DSPA64 USER MANUAL EXCERPTS

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The table of contents and selected excerpts from the DSPA64/HLF manual are shown below. The full text is available in PDF format at no charge from our downloads page.

CHAPTER 1: INTRODUCTION
The Symmetric Research DSPA64 A/D data acquisition board provides an easy way to acquire and process data on your PC from up to 64 channels at sampling rates from dc to acoustic frequencies. It has been designed to work in conjunction with the SR DSPHLF coprocessor board, providing the up front processing power of a DSP32C along with a full 1 MB of buffering capability. The large buffering along with the transparent DSP32C host PC interface allows for continuous real time data acquisition to the hard disk with no dead time.

Based on the Burr Brown DSP101 A/D converter, the SR DSPA64 has a single converter and a 64 channel analog multiplexer. The multiplexer is under program control of the DSPHLF card, and can be set to scan the input channels in any order, making a new channel selection between each sample. This provides considerable flexibility for scanning inputs from a variety of sources, where the full sampling rate of the DSP101 can be spread across the 64 input channels in any manner. For example, when the DSP101 is sampling at the factory default of 138 kHz and sampling is spread evenly across all 64 channels, an effective rate of 138/64 = 2.156 kHz on each channel results.

Software included with the board is aimed at providing support so data can be immediately acquired and the user can become familiar with the board's technical operation. Source code for all software is included so those interested in customizing the system for their own applications have the information they need.

Other items included with the board include a 110 vac power supply, a ribbon cable for connecting to a DSPHLF board, and complete circuit diagrams.

CHAPTER 2: INSTALLATION
Installation of the DSPA64 is straightforward. Basically, the DSPHLF board is plugged into the PC ISA bus, while the DSPA64 board sits outside the PC and is connected to the DSPHLF via a ribbon cable. A power supply and your differential analog signal inputs must also be hooked up to the DSPA64. The basic configuration is indicated in Figure 1, where the exact steps are:

CHAPTER 3: HARDWARE BASICS
The circuit of the DSPA64 is straightforward. The analog portion of the board has a 64 channel analog multiplexer array, followed by an instrumentation amplifier and A/D converter. The digital portion of the board takes care of controlling the A/D conversion rate, receiving the next multiplexer channel from the DSPHLF DSP32C coprocessor board, and sending the newly converted A/D values back to the DSPHLF.

The DSPHLF board is installed inside the PC and communicates with the DSPA64 via its high speed DSP32C serial port. This is not an RS232 port. It is a 16 Mbit per second interface designed primarily for communicating with devices like A/D converters.

CHAPTER 4: DLL LIBRARY SUPPORT
Win 95 32 bit DLL library support is at the core of the software supplied with the SR DSPA64/DSPHLF system. With these functions, system operation can be controlled from high level languages without having to know the low level details. These functions can be called from Microsoft Visual C and Basic, and National Instruments LabView. This chapter covers usage from programming environments like Visual C. For information about usage from LabView, see the LabView chapter. For low level programming information see the Low Level Examples chapter.

The general outline of how to use the dspa64.dll functions is fairly simple. There is an Init function to set the channels to be scanned and other parameters. Once the board has been initialized, then the Start function should be called to begin execution. While executing, IsReady can be called to determine when the DSPA64 has acquired data, and can be followed by calling GetData to copy the data from the DSPHLF board into PC memory. The data can then be displayed or saved to the hard disk by the user. Note that transfer of data from the DSPHLF to the PC's memory is transparent to all data acquisition. Acquisition continues on without interruption.

CHAPTER 5: FINISHED APPLICATIONS
The SR DSPA64/DSPHLF comes with two finished Win 95 application programs you can run immediately after installing the hardware and software. These programs will help you become more familiar with the system, and may fill your entire acquisition needs. The source code is included for those wanting to modify the programs for custom applications.

Simpa64.exe is a simple text only command line program, while scopea64.exe is a full Win 95 graphical user interface GUI display program. Both save their output data to binary files in the same format for further processing. They have been written in C and C++ respectively, and their source code can be found in simpa64.c and scope.cpp.

CHAPTER 6: LABVIEW SUPPORT
Support for National Instruments LabView is provided in the LabView LLB VI library \sr\dspa64\labview\dspa64.llb. This LLB contains 1 application and 18 utility VIs. The scope application VI is a complete data acquisition program that relies on the underlying utility VIs. The utility VIs are in turn wrappers around the corresponding core dspa64.dll DLL functions which supply the low level support for all SR DSPA64 software.

The DSPA64 application VI is described below. For additional information, please refer to the descriptions of the underlying DLL functions or use the Window>Show VI Info... menu option to access the information stored within each VI itself. The application and utility VIs have been saved unlocked and with their block diagrams included so you can modify them as needed to fit your application.

CHAPTER 7: LOW LEVEL EXAMPLE PROGRAMS
Low level example programs are included with the DSPA64/DSPHLF for users wishing to understand the fundamental programming details of the system. These examples progress from simple to more complex with config.dsp approaching the core DSP driver used with the finished applications simpa64.exe and scopea64.exe

A brief overview of each program is covered in this chapter. For more details the user should refer to the comments in the respective source code files: sample.dsp, sample18.dsp, filter.dsp, switch.dsp, iconfig.dsp, and config.dsp.

CHAPTER 8: SYSTEM DIAGNOSTIC UTILITY
The SR DSPA64/DSPHLF data acquisition system comes with a diagnostic program to help you verify proper operation. If you suspect anything is wrong or just want to verify the system is installed and running, use this program. In addition, running any of the application programs like scopea64.exe is a good indication of proper installation. If any of those programs run you can be fairly confident that the system is functioning correctly without even having to run the diagnostic.

The diag.exe diagnostic program will check to make sure the DSPHLF board has been installed and is functioning. Then it will proceed on to test the DSPA64, reporting the results. Diag.exe runs in text mode only, so no graphics will be required. If a test fails, hints will be printed to the screen to suggest things to try.

APPENDIX A: ELECTRICAL SPECS & CALIBRATION
Note: for additional specs such as A/D resolution, please check the data sheet for the A/D chips.

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