EVAL-AD5933EBZ

Evaluation Board User Guide UG-364 One Technology Way • P.O. Box 9106 • Norwood, MA 02062-9106, U.S.A. • Tel: 781.329.4700 • Fax: 781.461.3113 • www.analog.com Evaluating the AD5933 1 MSPS, 12-Bit Impedance Converter Network Analyzer known frequency. The on-board ADC samples the response signal from the impedance, and an on-board DSP engine at each excitation frequency processes the DFT. The AD5933 also contains an internal temperature sensor with 13-bit resolution. The part operates from a 2.7 V to 5.5 V supply. Other on-board components include a ADR423 3.0 V reference to act as a stable supply voltage for the separate analog and digital sections of the device and a ADP3303 ultrahigh precision regulator to act as a supply to the on-board universal serial bus controller that interfaces to the AD5933. The user has the option to power the entire circuitry from the USB port of a computer. FEATURES Full-featured evaluation board for the AD5933 Graphic user interface software with frequency sweep capability for board control and data analysis Various power supply linking options Standalone capability with serial I2C loading from on-board microcontroller Selectable system clock options including internal RC oscillator or on-board 16 MHz crystal APPLICATIONS Electrochemical analysis Impedance spectroscopy Complex impedance measurement Corrosion monitoring and protection equipment Biomedical and automotive sensors Proximity sensing The evaluation board also has a high performance trimmed 16 MHz surface-mount crystal to act as a system clock to the AD5933, if required. The various link options located around the evaluation board are listed in Table 1. Interfacing to the AD5933 is through a USB microcontroller that generates the I2C signals necessary to communicate with the AD5933. Interfacing to the USB microcontroller is done through a Visual Basic® graphic user interface located on and run from the PC. Complete specifications for the AD5933 are available in the AD5933 data sheet available from Analog Devices, Inc., and should be consulted in conjunction with this user guide when using the evaluation board. GENERAL DESCRIPTION This user guide describes the EVAL-AD5933EBZ evaluation board, and the application software developed to interface with the device. The AD5933 is a high precision impedance converter system that combines an on-board frequency generator with a 12-bit, 1 MSPS analog-to-digital converter (ADC). The frequency generator allows an external complex impedance to be excited with a EVALUATION BOARD BLOCK DIAGRAM 1.98V p-p VDD MCLK AVDD VDD 1.98V p-p 1.48V VDD/2 DVDD VDD VDD − DDS CORE (27 BITS) OSCILLATOR DAC ROUT SCL SDA I2C INTERFACE REAL REGISTER + 47nF 50kΩ TRANSMIT SIDE OUTPUT AMPLIFIER TEMPERATURE SENSOR ZUNKNOWN A1, A2 ARE ½ AD8606 AD5933 IMAGINARY REGISTER A1 50kΩ VOUT RFB RFB 1024-POINT DFT 20kΩ GAIN I-V LPF VDD/2 AGND DGND − A2 + VDD 50kΩ 50kΩ Figure 1. PLEASE SEE THE LAST PAGE FOR AN IMPORTANT WARNING AND LEGAL TERMS AND CONDITIONS. 20kΩ Rev. 0 | Page 1 of 28 10441-001 VIN ADC (12 BITS) UG-364 Evaluation Board User Guide TABLE OF CONTENTS Features .............................................................................................. 1  Performing a Frequency Sweep...................................................6  Applications....................................................................................... 1  Two Installation Frequently Asked Questions ....................... 10  General Description ......................................................................... 1  Source Code for Impedance Sweep.............................................. 12  Evaluation Board Block Diagram................................................... 1  Evaluation Board Source Code Extract................................... 13  Revision History ............................................................................... 2  Gain Factor Calculation ............................................................ 17  Evaluation Board Hardware ............................................................ 3  Temperature Measurement ....................................................... 17  Terminal Block Functions ........................................................... 3  Impedance Measurement Tips ................................................. 18  Getting Started .................................................................................. 4  Evaluation Board Schematics and Artwork................................ 