidth. A bus with low, meaning good, latency would introduce less of a delay between the time data was transmitted on one end and processed on the other end. PCI Express has excellent bandwidth and low latency compared to PCI.

The shared bus used for PCI is replaced with a shared switch, which provides each device its own direct access to the bus. Unlike PCI, which divides bandwidth between all

Sneh Soni Anuradha Tandon Keyur Mankadiya Student of Control &Automation Assistant Professor Project Leader Nirma Institute of Technology Instrumentation & Control Engineering Optimized Solutions Pvt. Ltd Project Trainee at Nirma Institute of Technology Ashram Road Optimized Solutions Pvt. Ltd. Ahmedabad Ahmedabad Ahmedabad Email: keyur@ospl.in Email: sneh100ni23@yahoo.com

High Speed Real Time Data Acquisition System using PXIe Technology.

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2013 Nirma University International Conference on Engineering (NUiCONE)

978-1-4799-0727-4/13/$31.00 ©2013 IEEE

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devices on the bus, PCI Express provides each device with its own dedicated data pipeline. Data is sent serially in packets through pairs of transmit and receive signals called lanes, which enable 250 MBytes/s bandwidth per direction, per lane. Multiple lanes can be grouped together into x1 (“by-one”), x2, x4, x8, x12, x16, and x32 lane widths to increase bandwidth to the slot. PCI Express dramatically improves data bandwidth compared to PCI buses, minimizing the need for onboard memory and enabling faster data streaming. For instance, with a x16 slot, users can achieve up to 4 GB/s of dedicated bandwidth as opposed to the 132 MB/s shared across all devices of the 32 bit, 33 MHz PCI.

The main advantages of PCI Express (PCIe) over PCI are the following: • Software compatibility • High throughput (up to > 4 GBytes/s) • Scalable bandwidth • Dedicated bandwidth per slot • Peer-to-peer communication • Long life (20+ years in mainstream market)

PCI Express. Systems built on PCI Express give you the greatest flexibility to attach to other I/O.

PXI Express specifies hybrid slots to deliver signals for both PCI and PCI Express. With PCI Express electrical lines connecting the system slot controller to the hybrid slots of the backplane, PXI Express provides a high bandwidth path from the controller to backplane slots. Using an inexpensive PCI Express-to-PCI bridge, PXI Express provides PCI signaling to all PXI and PXI Express slots to ensure compatibility with PXI modules on the backplane. With the ability to support up to a x16 PCI Express link in addition to a x8 link, the system controller slot provides a total of 6 GB/s bandwidth to the PXI Express backplane, representing more than a 45X improvement in PXI backplane throughput. By integrating PCIe into the PXI backplane, we can get up to 2 GBytes/sec/direction dedicated bandwidth per slot, up to 6 GBytes/sec/direction to the host, up to 18GBytes/sec/direction system bandwidth; enhanced synchronization capabilities (100 MHz differential clock and differential triggering); and backwards compatibility. The first PXI Express chassis will provide PXI peripheral slots. Additionally, by taking advantage of the available pins on the high-density PXI backplane, the PXI Express hybrid slots are capable of delivering signals for both PCI and PCI Express. In doing so, these PXI Express hybrid slots provide backward compatibility that is not available with desktop PC card-edge connectors, where a single slot cannot support both PCI and PCI Express signaling. Thus, the hybrid slot allows you to install a PXI module that uses PCI signaling or a future high-performance PXI Express module that uses PCI Express signaling.

By maintaining software compatibility between PCI and PCI Express technology, the specification drastically reduces cost for vendors and integrators to insert new PCI Express technology into existing test systems. With hardware compatibility provided by the hybrid slot and software compatibility, the cost of adding PXI Express technology is minimal.

The integration of PCI Express into PXI allows the platform to reach new applications.

