Hi Martin,
the time tag 'tx_time' tells the USRP when to transmit - so far so
good. So I don't need any delay blocks because the USRP sink realizes
the delay, right? Assume i want to add a propagation delay of 240ms:
Setting 'tx_time' at the begin of the burst to 240ms will realize that?
Do I tag the burst in the code of the PDU-generator using
add_item_tag() or is there another block who does it after the
generator (I thought the pdu_to_tagged_stream - block tags the packet)?
The crucial code in the random_pdu_impl.cc is:
[...]
// pick a random vector length
int len = d_rvar();
len = std::max(d_length_modulo, len - len%d_length_modulo);
// fill it with random bytes
std::vector<unsigned char> vec(len);
for (int i=0; i<len; i++)
vec[i] = ((unsigned char) d_bvar()) & d_mask;
// send the vector
pmt::pmt_t vecpmt(pmt::make_blob(&vec[0], len));
pmt::pmt_t pdu(pmt::cons(pmt::PMT_NIL, vecpmt));
message_port_pub(PDU_PORT_ID, pdu);
[...]
My idea then is to use add_item_tag here with 'tx_time' as key for the
output vector "PDU_PORT_ID", i.d. "pdus" in GRC.
An additional question: How do I set a data rate that determines how
long a packet needs to be transmitted? Is that done by USRP as well?
By now the time sink just shows a blue, continuous signal as seen in
the attached picture.
Best regards,
Henning
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