Chapter 3
Adjustment
3-30
ni.com
5.
Set the VCXO with the current “best-guess” value (NTSC mode) by
calling the function
ni54xx_CalibrateVCXO
. Set the following
parameters:
•
sessionHandle
—The handle of the calibration session for the
device
•
type
—
NI54XX_SET_VCXO_NTSC_M
6.
Measure the new frequency (
currentFrequency
).
7.
While the |frequency – 1 MHz| is greater than the tolerance
and
you
have not entered this loop more than 12 times, follow these steps:
a.
Call
ni54xx_CalAdjust
for measurement mode
NI54XX_SET_VCXO_NTSC_M
, which calculates the next
“best-guess” VCXO DAC value. The
measuredData
should be a
pointer to the measured frequency and the
actualData
should be
a pointer to the desired frequency (1 MHz). Call the function
ni54xx_CalAdjust
using the following parameters:
•
sessionHandle
—The handle of the calibration session for the
device
•
measurementMode
—
NI54XX_SET_VCXO_NTSC_M
•
actualData
—
&desiredFrequency
•
measuredData
—
¤tFrequency
b.
Set the VCXO with the new “best-guess” value (NTSC mode).
Call the function
ni54xx_CalibrateVCXO
and use the
following parameters:
•
sessionHandle
—The handle of the calibration session for the
device
•
type
—
NI54XX_SET_VCXO_NTSC_M
c.
Measure the new frequency (
currentFrequency
).
If you have exited the loop, the VCXO is adjusted within the tolerance or
as close as possible.
You have completed adjusting the NTSC Video Mode.