23  Setup Sequence Summary ........................................................... 4  Ordering Information.................................................................... 26  Installing the Software ................................................................. 4  Bill of Materials........................................................................... 26  Connecting the USB Cable.......................................................... 5  Related Links............................................................................... 27  Verifying the Links and Power Up the Evaluation Board....... 6  REVISION HISTORY 2/12—Revision 0: Initial Version Rev. 0 | Page 2 of 28 Evaluation Board User Guide UG-364 EVALUATION BOARD HARDWARE TERMINAL BLOCK FUNCTIONS Table 1. Link Functions Link No. LK1 LK2 LK3 LK4 LK5 LK6 Default Location Out Out In Out In A Function Option to remove external conditioning Option to remove external conditioning On-board, 16 MHz crystal connection, connects to Y2 SMB connected external clock Connects 5 V from USB to ADP3303 AVDD and DVDD power supply connector Rev. 0 | Page 3 of 28 UG-364 Evaluation Board User Guide GETTING STARTED SETUP SEQUENCE SUMMARY 1. 2. 3. 4. Install the AD5933 graphical user interface software on the CD that accompanies the evaluation board. Do not connect the USB cable from the AD5933 evaluation board to the computer USB hub until the evaluation software is properly installed. See the Installing the Software section for additional information. Connect the computer USB port to the evaluation board using the USB cable provided in the evaluation kit and run the USB hardware installation wizard after the evaluation software is correctly installed (the hardware installation may happen automatically depending on the settings of the current operating system). See the Connecting the USB Cable section for additional information. Ensure that the appropriate links are made throughout the evaluation board. Prior to opening and running the evaluation software program, power up the evaluation board appropriately. See the Verifying the Links and Power Up section for additional information. Configure the front panel of the evaluation board software to run the required sweep function. See the Performing a Frequency Sweep section for additional information. 10441-004 The evaluation board installation instructions are for the Windows XP® operating system with English (United States) set for its language. The regional and language settings of a PC can be changed in the Regional and Language directory within the Control Panel (Start/Control Panel/Regional and Language/ Formats). The installation consists of the following steps that are described in detail in the sections that follow. Figure 3. Installation Wizard 3. Install the evaluation board software in the default destination folder path, C:\Program Files\Analog Devices\AD5933\ AD5933 Evaluation Software Rev 1.0 Setup (see Figure 4). INSTALLING THE SOFTWARE 2. Put the evaluation board CD into the CD drive of the PC and click Start/My Computer. The CD software installation may happen automatically after the CD is inserted into the CD drive; however, this may depend on the settings of the current operating system. If the software installation does not automatically start, go to AD5933 Installation/Setup.exe and double-click Setup.exe to install the software on the PC through the installation wizard (see Figure 2 and Figure 3). 10441-003 1. Figure 2. Evaluation Software CD Contents Rev. 0 | Page 4 of 28 10441-005 To install the evaluation board software, use the following steps: Figure 4. Default Destination Folder Evaluation Board User Guide Choose the Analog Devices directory (see Figure 5). If the Analog Devices folder does not yet exist, create an Analog Devices folder and add the program icon to this new folder. CONNECTING THE USB CABLE To connect the USB cable, use the following steps: 1. Plug the USB cable into the USB hub of the PC and connect the other end of the USB cable into the AD5933 evaluation board USB socket (see J1 in Figure 32). A message may appear that a USB device has been detected on the host computer and that new hardware has been found (see Figure 8). 