[Discuss-gnuradio] A couple of questions related to UHD

[Feng Andrew Ge]

I posted one question in an early email, but it might be better to put 
it together with other questions here. I'd greatly appreciate your answers.

(1)  When transmitting UHD packets (with USRP2 + WBX), after each 
transmission, there is either one or a few "U" printed out. What does 
"U" mean?  Is it used in the update packet from USRP2 to the host?

(2) In uhd:usrp:single_usrp, there is a function "read_rssi", is this 
function enabled? If so, does it mean that we can read RSSI value 
directly from USRP2? I suppose that this function is implemented on the 
FPGA since there exits a rssi.v function in the uhd library.

(3) In uhd:usrp:single_usrp, it seems that "get_rx_rate" is for setting 
sampling rate, but then what is "get_rx_bandwidth" for?

(4) In flow control,  how to specify "ups_per_fifo", just like 
device_address["ups_per_fifo"] = "xx"? Also, what are the FIFOs on USRP2 
and what are their default sizes?

(5) For "concurrency_hint", it says "the number of threads to run the IO 
service", does it mean the total number of threads associated with the 
UDP socket for each USRP_SINK or USRP_SOURCE, or something else?

(6) Do control messages generated by functions like get/set_tx_gain and 
get/set_tx-freq have to wait on the same UDP buffers which are also used 
for exchanging data samples between GNU Radio and USRP?

Andrew