Examples include the following: • High frequency, resolution IF / RF systems • High speed digital interfaces • High channel count data acquisition • High speed imaging

III. WHAT ARE THE DIFFERENT TYPES OF SLOTS IN A PXI EXPRESS CHASSIS?

A PXI Express chassis can include the following: A system slot, which accepts an embedded or remote PXI

Express controller PXI peripheral slots, which accept PXI modules

PXI Express hybrid peripheral slots, which accept PXI Express peripheral modules, 32-bit CompactPCI peripheral modules, and hybrid-compatible PXI peripheral modules

A system timing slot, which accepts both PXI Express peripheral modules and PXI Express system timing modules

Fig.2. The backplane layout for an NI PXIe-1062Q PXI Express chassis comprises multiple slots.[2]

A. Providing Additional Timing and Synchronization Features

PXI Express not only retains the timing and synchronization features of PXI, but also adds new capabilities by taking advantage of the technological advances that provide high-performance, low-cost differential signaling. Building upon the existing features of PXI, some of the additional timing and synchronization features provided by PXI Express include a differential system reference clock and differential star triggers, as shown in Figure 3.

By using differential signaling, PXI Express systems benefit from increased noise immunity for synchronization signals and the ability to transmit higher frequency clocks.

In addition to providing improved system accuracy and performance, high-frequency clocks interface well with modern processes and reduce module prices by removing the need for components such as clock multiplication circuits.

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Fig.3. By building on the existing capabilities of the PXI platform, PXI Express provides additional timing and synchronization features to achieve better measurement accuracy and handle new applications.

Basic PXI Modules [3] are listed below.

• Analog Input and Output • Digital Input and Output • Timing Input and Output • Power Supplies

IV. PXI CONTROLLER Most PXI chassis contain a system controller slot in the leftmost slot of the chassis (slot 1). You can choose from a few options when determining the best system controller for an application, including remote controllers from a desktop, workstation, server, or laptop computer and high-performance embedded controllers with either a Microsoft OS (Windows 7/Vista/XP) or a real-time OS (LabVIEW Real-Time). PXI Embedded Controllers - Embedded controllers eliminate the need for an external PC, therefore providing a complete system contained within the PXI chassis. These embedded controllers come with standard features such as an integrated CPU, hard drive, RAM, Ethernet, video, keyboard/mouse, serial, USB, and other peripherals, as well as Microsoft Windows and all device drivers already installed. They are available for systems based on PXI or PXI Express, and you have your choice of OSs, including Windows 7/Vista/XP or LabVIEW Real-Time.

V. REAL TIME DATA ACQUISITION AND CONTROL MODULE SOFTWARE DESIGN USING LABVIEW.

Practical Requirement The requirement is to acquire system parameters like Power supplies status, Voltage and Current Signals coming from different power supplies, cooling system status, Interlocking system and other incoming status signal. After acquisition it process acquired data and control whole system the proposed problem requires complete hardware system controlled by graphical user interface to achieve user define goals. Solution: PXIe chassis integrated with controller and I/O cards are system’s access point to field instruments. It continuously acquires & monitors the status and control signals of power supplies, process parameters and it controls field instruments.

The real time data acquisition hardware in turn communicates with host PC on Ethernet. Host PC carries host application designed in LabVIEW software which provides graphical user interface to user.

Fig.4. System Architecture

A. Host Application

The labview designed Graphical User Interface will be the

communication medium for user with the functioning system. Graphical User Interface representing system block, indications and result oriented pages. PXIe System will acquire data. PXIe System will be controlled by application running on Host Pc. User can control and monitor system parameters from GUI.GUI based part will run on windows environment.

According to the application we require Analog input, Digital Input modules to fetch different types of Analog signals like voltage, current and digital signals like on and off condition of Power supplies , Analog output, Digital Output PXI modules to generate required Voltage and current and to on and off desired power supply.

B. Selecting an Operating System

If you only want to acquire real-time data, you may not need an RTOS. There are many data acquisition (DAQ) devices that can acquire data in real time even though they are controlled by programs running in Windows. The DAQ device has an onboard hardware clock that ensures a constant rate of data acquisition.

