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This version (07 Mar 2014 20:46) was approved by JFitzger.

CN-0179 Software User Guide

OVERVIEW

The circuit is a 4 mA-to-20 mA current loop transmitter for communication between a process control system and its actuator. Besides being cost effective, this circuit offers the industry’s low power solution. The 4 mA-to-20 mA current loop has been used extensively in programmable logic controllers (PLCs) and distributed control systems (DCS’s), with digital or analog inputs and outputs. Current loop interfaces are usually preferred because they offer the most cost effective approach to long distance noise immune data transmission. The combination of low power AD8657 dual op amp, AD5641 DAC, and ADR02 reference allows more power budget for higher power devices, such as microcontrollers and digital isolators. The circuit output is 0 mA to 20 mA of current. The 4 mA to 20 mA range is usually mapped to represent the input control range from the DAC or micro-controller, while the output current range of 0 mA to 4 mA is often used to diagnose fault conditions.


GENERAL SETUP

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MINIMUM PC/SYSTEM REQUIREMENTS

  • One PC with the following
    • Windows XP SP2, Windows Vista or Windows 7 Business/Enterprise/Ultimate editions
    • Intel Pentium processor (x86 compatible), 1GHz or faster
    • 512 MB RAM and 2 GB available hard disk space
    • .NET 3.5 Framework

HOW TO INSTALL THE EVALUATION SOFTWARE

  1. Extract the file CN0179 Eval Software.zip and open the file setup.exe.

    NOTE: It is recommended that you install the CN0179 Evaluation Software to the default directory path C:\Program Files\Analog Devices\CN0179\ and all National Instruments products to C:\Program Files\National Instruments\

  2. Click Next to view the installation review page



  3. Click Next to start the installation



  4. Upon completion of the installation of the CN0179 Evaluation Software, the installer for the ADI SDP Drivers will execute.

    NOTE: It is recommended that you close all other applications before clicking “Next”. This will make it possible to update relevant system files without having to reboot your computer.





  5. Press “Next” to set the installation location for the SDP Drivers.

    It is recommended that you install the drivers to the default directory path
    C:\Program Files\Analog Devices\SDP\Drivers



  6. Press “Next” to install the SDP Drivers and complete the installation of all software. Click “Finish” when done.


PROCEDURES FOR CONNECTING THE HARDWARE

  1. Connect the 120-pin connector of the SDP-PMD-IB1Z circuit board to the connector marked “CON A” on the EVAL-SDP-CB1Z evaluation (SDP) board. Nylon hardware should be used to firmly secure the two boards, using the holes provided at the ends of the 120-pin connectors.
  2. Place shunt to header JP1 to give +3.3V voltage out as seen in the label found in SDP-PMD-IB1Z.
  3. Connect the 12-pin right angle male pin header of EVAL-CN0179-PMDZ to the 12-pin right angle female pin header of SDP-PMD-IB1Z.
  4. Connect the current meter in series with the Iout terminal block of the EVAL-CN0179-PMDZ
  5. Connect DC Power Supply (+18V/GND) to the Power connector P1.
  6. Plug the mini end of the USB cable into connector J1 of the EVAL-SDP-CB1Z and connect the other end of the USB cable into the Laptop or PC.
  7. Plug in the wall wart and connect it to connector J1 of the SDP-PMD-IB1Z.
  8. Place shunt to Header J1 to measure the voltage across the load on the Iout terminal block. No shunt means current measurement.

OPENING AND ENABLING THE EVALUATION SOFTWARE

  1. Launch the executable found at C:\Program Files\Analog Devices\CN0179 and press the “Connect” button.
  2. After pressing the “Connect” button, a prompt will appear informing the user if the SDP is already connected.
  3. Choose between two Operating Mode:
  • Normal Operation - DAC has normal current consumption of 100uA maximum. In this mode, DAC is able to start gathering data from the system and all the buttons found in the System Controls will be enabled.
  • Power Down Mode - The DAC’s current consumption falls to typically 0.5uA.DAC is tristated and cannot be able to acquire data from the system. (Note: DAC register are unaffected when in power down mode).

USING THE EVALUATION SOFTWARE

There are two ways to select the input control on the DAC; one is for setting the Output Current while the other is for setting the DAC CODE.


DESCRIPTIONS:

  1. Enter Hex Code – This control allows to Enter a value from 0x000 to 0x3FF.
  2. Iout – This indicator shows the calculated Output Current depending on the input Code.
  3. Data Bits – Binary equivalent of the Code loaded to the AD5641 DAC.
  4. VDAC – This indicator shows the calculated DAC output Voltage depending on the input code.
  5. Enter Output Current – This control allows to Enter a value from 0 to 20.
  6. Data Code – This indicator shows the Hex Code equivalent of the value loaded to the AD5641 DAC.
  7. Write DAC – When this button is pressed, the values/codes entered will send to the AD5641 DAC via SPI.
  8. System Status String Indicator - This indicator displays a message to the user detailing the current state of the software.
  9. System Status LED Indicator - This indicator displays the current state of the software in the form of an LED.
    There are three status LED colors:
    - Busy
    - Inactive
    - Error
  10. SDP Board Information - provides details on the firmware version of the Blackfin used by the SDP board.