You
can put a block in sequence with the samples that does two
things in the work() function:
1)
copy
the input buffer to the output buffer using memcpy or
something similar since it doesn’t look like you need to
process the samples at all
2)
keep
track of “number of samples remaining before re-tune” in a
local variable that you set to NSAMPS_PER_TUNE, and
decrement it by noutput items as you described. If this
variable gets down to 1 (or 0?) re-set it to NSAMPS_PER_TUNE
and call the set_command_time() function to retune. You’ll
have to follow the lead of the burst tagging example to know
precisely what absolute time you need to retune, and you
also have to make sure the re-tune command gets called with
some lead-time, so I’m not quite sure how to handle this.
This
is just a rough guess of how to do it; I’m sure there are
other nuances. With this approach you shouldn’t need to
worry about how many samples were passed to your work()
function since you always decrement your count variable by
how many you received.
Hope
that helps!
Sean
From:
address@hidden
[mailto:address@hidden]
On Behalf Of Daniel Labarowski
Sent: Friday, June 29, 2012 4:21 PM
To: address@hidden
Subject: [BULK] [Discuss-gnuradio] How many samples
per call to work function?
Importance: Low
Hello,
I am going to be making a C++ block which will either change
the value of a variable (which would be passed to it by a
pointer) or call the tune function of a USRP sink (passed by a
pointer) after a certain number of samples have been passed to
the block. This is related to my question here.
In order to do this, I need to establish how often the
work function is called. From my past experience writing
GNURadio signal processing blocks, it looks like around 8190
samples are passed to the blocks work function each time it is
called, but this tends to vary wildly. Also, I haven't tested
whether this is dependent on data format of the input/output.
My current plan to build the block is to increment a (local,
not the on being passed) variable by noutput items each time
the work function is called. Once a certain number of samples
have been handled by the block, I will change the frequency. I
was wondering if it is even possible to construct a block with
no output or input, and if it is possible whether the work
function would ever get called and whether its noutputitems
(or ninputitems) would correspond to the number of samples
flowing through the rest of the flowgraph? If it cant be done
this way, I suppose it would be no real issue to give the
block an input so that it can count ninputitems then just not
do anything with the input items. Just trying to get a feel
for the best way to do this and to find out, in general, how
frequently the work function of the block is called and how
many samples are passed with each call? Thanks!
-Dan