Re: [Discuss-gnuradio] UHD USRP Sink Stream Tagging

[King Qiu]

Hi Josh,
I have done the same work as Alex. I modified the code in
gr_message_source. I added a tx_sob tag and a tx_time tag to the first
byte of the message, and a tx_eob tag to the last byte of the message.
Assuming:
1. there are 100 bytes in a message(or we call it a packet)
2. bpsk modulation is employed
3. set samples_per_symbol to 2
So there are 800 symbols or 1600 samples in the packet. 
In the output of the gr_message_source block, the 0 byte is tagged with
the tx_sob and the tx_time, and the 99 byte is tagged with the tx_eob. 

Then in the output of the symbol map block, the 0 symbol is tagged with
the tx_sob and the tx_time, and the 792 symbol is tagged with the
tx_eob. 

After pulse shaping filter, the 0 sample is tagged with the tx_sob and
the tx_time, and the 1584 sample is tagged with the tx_eob.

My questions are as follow:
1. The 1599 sample is the last sample in the packet, but the tx_eob tag
are added to the 1584 sample. So, what will happen to the 1585-1599
samples in the usrp? Are they transmitted by the usrp immediately after
the 1584 sample? 

2. Is it necessary to adding the tx_eob tag exactly to the last (1599)
sample? How can I do this?

Best regards,
King Qiu