CapturePlus II High-speed Data Acquisition System Features General Description High-speed Data Acquisition & Analysis Tool The CapturePlus™ II data acquisition system is a development tool that interfaces a Cirrus Logic evaluation board to a PCcompatible computer. Digital data is collected in a high-speed digital FIFO, then transferred to the PC over a USB connection. Evaluation software is included to analyze the data and demonstrate the ADC’s performance.
CapturePlus II TABLE OF CONTENTS 1. CAPTUREPLUS II HARDWARE OVERVIEW .......................................................................... 3 1.1 Kit Contents ....................................................................................................................... 3 1.2 Required Items Not Supplied ............................................................................................. 3 1.3 Minimum PC System Requirements ................................................................
CapturePlus II 1. CAPTUREPLUS II HARDWARE OVERVIEW CapturePlus II Hardware Board A (ARM9) Board B (Interface) DSP Operating System ROM Indicator LEDs USB Driver Cirrus Logic Evaluation Board Electrical Isolation DSP FPGA Ethernet Driver Electrical Isolation Electrical Isolation Data Acquisition Memory (RAM) 1.1 Kit Contents The following items are included in the CapturePlus II kit.
CapturePlus II 2. SOFTWARE SETUP The following section assumes the software is being installed from the CD-ROM included in the kit. The complete software install package and any software updates can be downloaded from www.cirrus.com/Industrialsoftware. 1. Insert the CapturePlus II CDROM into the PC. 2. If the CapturePlus II installer program does not start automatically, navigate to the CDROM root directory and run the SETUP.EXE program. 3.
CapturePlus II 3. HARDWARE SETUP The following section describes the connections between the Cirrus Logic evaluation board and the CapturePlus II system. It then describes the connections between the CapturePlus II system and the PC.
CapturePlus II 4. SOFTWARE DESCRIPTION The CapturePlus II Software user interface is divided into two sections: – The data control sub-panels are located on the left-hand side and bottom of the GUI display and are always available. – The tabs at the top of the GUI panels are always present and provide convenient access to configuration and data collection panels. – Click on a tab to display the desired panel. 4.
CapturePlus II 4.1.1 Device Sub-panel The Device sub-panel configures the CapturePlus II system to capture data from the evaluation board. This sub-panel is always available. Sub-panel Descriptions: – Pull-down menu: The pull-down menu selects the Cirrus Logic evaluation board and associated device. In most cases, the software will read the evaluation board EEPROM and automatically select the appropriate menu item. – Load Config: Loads the ADC internal register configuration file.
CapturePlus II – Timed Conversion or Continuous Conversion: Click on the toggle switch to change between Timed Conversion and Continuous Conversion modes. In Timed Conversion mode the CapturePlus II system forces the Desired Sample Rate to be met by applying the correct timing delay to the ADC trigger. Enabling Timed Conversion mode activates the Desired Conversion Rate window. Timed conversion sample rates are calculated based on the frequency displayed in the Clock Frequency window.
CapturePlus II 4.1.3 View Sub-panel Use the View sub-panel to select the evaluation board analog input channel data set on which the software performs calculations and plots data graphs. This sub-panel is always available, however there may be only one channel’s data set available for viewing. 4.1.4 Data Sub-panel Use the Data sub-panel to save, load, or clear the present ADC data set. This sub-panel is always available.
CapturePlus II 4.2 Menu Tabs The menu tabs are always present at the top of the software panels and provide access to configuration and data collection panels. The menu tab selects the currently displayed panel. Sub-panel Descriptions: – Communication Configuration: Displays the Communication Configuration panel. – General Configuration: Displays the scaling configuration for all software-generated graphs and calculations. – ADC Configuration: Displays the ADC Configuration panel.
CapturePlus II 4.2.1 Communication Configuration Tab The Communication Configuration panel establishes the communications link between the CapturePlus II system and the PC running the software. Select the Communication Configuration tab to display this panel. Click on any other tab to exit this panel. The Communication Configuration panel consists of the following sub-panels: – Selected Device Address: Displays communication address selected.
CapturePlus II USB Communications A USB communication link must be established between the PC and the CapturePlus II hardware before the CapturePlus II system can operate. To open communication to a USB connection perform the following steps: – Select an available USB device address by double clicking on a USB address within the Detected Devices sub-panel.
CapturePlus II 4.2.2 General Configuration Tab The General Configuration tab provides access to configure the scaling for all software-generated data graphs and calculations. Click on any other tab to exit this panel. The General Configuration panel contains the following sub-panels: Scaling: Use this button to select the magnitude units used for all software-generated data graphs and calculations.
CapturePlus II 4.2.3 ADC Configuration Tab The ADC Configuration tab provides a method for reading and writing to the ADC digital gain and offset registers. Select the ADC Configuration tab to display this panel. Click on any other tab to exit this panel. NOTE: This tab is not be available for all Cirrus Logic evaluation boards/ADCs. The ADC Configuration panel consists of the following sub-panels: – Gain Register: Displays the ADC GAIN Register contents in hexadecimal.
