Preliminary Technical Data

EVAL-AD5933EB

Rev. PrC | Page 19 of 32

RealData = RealData - 65536

End If

ImagineryDataUpper = PortRead(&HD, &H96)

ImagineryDataLower = PortRead(&HD, &H97)

ImagineryData = ImagineryDataLower + (ImagineryDataUpper * 256)

'The imaginary 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 ImagineryData <= &H7FFF Then

' Positive Data.

Else

' Negative

'

ImagineryData = ImagineryData And &H7FFF

ImagineryData = ImagineryData - 65536

End If

‘-----------------Calculate the Impedance and Phase of the data at this frequency sweep point -----------

Magnitude = ((RealData ^ 2) + (ImagineryData ^ 2)) ^ 0.5

'the next section calculates the phase of the dft real and imaginary components

‘phase_sweep calculates the phase of the sweep data.

sweep_phase = (phase_sweep(ImagineryData, RealData) - calibration_phase_mid_point)

GainFactor = xx ‘this is determined at calibration.see gain factor section and Datasheet.

Impedance = 1 / (Magnitude * GainFactor)

' Write Data to each global array.

MagnitudeArray(IndexArray) = Impedance

PhaseArray(IndexArray) = sweep_phase

ImagineryDataArray(IndexArray) = ImagineryData

code(IndexArray) = Magnitude

RealDataArray(IndexArray) = RealData

Increment = Increment - 1 ' increment was set to number of increments of sweep at the start

FrequencyPoints(IndexArray) = Frequency

Frequency = Frequency + FrequencyIncrements ' holds the current value of the sweep freq

IndexArray = IndexArray + 1

------------- Check to see if sweep complete ----------------------

ReadbackStatusRegister = PortRead (&HD, &H8F)

ReadbackStatusRegister = ReadbackStatusRegister And &H4 ' mask off bit D2

'Increment to next frequency point Frequency

WritetToControlRegister &H80, &H30

Loop

‘--------------------- END OF SWEEP: Place device into POWERDOWN mode------------------------------------

'Enter Powerdown Mode,Set Bits D15,D13 in Control Register.

WritetToPart &H80, &HA0

END SUB

‘--------------------------------------------------------------------------------------------------------

‘The

programmed

sweep

is

now

complete

and

the

impedance

and

phase

data

is

available

to

read

in

the

two

‘arrays MagnitudeArray() = Impedance and PhaseArray() = phase.

sweepErrorMsg:

MsgBox "Error completing sweep check values"

End Sub

‘The

programmed

sweep

is

now

complete

and

the

impedance

and

phase

data

is

available

to

read

in

the

two

‘arrays MagnitudeArray() = Impedance and PhaseArray() = phase.