10441-006 10441-009 4. UG-364 Figure 8. USB Device Detected by Host Computer 2. Figure 5. Select Analog Devices Directory 10441-007 Figure 6. Opening the Evaluation Software The following message appears (see Figure 7) because the firmware code that the evaluation software operates from, and that needs to be downloaded to the evaluation board USB microcontroller memory each time the interface software program is opened, cannot be successfully downloaded to the evaluation board. The error message is presented because there is currently no USB connection between the computer and the AD5933 evaluation board at this stage; therefore, this error message is to be expected. Click Cancel. 10441-010 6. After installing the software, remove the CD from the CD drive. You may be asked to reboot the computer at this stage. Go to Start/All Programs/Analog Devices/AD5933/ AD5933 (see Figure 6). Figure 9. Hardware Installation Wizard 10441-008 5. The Found New Hardware Wizard then appears (see Figure 9). This wizard locates and installs the appropriate driver files for the AD5933 evaluation kit in the operating system registry. Select Install the software automatically (Recommended) and click Next > to continue (see Figure 9). Figure 7. Expected Error Message Rev. 0 | Page 5 of 28 UG-364 3. Evaluation Board User Guide A standard windows operating system warning message then appears, as shown in Figure 10. It indicates that the new hardware currently being installing on the Windows® operating system (AD5933 evaluation kit) has not passed the Windows logo testing to verify compatibility with Windows XP. This warning appears because the installation is an evaluation setup installation and is not intended to be used in a production environment. Click Continue Anyway and then click Finish. PERFORMING A FREQUENCY SWEEP The sequence for performing a linear frequency sweep across a 200 kΩ resistive impedance connected across the VOUT and VIN pins within the frequency range of 30 kHz to 30.2 kHz is outlined in this section. The default software settings for the evaluation board are shown in Figure 12. (Note that a 200 kΩ resistor must be connected across the VIN and VOUT pins of the AD5933). The default link positions are outlined in Table 1, see this before continuing. To open the software, go to Start > Programs > Analog Devices > AD5933 and click AD5933 Evaluation Software. Figure 12 shows the graphic user interface program open and running successfully. It also shows the interface panel along with a frequency sweep impedance profile for a 200 kΩ resistive impedance (note RFB = 200 kΩ). To setup a typical sweep across a 200 kΩ impedance (RFB = 200 kΩ), use the following steps: • 10441-011 • Figure 10. Expected Warning Message • 10441-012 The message shown in Figure 11 appears once the hardware has been successfully installed. • Figure 11. Successful Hardware Installation VERIFYING THE LINKS AND POWER UP THE EVALUATION BOARD Ensure that the relevant links are in place on the evaluation board (see Table 1) and that the proper power connections and supply values have been made to the terminal blocks before applying power to the evaluation board. The power supply terminal blocks are outlined in evaluation board schematic (see Figure 32). Note that the USB connector only supplies power to the Cypress USB controller chip that interfaces to the AD5933. If required, a dedicated external voltage supply to each terminal block can be provided. Ensure that all relevant power supply connections and links are made before running the evaluation software. For optimum performance, supply the three supply signals (AVDD1, AVDD2, and DVDD) from a stable external reference supply via the power supply terminal blocks on the board. Rev. 0 | Page 6 of 28 Set Start Frequency (Hz) to 30000 (Hz) within the Sweep Parameters section (see 1 in Figure 12). The start frequency is 24-bit accurate. Set Delta Frequency (Hz) to 2 (Hz) within the Sweep Parameters section (see 1 in Figure 12). The frequency step size is also 24-bit accurate. Set Number Increments (9 Bit) within the Sweep Parameters section to 200 (see 1 in Figure 12) to set the number of increments along the sweep to 200. The maximum number of increments that the device can sweep across is 511, and the value is stored in a register as a 9-bit value. Set Number of Settling Time Cycles to 15 (see 1 in Figure 12). Note that when sweeping across a high-Q structure, such as resonant impedance, users must ensure that the contents of the settling time cycles register is sufficient to ensure that the impedance under test settles before incrementing between each successive frequency in the programmed sweep. This is achieved by increasing the Number of Settling Time Cycles value. The delay between the time a frequency