On Thu, Jun 5, 2014 at 4:19 PM, David Halls <[email protected]> wrote:
> -------- Original message -------- > From: Activecat > Date:2014/06/05 7:57 AM (GMT+00:00) > To: David Halls ,[email protected] > Subject: Re: [Discuss-gnuradio] Scheduling a block even with no input > items RE: Flow graph blocking when doing 2x1 transmission > > David, > Basically my idea to solve the problem may involve an overhaul of your > existing flowgraph, as below: > > 1). You must understand that the output of UHD source is at constant > rate. In particular I am referring to the "Relay Rx" USRP. > Even when the USRP does not receive any RF signal, it keeps > sending out zeros (plus noise) as its output, at constant rate. > > Try to make all your blocks behave in this way. I am referring to > the blocks between the "Relay Rx" and "Relay Tx". > The idea is: keep transmitting, don't produce no output at any > time. If nothing need to be produced, then output zeros at constant rate. > In this case all your custom blocks are either sync block, > decimation or interpolation blocks. You don't need any general block. > > 2). With above condition fulfilled, we could ensure that the data fed > into the "Relay Tx" USRP is at constant rate, and we could then determine > this rate by simple calculations. > The data stream into the "Relay Tx" USRP will not stop at any > instance. It is 'consistent'. > > 3). You want the "Relay Rx" USRP ignores the received signal during the > time that the "Relay Tx" USRP is transmitting, that is fine. > But just try to make the downstream block of "Relay Rx" USRP keep > transmitting zeros rather than stop transmitting during this period. > > 4). With these, you will have both "Relay Tx" USRP and "Source" USRP > transmitting at constant data rate and nonstop. > They could be transmitting at different rates, that is ok, and > this is not difficult to handle. > > With this, you avoid the initial problem (problem of occasionally there > is no items at one of the inputs) mentioned in this thread, which is the > root cause of your problem. > Then your problem is solved ! > > Great! Thanks active cat. This will take some time, I'll will report back once I have it working!! :) Hi David, I have a "frequency counter" block [1], could be used as an example. The "freq_counter1" is a general block, it was implemented as a sync block in "freq_counter2". You may run examples/flowgraph_07.grc and flowgraph_08.grc to see their outputs. 1. https://github.com/activecat/gr-test2
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