Hi all,
I've been working on a flowgraph that controls sweeping a USRP by retuning and
then dumping samples until catching the sample tagged with rx_freq of the
correct value.
I was confused as to why I was still getting mountains of garbage samples
(several hundred thousand at 10MS/s) after catching the rx_freq tag, until
today I put "assert(usrp->get_sensor("lo_locked").to_bool())" after the block
that identifies the correct rx_freq tag, and it popped immediately.
I'm wondering about the prudence of saying a sample is "at a certain frequency"
before the LO has had a chance to settle.
I also realize that gr-uhd folks are trying to make the message interface more
robust, and the rx_freq tag is an awesome idea, but what I really want to know
is what is the first USABLE sample at my requested freq. If I still have to
carry around a usrp_source pointer so that I can check the LO state, then the
tags output by the usrp_source lose a lot of appeal.
Any chance of making rx_freq tag "the first usable sample", or is there a good
reason for the way it works that I haven't considered?
-Doug
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