increment takes place on the output of the internal direct digital synthesizer (DDS) core and the time the ADC samples the response signal at this new frequency is determined by the contents of the number of settling time cycles registers (Register 0x8A and Register 0x8B), see the AD5933 data sheet for further details. For example, if a value of 15 is programmed into the Number of Settling Time Cycles box, and if the next output frequency is 32 kHz, the delay between the time the DDS core starts to output the 32 kHz signal and the time the ADC samples the response signal is 15 × (1/32 kHz) ≈ 468.7 μs. The maximum number of settling time cycle delays that can be programmed to the board is 511 cycles. The value is stored in a register as a 9-bit value, and this value can be further multiplied by a factor of 2 or by a factor of 4. Evaluation Board User Guide 2 3 4 5 10441-013 1 UG-364 Figure 12. AD5933 Evaluation Software Front Panel (Impedance Profile of 200 kΩ Resistor Displayed) • • • • Choose the external clock as the system clock. Select External clock in the System Clock section (see 2 in Figure 12). Set Output Excitation voltage range of the AD5933 at Pin 6 (VOUT) to Range1:2v p-p (see 2 in Figure 12). The four possible output ranges available are 2 V p-p, 1 V p-p, 0.4 V p-p, or 0.2 V p-p, typically. Set the PGA gain of the ADC on the receive stage (either ×1 or ×5) in the PGA Control section to ×1 (see 2 in Figure 12). Refer to the Calibration Impedance panel (see 2 in Figure 12). Prior to making any measurements, calibrate the AD5933 with a known (that is, accurately measured) calibration impedance connected between the VIN and VOUT pins of the AD5933. The choice of calibration impedance topology (for example, R1 in series with C1, R1 in parallel with C1) depends on the application in question. However, ensure that each component of the measured calibration impedance is entered correctly into each chosen topology component text box (see 2 in Figure 12). For this example, Resistor • • • Rev. 0 | Page 7 of 28 only R1 was chosen in the Calibration Impedance section, that is, to measure the impedance of a 200 kΩ resistive impedance across frequency. Also for this example, set Resistor value R1 to 200E3 (Ω). Click Program Device Registers (see 3 in Figure 12) to program the sweep parameters as previously chosen into the appropriate on-board registers of the AD5933 through the I2C interface. The value programmed into the settling time cycles can be further multiplied by a factor of 2 or a factor of 4 for a sweep. Select ×1 (Default) in the DDS Settling Time Cycles section. Now that the frequency sweep parameters and gain settings are programmed, the next step is to calibrate the AD5933 system by calculating the gain factor. The explanation of the system calibration gain factor, a term calculated once at system calibration, is provided in detail in the AD5933 data sheet. The AD5933 gain factor must be calibrated correctly for a particular impedance range before any subsequent valid impedance measurement (refer to the AD5933 data sheet for further details). UG-364 • Evaluation Board User Guide To automatically calculate the gain factor(s) for the subsequent sweep, click Calculate Gain Factor. The evaluation software evaluates either a single midpoint frequency gain factor or multipoint frequency gain factors, that is, a gain factor for each point in the programmed sweep (see 4 in Figure 12). The midpoint gain factor is determined at the midpoint of the programmed sweep, and the multipoint gain factors are determined at each point in the programmed frequency sweep. • • When either the midpoint gain factor or the multipoint gain factors are calculated, a message appears on the evaluation board software front panel, as shown in Figure 13. The gain factor(s) returned to the evaluation software are subsequently used for the sweep across the impedance under test. Click Measure in the Internal Temperature section of the evaluation board software front panel to take a reading from the on-board temperature sensor. This returns the 13-bit temperature of the device. See AD5933 data sheet for more information on the temperature sensor. Click Download Impedance Data to download the frequency sweep data (that is, frequency, impedance phase, real, imaginary, and magnitude data) from the DFT of the sweep (see 5 in Figure 12). The common dialog front panel is presented as shown in Figure 15. Choose a file name in a directory of choice and click Save (see Figure 15). This saves the sweep data to a comma separated variable file (.CSV) located in the chosen directory. 