However, consider an application where every data point must be acquired and analyzed by software before you can determine if an event has occurred that requires a response. Similarly, consider an application where every acquired point must be handled by software in order to determine the output of a control loop. In both these cases, the software and the operating system must behave deterministically. In this case you require an RTOS to guarantee response within a fixed amount of time. Key factors in a real-time OS are minimal interrupt latency and minimal thread switching latency. A real-time OS is valued more for how quickly or how predictably it can respond

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than for the amount of work it can perform in a given period of time [5].

Fig.5. Selecting an Operating System

As the requirement is a critical application requiring determinism, priority of tasks, scheduling of tasks an integrated part of the whole system, Acquisition must be done as microseconds part will be executed in PXIe real time for better deterministic approach and GUI based part will run on windows environment. Real Time module has several loops to perform its deterministic operations. Each loop will used to perform specific deterministic operation.

There will be some loops to execute some file I/O activity this loops are running in real time operating system so acquires data in microseconds. There will be one loop for acquire all analog input signals using PXIe Analog Input module. This loop will acquire all analog input channels at specific sampling rate. This data will send to host to monitor these signals. Logging rate for acquired channels would be at normal sampling rate for each channel in normal acquisition. At the time of interlock the data will be logged at the maximum achieved sampling rate.

There will be one separate loop for analog output signal. This loop will continuously send analog output value to PXIe Analog Output module. These signals are control signal coming from host which is entered by user according to system requirement.

As same way there will be a separate loop for digital output. This loop will continuously send digital output signal to PXIe Digital Output Module. This digital output will use to on and off different system devices which are also signal send by user

C. Requirement of FPGA Based Software

FPGA is used to respond the system interlock and critical signal in terms of micro seconds. Process Interlock are Something that prevents incorrect operation or possible damage to the process or equipment. As FPGA card is controlling using RT Controller hence FPGA target will be created under the RT Target. In FPGA VI there will be one loop. FPGA will continuously read all interlock inputs and

write it into the FIFO to read the same into the RT side if interlock is enabled by user. This loop will also execute the interlock logic of the system and generate corresponding Digital Output to respond the interlock. This loop will responsible to respond the system interlocks in nano seconds. Interlock sequence can also be calculated inside this loop of FPGA.[4]

VI.CONCLUSION

Thus PXIe which comes under PCI eXtensions for Instrumentation (PXI) is a rugged PC-based platform that offers a high-performance, low-cost deployment solution for measurement and automation systems. PXI Express provides the highest bandwidth and lowest latency in the test and measurement industry. We can use different PXIe modules according to the system requirement we can use Windows operating system for normal Applications or Real-time operating system for high determinism and accuracy [6]. Additionally FPGA module can be inserted in PXIe chassis to respond the system interlock and critical signal in terms of micro seconds. We can acquire data through PXIe Analog Input and Digital Input Modules and send controlling signals for system by Analog Output and Digital Output Modules.

VII.REFERENCES

[1] PXI EXPRESS SPECIFICATION TUTORIAL

http://www.pxisa.org/files/resources/Presentations%20&20Tutorials/PXI%20Express%20Specification%20Tutorial.pdf

[2]PXI Express FAQ , http://www.ni.com/white-paper/3882/en [3] Parts of a PXI System http://www.ni.com/white-paper/4811/en/ [4] PXI Express Hardware Specification Revision 1.0 ECN

http://www.pxisa.org/userfiles/files/Specifications/ PXIEXPRESSHWSPEC_ECN1R2.pdf [5] "RTOS Concepts" http://www.chibios.org/dokuwiki/ doku.php?id=chibios:articles:rtos_concepts [6]Real time plasma disruptions detection in JET implemented with

the ITMS platform using FPGA based IDAQ Published in Real Time Conference (RT), 2010 17th IEEE-NPSS Author(s)Ruiz, M. Instrum. & Appl. Acoust. Res. Group, Tech. Univ. of Madrid (UPM), Madrid, Spain Vega, J. ; Ratta, G. ; Barrera, E. ; Murari, A. ; Lopez, J.M. ; Arcas, G. ; Melendez, R.