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Sending a packet once but receiving multiple times at receiver side (GNURadio, Zynq702+FMComms5)

Hello there,

The problem I am facing is may be not solely depends on FMCOMMS5 but also on my grc flowgrpah in GNURadio. I am asking though.

I am sending a '.txt' file once with 100 sequence of 0,1s by using OFDM simulation grc examples in GNURadio and also using a pair of zynq702+FMCOMMS5 set as transceiver. The software simulation transmitted it only once. But when I am transmitting it with FMCOMMS5, it recieves muliple times at the reciever side. That means the '.txt' file continue to receive more than 100 sequence untill I stop simulation with transceiver. 

If anybody can give me some explaination or suggestion for modification of Board configuration or Flowgraph would be grateful. Please use below pictures for my reference model.

Note: I havent done any modification for transmission on both board just connected HDMI plug once for signal visualization in the oscilloscope. 

Thank you.


Parents Reply
  • If you set "Cyclic" to false, do you receive one sequence as expected? Do you still see a part of the expected sequence missing if you connect one zynq702+FMCOMMS5 in RF loopback i.e., connect the transmit and receive ports? Does your simulation work as expected when you remove all hardware, create a single flowgraph by just connecting the OFDM transmitter block to Throttle and the rest of the receiver blocks, and run it? Do you get the expected sequence without loss?


  • Hi, thanks for your reply. By setting Cyclic to False, I get only one time transmission which was I looking for. But I want to add that I get everytime around 10-12 sequences (0,1s) out of 100 and its not similar with transmitted file. I am considering this missmatch as there is no channel coding in my flowgraph. But I am concerned about receiving too little amount of inputs .

    And the answer for simulation in single flowgraph is Yes. I get 100 sequences out 100 in software simulation (w/o hardware connection). 

    Do I need to add any addtional blocks after/before FMCOMM blocks?

    BR, Rupak 

  • Since you were using a pair of zynq702+FMCOMMS5, and I see two different IPs indicating a pair of zynq702+FMCOMMS5, I'm guessing you manually run two separate flowgraphs for Tx and Rx, one after the other? Is that correct? 

    You could perhaps zero-pad your waveform at the output of OFDM Tx, with the length of zero-padding sequence set sufficiently long to see if you are able to match the waveform before trying to match the transmitted file. No other blocks should be needed after/before FMCOMMS blocks.