Re: [Discuss-gnuradio] Change the RX frequency of USRP Source using a tag

[Marcus Müller]

Hi Damindra,


On 18.03.2017 20:31, Damindra Bandara wrote:
> Hi,
>
> I was able to add a tag (tx_freq) and change the the frequency of USRP
> sink  successfully. I want to do the same thing for USRP source. Since
> source doesn't take any input I was wondering how to do this.
It does! It has a message port, which accept commands. You can enable
the display of that port in the Block options, if you're designing with GRC.
>
> I tried with message strobe and it worked, but I need to change the
> frequency based on some external event. When that event happens I want
> to add a tag to trigger the frequency change.
ah, you already found that :)
Tags are things that are attached to a sample flow – the source of a
sample stream can add a tag, but you can't add tags and make the source
react to that – that'd be inversion of causality.

so, I think what you should do is write some class that sends a message
as soon as the event happens.

Best regards,
Marcus