Preliminary Technical Data

EVAL-AD5933EB

Rev. PrC | Page 17 of 32

phase2 = (theta * 180) / pi

'convert from radians to degrees

ElseIf ((real > 0) And (img < 0)) Then

theta = Atn(img / real)

'4th quadrant theta = minus angle

phase2 = ((theta * 180) / pi ) +360

ElseIf ((real < 0) And (img < 0)) Then

theta = -pi + Atn(img / real)

'3rd quadrant theta img/real is positive

phase2 = (theta * 180) / pi

ElseIf ((real < 0) And (img > 0)) Then

theta = pi + Atn(img / real)

'2nd quadrant img/real is neg

phase2 = (theta * 180) / pi

End If

End Function

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

Private Sub Sweep ()

’ the main sweep routine

‘This routine coordinates a frequency sweep using a mid point gain factor (see datasheet).

'The gain factor at the mid-point is determined from the real and imaginary contents returned at this mid

‘point frequency and the calibration impedance.

'The bits of the status register are polled to determine when valid data is available and when the sweep is

‘complete.

'-----------------------------------------------------------------------------------------------------------

IndexArray = 0

'initialize counter variable.

Increment = NumberIncrements + 1 'number of increments in the sweep.

Frequency = StartFrequency

'the sweep starts from here.

‘------------------------- PROGRAM 30K Hz to the START FREQUENCY register ---------------------------------

DDSRefClockFrequency = 16E6

‘Assuming a 16M Hz clock connected to MCLK

StartFrequency = 30E3

‘frequency sweep starts at 30K Hz

TempStartFrequency = (StartFrequency / (DDSRefClockFrequency / 4)) * 2^27 ‘dial up code for the DDS

TempStartFrequency = Int(TempStartFrequency)

‘30K Hz = 0F5C28 hex

StartFrequencybyte0 = 40

‘40 DECIMAL = 28 HEX

StartFrequencybyte1 = 92

‘92 DECIMAL = 5C HEX

StartFrequencybyte2 = 15

’15 DECIMAL = 0F HEX

'Write in data to Start frequency register

WritetToPart &H84, StartFrequencybyte0

'84 hex lsb

WritetToPart &H83, StartFrequencybyte1

'83 hex

WritetToPart &H82, StartFrequencybyte2

'82 hex

‘--------------------------------- PROGRAM the NUMBER OF INCREMENTS register ------------------------------

‘The sweep is going to have 150 points 150 DECIMAL = 96 hex

'Write in data to Number Increments register

WritetToPart &H89, 96

‘lsb

WritetToPart &H88, 00

‘msb

‘--------------------------------- PROGRAM the FREQUENCY INCREMENT register ------------------------------

‘The sweep is going to have a frequency increment of 10Hz between successive points in the sweep

DDSRefClockFrequency = 16E6

‘Assuming a 16M Hz clock connected to MCLK

FrequencyIncrements = 10

‘frequency increment of 10Hz

TempStartFrequency = (FrequencyIncrements / (DDSRefClockFrequency / 4)) * 2^27 ‘dial up code for the DDS

TempStartFrequency = Int(TempStartFrequency)

’10 Hz =

335 decimal = 00014F hex

FrequencyIncrementbyt0 = 4F

‘335 decimal = 14f hex

FrequencyIncrementbyt1 = 01

FrequencyIncrementbyt2 = 00

'Write in data to frequency increment register

WritetToPart &H87, FrequencyIncrementbyt0

'87 hex lsb

WritetToPart &H86, FrequencyIncrementbyt1

'86 hex

WritetToPart &H85, FrequencyIncrementbyt2

'85 hex msb

‘--------------------------------- PROGRAM the SETTLING TIME CYCLES register ------------------------------