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Re: [Discuss-gnuradio] Continous Transmission using GNU RADIO. Is it rea

From: CEL
Subject: Re: [Discuss-gnuradio] Continous Transmission using GNU RADIO. Is it really possible?
Date: Mon, 13 May 2019 12:22:59 +0000

Dear Mehtap,

On Mon, 2019-05-13 at 15:03 +0300, mehtap özkan wrote:
> Dear All,
>  I have implemented a CPFSK transmitter succesfully using GNU RADIO.


> The blocks are PRBS Source->Scrambler (G3RUH)-> CPFSK Mod-> UHD Sink. The 
> reference HW receiver receives and demodulates the signal quite well.

It's always a nice feeling when something works with real hardware :)

> Then I remove the PRBS Source and place a UDP Source+UART block as the data 
> source.
> When the connected client sends continous data, everything is fine (except at 
> the start of transmission where the receiver needs time to lock to the 
> incoming signal).
> When I send some bytes from the client and stop sending, the transmission 
> becomes burst-like and the receiver can demodulate pretty much nothing.
> I found the culprit which is the Scrambler, when there is no input to the 
> Scrambler, there is no output, so there is no RF output.

Well, I wouldn't call it a "culprit", since it does what it's designed
to do: Scramble data. 

>  I have also developed a FPGA Continous CPFSK transmitter in the past and the 
> scrambler there was producing output every clock cycle as there was 0 in its 
> Input, so that guaranteed continous output.
>  The real problem is: What should I do to force some Input bits to the 
> Scrambler, even there is no real data?

The gr-eventstream module might be of interest to you!

Best regards,

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