Run the Demonstration (AD7768‐1)

Run the Demonstration

Table of Contents

1. Signal source
2. Run the demonstration locally
3. Run the demonstration via ethernet

Signal Source

The AD7768-1 requires a Differential signal from a signal source. AD7768-1 accepts input voltage from AVSS to AVDD1 centered around VCM=(AVDD1-AVSS)/2, and differential input full swing equal to Vref, above which ADC conversion will saturate. The AD7768-1, in its default configuration, is setup with Vref equal to 4.096V, VDD equal to 5V & VSS equal to GND. VSS can be changes to -2.5V from onboard GAVSSA or through external supply. So by default AD7768-1 requires the input signal to be centered around VCM equal to 2.5V which can be externally given through VCM input on AD7768-1-FMCZ. Connect the Differential signal source to VIN+ and VIN- input of AD7768-1. Give external noise free variable VCM supply to VCM input & adjust it in range 2V to 3.5V for better output. A single ended signal generator with 2 outputs can be used to generate the differential signals driving the AD7768-1 inputs.

• Set up the first channel to generate the desired signal
• Set up the second channel for tracking the first channel
• Offset both channels with VCOM.

However, the EVAL-AD7768-1FMCZ board is set up to use the ADA4807 buffers which offset the inputs by VCOM. VCOM starts out as an output (VCM_OUT) from the AD7768-1 at (AVDD1-AVSS)/2 and goes through select jumpers (0 ohm resistors) VCM, and unity gain voltage follower as seen below. This means that the user is expected to provide a true differential input centered at AVSS, and the VCOM takes care of shifting it up.

By default, VCM is set to position A.

Run the demonstration locally

Power up the unit using this hardware configuration. Wait approximately 60 seconds for the unit to be fully functional.

IIO Oscilloscope will be automatically launched on the system desktop. No configuration is required.

Enable voltage0 ADC channel

Select a Plot Channel to be displayed in IIO Oscilloscope. Click on the check box in the Plot Channel window adjacent to voltage0

Capture Time Domain Signals

Press the Capture / Stop button to begin the capture process.

Capture Frequency Domain Signals with Frequency Markers enabled

Change the capture mode to Frequency Domain. Select an FFT Size and Average. Press the Capture / Stop button to begin the capture process.

Right click in the IIO Oscilloscope plot area. Select a marker option. Press the Capture / Stop button to begin the capture process with markers.

Note the information in the Marker window. This capture shows a signal source of 1 khz with harmonic components.

Shutting down the demo

• Power down the target. Launch a Root Terminal. Type the following

    $ poweroff  
  

• Wait 30 seconds and then you can safely power down the DataStorm DAQ

Run the demonstration via ethernet

Define the host PC IP address

A wired ethernet point to point connection between the host PC and the embedded target is required. Use this link for instructions on how to assign a static IP address to the host Ethernet adapter. Set the following values

• IP address : 192.168.0.1

• Subnet mask : 255.255.255.0

• No entries required for the other fields

Connect to the target terminal

• A wired Micro USB serial port connection between the host PC and the embedded target is required
• Launch a linux terminal (like Tera Term VT or Putty) and connect using serial port
• Select 115200 baud
• Select the appropriate target COM port

Define the target IP address

Type the following at the terminal prompt to set the target IP address

• $ ifconfig eth0 192.168.0.2 up

Launch IIO Oscilloscope

Note: IIO Oscilloscope creates a .osc_profile.ini file in the Users/UserName/Appdata/Local directory. The next time IIO Oscilloscope is opened, the existence of this file delays connection to the target. It is recommended to delete the .osc_profile.ini (if it exists) prior to launching IIO Oscilloscope.

Connect to the target

• Select the Remote Devices option and enter the IP address 192.168.0.2 and click the Refresh button..
• A successful connection results in discovery of the IIO devices. Press OK to continue.

Enable voltage0 ADC channel

Select a Plot Channel to be displayed in IIO Oscilloscope. Click on the check box in the Plot Channel window adjacent to voltage0

Capture Time Domain Signals

Press the Capture / Stop button to begin the capture process.

Capture Frequency Domain Signals

Change the capture mode to Frequency Domain. Select an FFT Size and Average. Press the Capture / Stop button to begin the capture process.

Enable Frequency Markers

Right click in the IIO Oscilloscope plot area. Select a marker option. Press the Capture / Stop button to begin the capture process with markers.

Note the information in the Marker window.

Shutting down the demo

• Power down the target. Type the following at the terminal prompt

    $ poweroff  
  

• Wait until the linux terminal shows

    $ reboot : System Halted
  

• Close out IIO Oscilloscope and all associated windows

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