1. CHOOSE DIRECTORY 3. SAVE THE FILE Figure 13. Confirmation of a Midpoint Calculation or a Multipoint Gain Factors Calculation Figure 15. Saving the Sweep Data 10441-015 Note that should any of the system gain settings (for example, change in output excitation range or PGA gain) change after the system is calibrated (that is, gain factor(s) are calculated), it is necessary to recalculate the gain factor(s) to subsequently measure accurate impedance results. The gain factor(s) calculated in the software are not programmed into the AD5933 RAM and are only valid when the evaluation software program is open and running. The gain factor(s) are not retained in the evaluation software when the software program is closed. Click Start Sweep (see 5 in Figure 12) to begin the sweep. Once the evaluation software completes the sweep, it automatically returns both a plot of the impedance vs. frequency and phase vs. frequency for the impedance under test (see Figure 12).The progress of the sweep is outlined with a progress bar, as shown in Figure 14. Figure 14. Sweep Progress Bar (Blue) Rev. 0 | Page 8 of 28 The contents of this file can be accessed by using Notepad or Microsoft Excel to plot the data. Each file contains a single column of data. The format of the downloaded data is shown in Figure 16. 10441-017 After the system interface software calculates the gain factor(s) for the programmed sweep parameters, the results are shown in the Calculated Gain Factor box. • 10441-016 10441-014 2. CHOOSE FILE NAME Figure 16. Opening the Sweep Data in Excel Evaluation Board User Guide UG-364 Each data entry corresponds to a single measurement (frequency) point; therefore, if the value for the number of increments is programmed as 511 point, the array contains a single column of data with 512 data points, starting at the start frequency and ending at stop frequency value, which is determined by Start Frequency + (Number of Increments × Delta Frequency) 10441-018 The impedance profile and phase profile vs. frequency appears in the evaluation software front panel after the sweep has completed. Click the individual tabs to switch between Absolute Impedance |Z| and Impedance Phase Ø. Click Absolute Impedance |Z| to show how the impedance under analysis (ZUNKNOWN) varies across the programmed frequency range. To view how the phase across the network under analysis varies, click Impedance Phase Ø, as shown in Figure 17. Note that the phase measured by the AD5933 takes into account the phase introduced through the entire signal path, that is, the phase introduced through the output amplifiers, receive current-to-voltage (I-V) amplifier, and the low-pass filter, along with the phase through the impedance (ZØ) under analysis connected between VOUT and VIN (Pin 6 and Pin 5 of the AD5933). Calibrate out the phase of the system using a resistor before any subsequent impedance (ZØ) phase measurement is calculated. Calibrate with a resistor in the evaluation software to calibrate the system phase correctly (refer to the Impedance Measurement Tips section for further details). Figure 17. The Phase Tab on the AD5933 Evaluation Software Front Panel, Phase of 200 kΩ Resistor (0°) Displayed Rev. 0 | Page 9 of 28 UG-364 Evaluation Board User Guide 3. TWO INSTALLATION FREQUENTLY ASKED QUESTIONS Scroll to Universal Serial Bus controllers and expand the root directory (see Figure 19). When the AD5933 hardware is correctly installed, each time the USB cable connecting the evaluation board to the computer is plugged in, the items within the Universal Serial Bus controllers are refreshed. Q: How can I confirm that the hardware was correctly installed on the PC? A: To confirm the hardware was correctly installed on the PC, use the following steps: Right-click My Computer and left-click Properties. Go to the Hardware tab, and click Device Manager (see Figure 18). EXPAND ROOT DIRECTORY 10441-019 Figure 18. System Properties 10441-020 1. 