Re: [Discuss-gnuradio] How to write data periodically in file sink

2017-05-21 12:24 GMT+03:00 Paul I. <address@hidden>:

You need to use USRP "issue_stream_cmd" method (mode: STREAM_MODE_NUM_SAMPS_AND_DONE). It's allow to receive burst of data by USRP timer.
If you work in GRC:
1) Disable streaming autostart for "UHD source"
2) Create your own block which will periodically issue stream commands (yes, you need to pass USRP pointer to it)
a) For stream command set "num_samples" = sample_rate * 1 sec
b) Read the USRP timer value, add some time offset to it and use this value as timestamp for the first stream command
c) Increment timestamp after every stream command
...
3) Profit!
2017-05-20 10:09 GMT+03:00 Gilad Beeri (ApolloShield) <address@hidden>:
If you need accuracy, I think the asynchronous nature of your method might problematic (will appreciate input from GR devs).
Maybe try a different approach - write the samples to a memory buffer, then read from the buffer the exact # of samples you want to write to a file.
On Fri, May 19, 2017 at 5:02 PM Deepak Gautam <address@hidden> wrote:
Dear luca,

I had already tried with controlling flow graph dynamically using start(), stop(), lock(), unlock() function. Here i have the part of code i had used.

tb=top_block_cls()
count=1
tb.start()
while (count<5):
time.sleep(1.0) #data is recorded in the file
tb.lock()
tb.disconnect((tb.uhd_usrp_source_0,0),(tb.blocks_file_sink_0, 0)) #disconnect source and block
tb.blocks_file_sink_0= blocks.file_sink(gr.sizeof_gr_complex*1, filename,False) # create new file sink to write
tb.connect((tb.uhd_usrp_source_0,0),(tb.blocks_file_sink_0, 0)) #connect source with new file
count=count+1
time.sleep(2.0) #wait
tb.unlock()
tb.stop()

This program should write the data for 1 second in the file, wait for 2 second and again write for 1 second to another file and so on for 5 4 times. I expect the total data written in the file to be same. But total number of samples recorded in the files are different. for my sampling rate of 25MSps, it should record 25MS per file, but it is around 22Mega sample with different number of data in different file. So it is difficult to reproduce the accurate signal from received data . My application requires very good phase coherence. So i am wondering whether there is something to do to solve in this method or i have to think of another idea.

Best Regards,
Deepak
On Mon, May 15, 2017 at 9:02 PM Moritz Luca Schmid <address@hidden> wrote:
Hey Deepak,

my first idea is to reconfigure the flowgraph. You could connect and disconnect your source for the time, you want to write data in your file sink and the time you don't want to.

You can find infos about the flowgraphs operations here.

Best

Luca

On 15.05.2017 13:53, Deepak Gautam wrote:

Currently i am working in the USRP using GNU Radio for my masters work. In my transmitter side, i send data continuously from file source followed by UHD Sink at the rate of 25 MSPS. In receiver side, I want to write the data in every two/three seconds after receiving from receiver USRP. Meaning, write data for 1 sec (25M samples), then dont write for next 2 second and again write for 1 sec and so on. Is there any suggestion for this purpose. I look forward for the resposne

Best Regards,

Deepak
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From:	Paul I.
Subject:	Re: [Discuss-gnuradio] How to write data periodically in file sink
Date:	Sun, 21 May 2017 13:32:11 +0300