Re: [Discuss-gnuradio] Problems passing the control between blocks - message passing

[Jose Torres Diaz]

Hi John, 

I wrote the code in C++ based on UHD_AMsg_source.cc, provided in GRExtras. In my work function, I've finished it using return -1 (ie. the block has finished processing correctly) as shown below:

int work(
        const InputItems &,
        const OutputItems &
    ){
      //work definition here (ie. generate a packet and post downstream)
      return -1; //done running, work done status
    }

However, in that way the block in GNU Radio Companion runs only once. The other possibility is not to use "return" at all, but in that case what I have is:

1. BLOCK 1 generates a packet
2. BLOCK 1 post the packet downstream

Step 1 and 2 repeats "N times". When finishes, it gives the control to BLOCK 2 to process the message. However, I need a sequence as follows:

1. BLOCK 1 generates a packet
2. BLOCK 1 post the packet downstream
3. BLOCK 2 process the packet
4. BLOCK 2 post the message again downstream and so on...

Step 1 to 4 should repeat "N times".

Thanks again for your help, 

Jose

On Wed, Oct 17, 2012 at 4:52 PM, John Malsbury <address@hidden> wrote:

Jose,

Try a while(1) with a block and  a blocking call to pop msg's off the queue:

self.pop_msg_queue()

Should help you avoid the return -1

Or maybe I've misunderstood your problem...?

-John

On Tue, Oct 16, 2012 at 11:18 PM, Jose Torres Diaz <address@hidden> wrote:

Hi All,

I'm working with 2 blocks that I've created using "UHD_AMsg_Source" as a reference model. In these blocks, I am passing pmt_dict type as messages, ie:

 this->post_msg(0, AMSG_KEY, dictionary,_id);

Where, dictionary contains data/metadata that I can read in the next block downstream.

BLOCK 1  -- (pmt_dict included in the message) -->  BLOCK 2

The blocks are working ok, but the problem is that when I want to generate several packets and post them downstream, BLOCK 1 runs until finishes and then BLOCK 2 takes the control until finishes. The problem is the "return" sentence in my work function. I did 2 possible ways

Option 1: Using -1

work {
//work here
return -1
}
 
In this way BLOCK 1 stops working after one iteration and it does not run as many times as I want.

Option 1: Not using return

work {
//work here
}

In this way BLOCK 1 runs many times and posts messages downstream all those times, but it gives the control to BLOCK 2 when it finishes. Then, BLOCK 2 takes the messages from the message queue. However, this implementation is not useful for me. BLOCK 1 should post a message downstream and then, BLOCK 2 takes the message and work with the packet.

Any suggestion is welcome, thanks a lot for your time,

Regards,

Jose

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