[Discuss-gnuradio] how to decide the msgq_limit?

[Yan Nie]

Dear all,

I'm using gr.message_source as the signal source and using multiply_const_ff to 
set the amplitude of the signal then feeding the signal into USRP1 with LFTX 
plugged-in. The message need to be transmitted in my project is 3315 bytes. 
After the flow graph starting to run, msgq.insert_tail() is utilized to insert 
the message into the flow graph. The amplitude changes every time after the 
message is transmitted. I only called insert_tail() once in every cycle of 
transmission to feed the message and expect the message to be sent once, but 
the result turns out the times of the message transmission is ranging from once 
to 10 times, which means sometimes the message is only transmitted once, 
sometimes it continuously repeated 10 times. What's the problem would be? What 
decide the parameter, msgq_limit, which is the maximum number of message in the 
message queue? Can I send this 3315 bytes data as one message and set the 
msgq_limit as 1?

Really appreciate any of your suggestion!

Thanks,
Yan

The code related to message insert
try:
   while 1:
        tb.set_amplitude(2000)
        msg_13bit = gr.message_from_string(payload_13bit)
        tb._ls.msgq.insert_tail(msg_13bit)
        tb.set_amplitude(0)
        msg_stop = gr.message_from_string(payload_stop)
        tb._ls.msgq.insert_tail(msg_stop)