Vaisala RVP900

Appendix D _________________________________________________ RVP900 Developer's Notes
VAISALA______________________________________________________________________ 417
difference is that the default trigger generation is superceded by the
custom iNominalTrigSequence_stag method.
- iNominalTrigSequence_stag—This is a direct clone of the factory
default trigger code in rvp8main/open/txsubs.c, except that the PRT
sequence is altered by a zero-mean pseudo-random set of time
staggers.
To compile and run this mode, modify rvp8main/site/mt_user.c as
described in Section D.5.3 Example: Real-Time Interrupt Histogram on
page 408. In addition, import the default FFT behavior for the compute
processes by changing rvp8proc/site/ct_user.c to:
void ctInitMajorMode_user1( void ) { ctInitMajorMode_fft() ; }
Build and install all of these changes by compiling both the rvp8main and
rvp8proc trees. You may then request this user mode from ascope and
verify the micro-staggered PRTs on a delayed sweep oscilloscope. For
example, at 1 KHz PRF and with a delayed sweep of 1 ms, you should see
a flurry of "second bang" triggers whose leading edges jitter over a 5 s
span. Contrast this with the normal FFT mode, which has constant
interpulse spacing.
Another way to verify the staggered PRTs is to check the live timeseries
data using the example source utility that is included in the rdasubs
directory:
$ /usr/sigmet/src/rda/rdasubs/rvp8ts_example –headers
The PRF was set to a low value of 100 Hz in order to limit the rate at which
the live headers were printed. A 72 MHz IFD was used in this
measurement, hence the nominal time to the previous and next 100 Hz
pulses would be 720000 clock ticks. However, because of the
micro-stagger, the actual interpulse PRTs are seen to vary.
-SeqNum- --AZ-- --EL-- PrevPRT NextPRT Bank Wave TX
00014289 0.00 0.00 720088 720120 0 60 00
0001428A 0.00 0.00 720120 720080 0 61 00
0001428B 0.00 0.00 720080 720056 0 62 00
0001428C 0.00 0.00 720056 719952 0 63 00
0001428D 0.00 0.00 719952 719992 0 0 00
0001428E 0.00 0.00 719992 719832 0 1 00
0001428F 0.00 0.00 719832 720040 0 2 00