CapturePlus II 4.2.4 Configuration Tab The Configuration tab provides access to configure the ADC and the data acquisition system. Click on any other tab to exit this panel. The Configuration panel contains the following sub-panels: – Sample Settings: Provides a switch for manually setting the ADC SPI communications port in master mode or slave mode.
CapturePlus II 4.2.5 Time Domain Tab The Time Domain tab displays the data set in the time domain. Select the Time Domain tab to display this panel. Click on any other tab to exit this panel. The Time Domain tab consists of the following controls: – Data Graph: The Data Graph provides an x-y plot of the data set in the time domain. X-axis: Plots the sample number: Use the x-axis scaling to determine the position of any sample within the data set sequence.
CapturePlus II 4.2.6 Frequency Domain Tab The Frequency Domain tab displays the data set in the frequency domain. Select the Frequency Domain tab to display this panel. Click on any other tab to exit this panel. The Frequency Domain tab consists of the following controls: – Data Graph: The Data Graph provides an x-y plot of the data set in the frequency domain. X-axis: Plots Frequency in Hertz. The x-axis index is in units of Hertz for the FFT frequency bins.
CapturePlus II attenuation of 125 dB. Crystal 7 Term: The Hodie 5 Term Windowing Function is a proprietary 7-term digital filter optimized for examining an FFT with spectral content. It has a processing loss of 4.203dB and side lobe attenuation of 175dB. – Grounded Input FFT: Click on this button to change the voltage reference value used to calculate the dynamic performance values.
CapturePlus II 4.2.7 Histogram Tab The Histogram tab displays the data set using statistical analysis. Select the Histogram tab to display this panel. Click on any other tab to exit this panel. The Histogram tab consists of the following controls: – Analyze: After acquiring one or more data sets the Software will pause and wait for the Analyze button to be activated. Click on the Analyze button to analyze the data set and display the results. Only the last data set acquired is analyzed.
CapturePlus II – Variance: The variance statistical measurement is in units of volts2 or LSBs2 (least significant bits). The variance statistical measurement units are set by the Magnitude Display button in the General Configuration menu. – Minimum: The minimum statistical measurement is in units of volts or LSBs (least significant bits). The minimum statistical measurement units are set by the Magnitude Display button in the General Configuration menu.
CapturePlus II 5. CONFIGURING THE CapturePlus II SYSTEM The following sections describe how to configure the CapturePlus II system. The CapturePlus II system is designed to interface with a wide variety of Cirrus Logic evaluation boards. For this example set-up, the instructions show the CapturePlus II system being interfaced to a Cirrus Logic evaluation board. 5.
CapturePlus II Click the Connect USB button to connect the communications port. When a communications port is configured and communicating, the Connect USB button will no longer be highlighted and the Connected indicator will change to a bright green color.
CapturePlus II 5.2 Selecting the Cirrus Logic Evaluation Board Type In most cases the CapturePlus II system will automatically identify the evaluation board connected to the system. The software displays the selected evaluation board in the Device window. If the software Device window does not identify the correct evaluation board then use the Device pull-down menu to select the correct evaluation board.
CapturePlus II APPENDIX A. TESTING THE CIRRUS LOGIC CDB556x/7x/8x EVALUATION BOARD The following sections describe several basic tests performed to establish basic system functionality and baseline noise and distortion levels. A.1 A.1.1 Baseline Testing for Noise & Distortion Baseline Noise & Distortion Test - Non-Averaged FFT Connect the evaluation board power inputs to a bench supply having the appropriate voltages.
CapturePlus II Activate the Acquire button. Within the Acquire sub-panel set Select Number of Samples to Capture to 524288. Start the test run by clicking OK. Run time for this test is less than 1 minute for a 100 kSps ADC. When the data has been captured and is ready to be displayed, the Status window at the bottom of the screen will display Time Domain Analysis Complete. Click on the Analyze FFT button to display the FFT data.
CapturePlus II A typical FFT plot resulting from running a baseline test is shown below. Key information calculated from the captured data and displayed is the SFDR, SINAD, S/D, and SNR. A.1.2 Baseline Noise & Distortion Test - Averaged FFT Connect the evaluation board’s analog input(s) to circuit ground. Select the Frequency Domain window (selected by clicking on the Frequency Domain tab at the top of the screen). Activate the Grounded Input FFT and Log Freq Scale buttons.
CapturePlus II Activate the Acquire button. Within the Acquire sub-panel set Select Number of Samples to Capture to 524288. Click on Enable Averaged FFT. In this example, Averages have been set to 4. Start the test run by clicking OK. Run time for this test is approximately 1 minute for a 100 kSps ADC. A typical FFT plot resulting from running a baseline test is shown below. Key information calculated from the captured data and displayed is the SFDR, SINAD, S/D, and SNR.
CapturePlus II A.1.3 Baseline Noise & Distortion Test - Time Domain Analysis Connect the evaluation board’s analog input(s) to circuit ground. Select the Time Domain window by clicking on the Time Domain tab at the top of the screen. Click on the Acquire button. Within the Acquire sub-panel set Select Number of Samples to Capture to the desired sample size. This example uses a sample size of 256 to display data with a high level of detail.