2. Figure 19 shows what to expect when the AD5933 evaluation board is correctly installed and when the evaluation board and USB cable are connected correctly to the computer. The root directory is subsequently refreshed when the USB cable is unplugged from evaluation board, and the AD5933 evaluation kit icon is removed from the main root. Figure 19. Correctly Installed Hardware Rev. 0 | Page 10 of 28 Evaluation Board User Guide UG-364 Q: During installation, when the board is plugged in for the first time, the message shown in Figure 20 appears. When I click Finish, the message shown in Figure 21 appears. What do I do next? 2. RIGHT CLICK ON THIS DEVICE 10441-023 1. EXPAND THIS DIRECTORY 10441-021 Figure 22. USB Device Not Recognized 10441-022 Figure 20. Error During the Hardware Installation Figure 21. Found New Hardware Issue A: If the evaluation software is installed correctly (install the software correctly prior to plugging in the board for the first time), this message simply indicates that the AD5933 device drivers have not been installed to the correct registry and, therefore, could not be correctly located by the install wizard. CORRECTLY INSTALLED HARDWARE 1. 2. 3. 4. 5. Right-click My Computer, and left-click Properties. Go to the Hardware tab, select Device Manager, and expand Other devices (see Figure 22). The computer has not recognized the USB device, that is, the AD5933 evaluation board. Right-click USB Device and select Uninstall Driver. Unplug the evaluation board and wait approximately 30 seconds before plugging it in again. Proceed through the installation wizard a second time. The expanded root directory shown in Figure 19 is a correct installation. If the same error message is encountered the second time, uninstall the device driver, uninstall the software, and contact Analog Devices applications support at www.analog.com for further instructions regarding valid driver files. Rev. 0 | Page 11 of 28 10441-024 To reinstall the device drivers, use the following steps: Figure 23. Correctly Installed Hardware UG-364 Evaluation Board User Guide SOURCE CODE FOR IMPEDANCE SWEEP PROGRAM FREQUENCY SWEEP PARAMETERS INTO RELEVANT REGISTERS (1) START FREQUENCY REGISTER (2) NUMBER OF INCREMENTS REGISTER (3) FREQUENCY INCREMENT REGISTER PLACE THE AD5933 INTO STANDBY MODE. RESET: BY ISSUING A RESET COMMAND TO THE CONTROL REGISTER, THE DEVICE IS PLACED IN STANDBY MODE. PROGRAM THE INITIALIZE WITH START FREQUENCY COMMAND TO THE CONTROL REGISTER. AFTER A SUFFICIENT AMOUNT OF SETTLING TIME HAS ELAPSED, PROGRAM THE START FREQUENCY SWEEP COMMAND IN THE CONTROL REGISTER. POLL THE STATUS REGISTER TO CHECK IF THE DFT CONVERSION IS COMPLETE. N Y PROGRAM THE INCREMENT FREQUENCY OR THE REPEAT FREQUENCY COMMAND TO THE CONTROL REGISTER. READ VALUES FROM THE REAL AND IMAGINARY DATA REGISTER. Y POLL THE STATUS REGISTER TO CHECK IF FREQUENCY SWEEP IS COMPLETE. N PROGRAM THE AD5933 INTO POWER-DOWN MODE. 10441-025 Y Figure 24. Sweep Flow Outline This section outlines the evaluation board code structure required to set up the AD5933 frequency sweep. The sweep flow outline is shown in Figure 24. Each section of the flow diagram is explained with the help of the visual basic code extracts. The firmware code (c code), which is downloaded to the USB microcontroller connected to the AD5933, implements the low level I2C signal control (that is, read and write vendor request). The code extract, which is shown in the Evaluation Board Source Code Extract section, shows how to program a single frequency sweep starting at 30 kHz, with a frequency step of 10 Hz and with 150 points in the sweep. The code assumes that a 16 MHz clock signal is connected to Pin 8 (MCLK) of the AD5933. The impedance range under test is from 90 kΩ to 110 kΩ. The gain factor is calculated at the midpoint of the frequency sweep, that is, 30.750 kHz. The calibration is carried out with a 100 kΩ resistor connected between VOUT and VIN. The feedback resistor = 100 kΩ. The first step in Figure 24 is to program the three sweep parameters necessary to define the frequency sweep (that is, the start frequency, number of increments, and frequency increments). Refer to the AD5933 data sheet for more details. Rev. 0 | Page 12 of 28 Evaluation Board User Guide UG-364 EVALUATION BOARD SOURCE CODE EXTRACT ‘------------------------------------------------------------------------------------------------------‘Code developed using visual basic® 6. ‘Datatype range ‘Byte 0-255 ‘Double -1.797e308 to – 4.94e-324 and 4.94e-324 to 1.7976e308 ‘Integer -32,768 to 32767 ‘Long -2,147,483,648 to 2,147,483,647 ‘Variant‘...when storing numbers same range as double. When storing strings same range as string. ‘-------------------------------------- Variable Declarations ----------------------------------------Dim ReadbackStatusRegister As Long 'stores the contents of the status register. Dim RealData As Double 'used to store the 16 bit 2s complement real data. Dim RealDataUpper