So basically i tried assigning the sync words only in the first call to work() and the result was that only the first packet was transmitted successfully, so either gnuradio scheduler is erasing all the output buffer before the call to the work function, or the output buffer is a new allocation and has nothing to do with the output buffer of the previous call to work.
In any case, is there a way i can make that gnuradio just allocs that buffer once and does not change the values of it, so i can be sure that in successive calls to work the buffer retains the values written by previous calls to work, if none of the consumer blocks changes their input buffer?
Thanks in advantage.