CapturePlus II Start the test run by clicking OK. Upon completing the data capture, the screen will automatically display the results. A typical time domain plot resulting from running a baseline test is shown below. Key information calculated from the captured data and displayed is maximum, minimum, count (sample count), and magnitude.
CapturePlus II A.1.4 Baseline Noise & Distortion Test - Histogram Analysis Connect the evaluation board’s analog input(s) to circuit ground. Select the Histogram window by clicking on the Histogram tab at the top of the screen. Click on the Acquire button. Within the Acquire sub-panel, set Select Number of Samples to Capture to 524288. Set the Channel(s) to Capture to the desired channel(s).
CapturePlus II Start the test run by clicking OK. When the data has been captured and is ready to be displayed, the Status window at the bottom of the screen will display “Time Domain Analysis Complete”. Click on the Analyze button to display the histogram data. A typical histogram plot resulting from running a baseline test is shown below. Key information calculated from the captured data and displayed is mean, standard deviation, variance, minimum, and maximum.
CapturePlus II A.2 A.2.1 Measuring Analog Input Signals Setting Up the Input Signal Amplitude Connect the signal source to the evaluation board analog input(s). Select the Time Domain window by clicking on the Time Domain tab at the top of the screen. Click on the Acquire button. Within the Acquire sub-panel set Select Number of Samples to Capture to a small sample size; this example uses 256 to speed up the data capture process. Set the Channel(s) to Capture to the desired channel(s).
CapturePlus II Start the test run by clicking OK. At the end of the test run the screen will automatically display the results. A typical time domain plot from capturing a -0.5 dB input signal with a 24-bit ADC is shown below. Setting the desired signal level may require several iterations of adjusting the analog input signal level and then capturing and viewing the data.
CapturePlus II A.2.2 Measuring a Single Analog Input Signal A test to determine the evaluation board performance with a full-scale input signal can be performed once the hardware and software are configured. The following describes testing of the system using a typical full-scale input signal. Connect a 1 kHz, -0.5 dB signal into the evaluation board’s analog input channel. Select the Frequency Domain window by clicking on the Frequency Domain tab at the top of the screen.
CapturePlus II Click on the Acquire button. Within the Acquire sub-panel, set Select Number of Samples to Capture to 524288. Click on Enable Averaged FFT. In this example, Averages have been set to 4. Start the test run by clicking OK. Run time for this test is approximately 1 minute for a 100 kSps ADC. A typical FFT plot resulting from running a full-scale input test is shown below. Key information calculated from the captured data and displayed is the SFDR, SINAD, S/D, and SNR.
CapturePlus II A.2.3 Measuring Multiplexed Analog Input Signals The following section demonstrates how testing the evaluation board performance with full-scale, multiplexed input signals is performed once the hardware and software are configured. Connect a 1 kHz, -0.5 dB signal to one analog input channel, and a 5 kHz, -0.5 dB signal to the other analog input channel. Select the Frequency Domain window by clicking on the Frequency Domain tab at the top of the screen.
CapturePlus II Click the Acquire button. Within the Acquire sub-panel, set Select Number of Samples to Capture to 524288. Click on Enable Averaged FFT. In this example, and Channels to Sample have been set to All. Start the test run by clicking OK. To run this particular test setup takes approximately 1 minute for a 100 kSps ADC. The following pair of FFT plots show the results of running a typical 2-channel, multiplexed, full-scale input test. Activate the desired view by selecting Channel 1 or Channel 2.
CapturePlus II Key information calculated from the captured data and displayed is the SFDR, SINAD, S/D, and SNR. Notice that when running an averaged, multiple FFT test the user is not required to activate the Analyze FFT button to display the FFT graph. Only when capturing single data sets is the user required to activate the Analyze FFT button to display the FFT graph.
CapturePlus II APPENDIX B. RECOMMENDATIONS FOR MAXIMUM PERFORMANCE The following are some general recommendations for maximizing the performance of Cirrus Logic evaluation systems. – When applying power to the evaluation board, use power supplies isolated from utility AC line and ground. Isolated power supplies typically inject less electrical noise than non-isolated power supplies. – Connecting Analog Inputs 1. Route power supply and communications cables away from analog input cables. 2.
CapturePlus II APPENDIX C. FFT WINDOW LEAKAGE Windowing functions which are used to make FFT (Fast Fourier Transform) plots more informative also generate a measurable error by spreading energy from the FFT signal peaks to the surrounding noise floor. This results from an effect known as “window leakage”. The following table lists the windowing functions and their associated peak signal losses that are used by the Cirrus Logic CapturePlus II system.
CapturePlus II NOTES DS789UM2 41
CapturePlus II Contacting Cirrus Logic Support For all product questions and inquiries contact a Cirrus Logic Sales Representative. To find the one nearest to you go to www.cirrus.com IMPORTANT NOTICE Cirrus Logic, Inc. and its subsidiaries ("Cirrus") believe that the information contained in this document is accurate and reliable. However, the information is subject to change without notice and is provided "AS IS" without warranty of any kind (express or implied).
