SetUp Menu


Detector calibration

Menu "SetUP/Calibrate Detector" allows the user to enter a positive or negative offset voltage that is added to the sample read from the AD/C.

Different areas can be identified:

  1. Select "View/Table" and "Scale/Linear".
  2. Connect the input of the detector to a known voltage
  3. Adjust the offset until the right voltage is presented.
  4. Every time you 'Apply', table and graph will be updated with the new offset

The algorithm implemented is: Volt = Sample * Step + offset

Frequency generator calibration

Menu "SetUP/Calibrate Generator" allows the user to enter a positive or negative offset to the frequency generated by the DDS.

  1. Select any start frequency.
  2. Connect the output of the generator to a frequency meter.
  3. Adjust the offset until the meter shows the right start frequency.
  4. Apply

This offset is a number that is used to calculate the command word sent to the DDS:

For the AD9951 the word is the rounded result of:
Frequency * (2 ^ 32/(Xtal Frequency * Multiplier)+Offset)

For the AD9851 when the 6xREFCLK is engaged, the word sent is:
Frequency * (2 ^ 32/(Xtal Frequency * 6) + Offset)

or

Frequency * (2 ^ 32/ Xtal Frequency + Offset)
if the 6xREFCLK is disabled

Program configuration

First time program is launched, user is request to select the interface where the DDS generator and the other devices are connected.

  1. Choose the interface according to your hardware.
  2. Select the serial or the parallel port where your devices are connected
  3. Press "APPLY"


Interface 2 � DDS/ADC connected to the LPT port

The Parallel Interface parameters that are selected when the �Default� button is pressed (see the file Sweep.in) are:

DDS Device=AD9851
DDS Multiplier=0
DDS Xtal freq=80000000
DDS Max freq=55000000
DDS Min freq=100000
DDS Offset=0
AD/C Device=8bit
AD/C Offset=0
AD/C Step=0,005
AD/C Channel=1

User can change any value, according the circuit design, accessing the window �DDS Generator�.

DDS supported are the Analog Device AD9850/AD9851 and AD9951.
If the AD9850 is used, no clock multiplier is required (Multiplier=0)
If AD9851 is selected and the internal 6xREFCLK multiplier should be engaged Multiplier=1 must be entered.
The Xtal frequency is entered in Hz, the program will calculate the frequency of the system clock based on the multiplier.
Example: device = AD9851, internal 6xREFCLK multiplier enabled (Multiplier=1), Xtal Frequency = 30000000, the system clock will be 180MHz

Max and Min frequency are the max and min values that can be selected for the START or STOP frequency, Analog Device recommend limiting the max value to the 40% of the system clock.

AD9850 DDS Generator

 

AD9951 DDS Generator

The frequency offset is entered from the menu "SetUp/Calibrate Generator"

Two AD/C chips are supported: the Texas Instruments TLC549 (8bits) and the TLC1549 (10 bits), those devices are pin to pin compatible.

AD/C Step is the value in milliVolt of the single step

Example:
step = 5mV for the 8bit TLC549 with Vref= 1.275 Volt

Step = 1.75 mV for the 10bit AD/C where the Vref = 1.8

Step is calculated as:

step = (Vmax � Vmin)/2^ (AD/C bits)

where Vmin is usually tied to the GND and Vmax = Vref

The AD/C offset is entered from the menu "SetUp/Calibrate Detector"

Interface 3 � MiniVNA connected to the USB port

The "Interface 3" allows program to send commands and receive back data from the serial USB port.

Please refer to the "Reference manual for mRS antenna analyser type miniVNA 0.1-180 MHz" for any detail, and for the virtual serial driver needed to access to the USB port:

Download from FTDI web site the latest VCP (Virtual Com Port) for your OS (WIN2000/XP or WIN98), the chip is FTDI232BM, look at their web site or the latest right now for windows 2000/XP.

Auxiliary commands

The frames AUX1 and AUX2 can be fully personalized from the menu "SetUp/Configuration".

Any frame can be disabled (NOT visible) checking the box "Enabled".

       
  1. This is the title shown when the frame is activated (menu "View/AUX1" or "View/AUX2")
  2. Button description, if this field is initialized "blank" the button will be disableb (NOT visible)
  3. Button value. This is the numeric value that will be added or subtracted from the frame value when the button is pressed or released

8 output lines are connected to the 8 buttons of each frame (see the Hardware Interface paragraph), driving 8 on/off channels.

The checkbox "Negative logic" allows user to select when a button is pressed the positive (1) or negative (0) output.

A slide bar is also available in the AUX2 frame.

User can personalize the MIN and MAX values.

If MIN = MAX the slide bar will be disabled (NOT visible)
MIN and MAX must be a numeric value.

This command can be used to interface any device that accepts the I2C protocol.

Any time the slide bar cursor is moved, the following command sequence, according with the specific of the device DS1803 Addressable Dual Digital Potentiomenter (Dallas Semiconductor � Maxim) bus is sent to the I2C:

Start
Write control byte = 80 (*)
Write command byte = 175 (*)
Write value = slide bar cursor position
Stop

(*) can be changed editing the [Aux2] section of the sweep.ini file