As Long 'used to store the upper byte of the real data. Dim RealDataLower As Long 'used to store the lower byte of the real data. Dim ImagineryData As Double 'used to store the 16 bit 2s complement real data. Dim ImagineryDataLower As Long 'used to store the upper byte of the imaginary data. Dim ImagineryDataUpper As Long 'used to store the lower byte of the imaginary data. Dim Magnitude As Double 'used to store the sqrt (real^2+imaginary^2). Dim Impedance As Double 'used to store the calculated impedance. Dim MaxMagnitude As Double 'used to store the max impedance for the y axis plot. Dim MinMagnitude As Double 'used to store the min impedance for the y axis plot. Dim sweep_phase As Double 'used to temporarily store the phase of each sweep point. Dim Frequency As Double 'used to temporarily store the current sweep frequency. Dim Increment As Long 'used as a temporary counter Dim i As Integer 'used as a temporary counter in (max/min) mag,phase loop Dim xy As Variant 'used in the stripx profile Dim varray As Variant Dim Gainfactor as double ‘either a single mid point calibration or an array of calibration points Dim TempStartFrequency As Double Dim StartFrequencybyte0 As Long Dim StartFrequencybyte2 As Long Dim StartFrequencybyte1A As Long Dim StartFrequencybyte1B As Long Dim DDSRefClockFrequency As Double Dim NumberIncrementsbyte0 As Long Dim NumberIncrementsbyte1 As Long Dim FrequencyIncrementbyt0 As Long Dim FrequencyIncrementbyt1 As Long Dim FrequencyIncrementbyt2 As Long Dim SettlingTimebyte0 As Long Dim SettlingTimebyte1 As Long ‘-------------------------------------- I^2C read/write definitions----------------------------------------‘used in the main sweep routine to read and write to AD5933.This is the vendor request routines in the firmware Private Sub WritetToPart(RegisterAddress As Long, RegisterData As Long) PortWrite &HD, RegisterAddress, RegisterData ‘parameters = device address register address register data End Sub Public Function PortWrite(DeviceAddress As Long, AddrPtr As Long, DataOut As Long) As Integer PortWrite = VendorRequest(VRSMBus, DeviceAddress, CLng(256 * DataOut + AddrPtr), VRWRITE, 0, 0) End Function Public Function PortRead(DeviceAddress As Long, AddrPtr As Long) As Integer PortRead = VendorRequest(VRSMBus, DeviceAddress, AddrPtr, VRREAD, 1, DataBuffer(0)) PortRead = DataBuffer(0) End Function ‘------------------------------------- PHASE CONVERSION FUNCTION DEFINITION -------------------------------‘This function accepts the real and imaginary data(R, I) at each measurement sweep point and converts it to a degree ‘----------------------------------------------------------------------------------------------------------Public Function phase_sweep (ByVal img As Double, ByVal real As Double) As Double Dim theta As Double Dim pi As Double pi = 3.141592654 If ((real > 0) And (img > 0)) Then theta = Atn(img / real) phase2 = (theta * 180) / pi ' theta = arctan (imaginary part/real part) 'convert from radians to degrees Rev. 0 | Page 13 of 28 UG-364 Evaluation Board User Guide ElseIf ((real > 0) And (img < 0)) Then theta = Atn(img / real) phase2 = ((theta * 180) / pi ) +360 '4th quadrant theta = minus angle ElseIf ((real < 0) And (img < 0)) Then theta = -pi + Atn(img / real) phase2 = (theta * 180) / pi '3rd quadrant theta img/real is positive ElseIf ((real < 0) And (img > 0)) Then theta = pi + Atn(img / real) phase2 = (theta * 180) / pi '2nd quadrant img/real is neg End If End Function ‘----------------------------------------------------------------------------------------------------------Private Sub Sweep () ’ the main sweep routine ‘This routine coordinates a frequency sweep using a mid point gain factor (see datasheet). 'The gain factor at the mid-point is determined from the real and imaginary contents returned at this mid ‘point frequency and the calibration impedance. 