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
MINIMUM PC/SYSTEM REQUIREMENTS
HOW TO INSTALL THE EVALUATION SOFTWARE
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\
Click
Next to view the installation review page
Click
Next to start the installation
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.

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

PROCEDURES FOR CONNECTING THE HARDWARE
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.
Place shunt to header JP1 to give +3.3V voltage out as seen in the label found in
SDP-PMD-IB1Z.
-
Connect the current meter in series with the Iout terminal block of the
EVAL-CN0179-PMDZ
Connect DC Power Supply (+18V/GND) to the Power connector P1.
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.
Plug in the wall wart and connect it to connector J1 of the
SDP-PMD-IB1Z.
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
Launch the executable found at C:\Program Files\Analog Devices\CN0179 and press the “Connect” button.
After pressing the “Connect” button, a prompt will appear informing the user if the SDP is already connected.
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:
Enter Hex Code – This control allows to Enter a value from 0x000 to 0x3FF.
Iout – This indicator shows the calculated Output Current depending on the input Code.
Data Bits – Binary equivalent of the Code loaded to the
AD5641 DAC.
VDAC – This indicator shows the calculated DAC output Voltage depending on the input code.
Enter Output Current – This control allows to Enter a value from 0 to 20.
Data Code – This indicator shows the Hex Code equivalent of the value loaded to the
AD5641 DAC.
Write DAC – When this button is pressed, the values/codes entered will send to the
AD5641 DAC via
SPI.
System Status String Indicator - This indicator displays a message to the user detailing the current state of the software.
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
SDP Board Information - provides details on the firmware version of the Blackfin used by the SDP board.
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