>
> Yes, the m-block stuff will provide a reasonable interface for doing
> this. Besides m-blocks, this also requires considerable work in the
> USRP FPGA to make it happen.
>
> The basic idea is that received packets will have time stamps in them
> that correspond to the arrival time that the first sample. Likewise,
> you'll be able to indicate that a particular packet should "hit
> the air" at a particular time.
>
> Eric
>
So, currently, among time stamping, isn't latency in configuring the blocks a
limitation? Perhaps the m-blocks will help with that, but I wasn't sure. And
I am assuming that you have to do some kind of hardware change (for a TDMA
case) while the flow graph is running (at the very least turning a transmitter
on / off, or changing the frequencies periodically). in some systems it might
be appropriate to "give up" some slots to reconfig, but is this what you had in
mind? Is the plan still to have m-blocks around in December? Currently, I have
been thinking about reconfiguration using the GNU Radio blocks as they are (e.g.
changing frequency, turning the transmitter on / off, etc.),and I found that the
latency was up to 1ms to turn the transmitter on using the 'set_enable' command
(meaning the latency between setting the enable
and moving on to other Python functions with GNU radio set to the highest
priority). Does this sound reasonable? Is is processor/OS dependent? The
code I used to test just turning the transmitter on and off is below. I am
also getting a warning with the destructor of the flex boards (The output of
the code is below) Could someone please help?
Thanks for your comment in advance,
David Scaperoth
from gnuradio import usrp, gr
import time
#print "directory", dir(usrp)
class benchmark_test(gr.flow_graph):
def __init__(self):
gr.flow_graph.__init__(self)
#USRP RX
self.decim = 128
self.rx_u = usrp.source_c()
adc_rate = self.rx_u.adc_rate()
self.rx_u.set_decim_rate(self.decim)
rx_subdev_spec = (0,0)
self.rx_subdevice = usrp.selected_subdev(self.rx_u,
rx_subdev_spec)
self.rx_subdevice.set_auto_tr(True)
print "Using RX d'board %s" %
(self.rx_subdevice.side_and_name(),)
self.rx_u.set_mux(usrp.determine_rx_mux_value(self.rx_u,
rx_subdev_spec))
self.rx_u.tune(self.rx_subdevice._which,
self.rx_subdevice,900e6)
self.null = gr.null_sink(gr.sizeof_gr_complex)
#USRP TX
self.tx_u = usrp.sink_c ()
dac_rate = self.tx_u.dac_rate();
tx_usb_rate = 500e3
usrp_interp = int(dac_rate // tx_usb_rate)
self.tx_u.set_interp_rate(usrp_interp)
tx_subdev_spec = (0,0)
self.tx_sd = usrp.selected_subdev(self.tx_u, tx_subdev_spec)
self.tx_sd.set_auto_tr(True)
print "Using TX d-board", self.tx_sd.name()
self.tx_u.set_mux(usrp.determine_tx_mux_value(self.tx_u,
tx_subdev_spec))
self.tx_u.tune(self.tx_sd._which, self.tx_sd,900e6)
self.tx_sd.set_enable(False)
#High Priority
r = gr.enable_realtime_scheduling()
if r != gr.RT_OK:
print "Warning: failed to enable realtime scheduling"
#Cosine
self.tx_sig = gr.sig_source_c(50e3, gr.GR_COS_WAVE, 6500, 1.0)
#Connect
self.connect(self.rx_u, self.null)
self.connect(self.tx_sig, self.tx_u)
def main():
fg = benchmark_test()
fg.start
time.sleep(0.5)
#raw_input("Press Enter To reset the Frequency")
start = time.time()
fg.tx_sd.set_enable(True)
stop = time.time()
time.sleep(0.5)
fg.tx_sd.set_enable(False)
print "It took", stop - start, "seconds to set transmit."
time.sleep(1.5)
#raw_input("Press Enter To reset the Frequency")
start = time.time()
fg.tx_sd.set_enable(True)
stop = time.time()
time.sleep(0.5)
fg.tx_sd.set_enable(False)
print "It took", stop - start, "seconds to set transmit."
time.sleep(1.5)
#raw_input("Press Enter To reset the Frequency")
start = time.time()
fg.tx_sd.set_enable(True)
stop = time.time()
time.sleep(0.5)
fg.tx_sd.set_enable(False)
print "It took", stop - start, "seconds to set transmit."
time.sleep(1.5)
#raw_input("Press Enter To reset the Frequency")
start = time.time()
fg.tx_sd.set_enable(True)
stop = time.time()
time.sleep(0.5)
fg.tx_sd.set_enable(False)
print "It took", stop - start, "seconds to set transmit."
raw_input("Press Enter to stop the flow graph.")