'The bits of the status register are polled to determine when valid data is available and when the sweep is ‘complete. '----------------------------------------------------------------------------------------------------------IndexArray = 0 'initialize counter variable. Increment = NumberIncrements + 1 'number of increments in the sweep. Frequency = StartFrequency 'the sweep starts from here. ‘------------------------- PROGRAM 30K Hz to the START FREQUENCY register --------------------------------DDSRefClockFrequency = 16E6 StartFrequency = 30E3 ‘Assuming a 16M Hz clock connected to MCLK ‘frequency sweep starts at 30K Hz TempStartFrequency = (StartFrequency / (DDSRefClockFrequency / 4)) * 2^27 ‘dial up code for the DDS TempStartFrequency = Int(TempStartFrequency) ‘30K Hz = 0F5C28 hex StartFrequencybyte0 = 40 StartFrequencybyte1 = 92 StartFrequencybyte2 = 15 ‘40 DECIMAL = 28 HEX ‘92 DECIMAL = 5C HEX ’15 DECIMAL = 0F HEX 'Write in data to Start frequency register WritetToPart &H84, StartFrequencybyte0 '84 hex lsb WritetToPart &H83, StartFrequencybyte1 '83 hex WritetToPart &H82, StartFrequencybyte2 '82 hex ‘--------------------------------- PROGRAM the NUMBER OF INCREMENTS register -----------------------------‘The sweep is going to have 150 points 150 DECIMAL = 96 hex 'Write in data to Number Increments register WritetToPart &H89, 96 ‘lsb WritetToPart &H88, 00 ‘msb ‘--------------------------------- PROGRAM the FREQUENCY INCREMENT register -----------------------------‘The sweep is going to have a frequency increment of 10Hz between successive points in the sweep DDSRefClockFrequency = 16E6 FrequencyIncrements = 10 ‘Assuming a 16M Hz clock connected to MCLK ‘frequency increment of 10Hz TempStartFrequency = (FrequencyIncrements / (DDSRefClockFrequency / 4)) * 2^27 ‘dial up code for the DDS TempStartFrequency = Int(TempStartFrequency) ’10 Hz = 335 decimal = 00014F hex FrequencyIncrementbyt0 = 4F FrequencyIncrementbyt1 = 01 FrequencyIncrementbyt2 = 00 ‘335 decimal = 14f hex 'Write in data to frequency increment register WritetToPart &H87, FrequencyIncrementbyt0 '87 hex lsb WritetToPart &H86, FrequencyIncrementbyt1 '86 hex WritetToPart &H85, FrequencyIncrementbyt2 '85 hex msb ‘--------------------------------- PROGRAM the SETTLING TIME CYCLES register -----------------------------‘The DDS is going to output 15 cycles of the output excitation voltage before the ADC will start sampling ‘the response signal. The settling time cycle multiplier is set to x1 Rev. 0 | Page 14 of 28 Evaluation Board User Guide UG-364 SettlingTimebyte0 = 0F ‘15 cycles (decimal) = 0F hex SettlingTimebyte1 = 00 ’00 = X1 WritetToPart &H8B, SettlingTimebyte0 WritetToPart &H8A, SettlingTimebyte1 ‘-------------------------------------- PLACE AD5933 IN STANDBYMODE ---------------------------------------‘Standby mode command = B0 hex WritetToPart &H80, &HB0 '------------------------- Program the system clock and output excitation range and PGA setting----------‘Enable external Oscillator WritetToControlRegister2 &H81, &H8 ‘Set the output excitation range to be 2vp-p and the PGA setting to = x1 WritetToControlRegister2 &H80, &H1 ‘----------------------------------------------------------------------------------------------------------‘------------- ------------ Initialize impedance under test with start frequency --------------------------'Initialize Sensor with Start Frequency WritetToControlRegister &H80, &H10 msDelay 2 'this is a user determined delay dependent upon the network under analysis (2ms delay) ‘-------------------------------------- Start the frequency sweep -----------------------------------------'Start Frequency Sweep WritetToControlRegister &H80, &H20 'Enter Frequency Sweep Loop ReadbackStatusRegister = PortRead(&HD, &H8F) ReadbackStatusRegister = ReadbackStatusRegister And &H4 ' mask off bit D2 (i.e. is the sweep complete) Do While ((ReadbackStatusRegister 4) And (Increment 0)) 'check to see if current sweep point complete ReadbackStatusRegister = PortRead(&HD, &H8F) ReadbackStatusRegister = ReadbackStatusRegister And &H2 'mask off bit D1 (valid real and imaginary data available) ‘------------------------------------------------------------------------If (ReadbackStatusRegister = 2) Then ' this sweep point has returned valid data so we can proceed with sweep Else Do ‘if valid data has not been returned then we need to pole stat reg until such time as valid data 'has been returned ‘i.e. if point is not complete then Repeat sweep point and pole status reg until valid data returned WritetToControlRegister &H80, &H40 'repeat sweep point Do ReadbackStatusRegister = PortRead(&HD, &H8F) ReadbackStatusRegister = ReadbackStatusRegister And &H2 ' mask off bit D1- Wait until dft complete Loop While (ReadbackStatusRegister 2) Loop Until (ReadbackStatusRegister = 2) End If '------------------------------------------------------------------------- ' RealDataUpper = PortRead(&HD, &H94) RealDataLower = PortRead(&HD, &H95) RealData = RealDataLower + (RealDataUpper * 256) 'The Real data is stored in a 16 bit 2's complement format. 'In order to use this data it must be converted from 2's complement to decimal format If RealData