On 06/15/2020 06:45 PM, Aaron Smith wrote:
I am using a master clock rate of 48 MHz and a sample rate of 8 MHz.
When do you notice the timing inconsistency? For example, if you do a
number of timed transmits during the same session, are they
self-consistent? Where "session" is defined as "that stuff you do
after you've set the clock with 1PPS, etc".
On Mon, Jun 15, 2020, 4:41 PM Marcus D. Leech <patchvonbr...@gmail.com
<mailto:patchvonbr...@gmail.com>> wrote:
On 06/15/2020 03:42 PM, Aaron Smith wrote:
> I am using the python api.
>
> usrp = uhd.usrp.MultiUSRP()
>
> # Set gain, clock rate, sample rate etc...
>
> usrp.set_clock_source('external')
> usrp.set_time_source('external')
>
> ts_reset = uhd.types.TimeSpec(0.0)
> usrp.set_time_next_pps(ts_reset)
> time.sleep(1.0)
> last_pps = usrp.get_time_last_pps().to_ticks(1e9)
> if last_pps % int(1e9) != 0:
> print("Error failed to align clock")
>
> # The signal is complex float data, scaled to a max amplitude of
0.9
> approx 0.1 secs in duration
> signal_data = numpy.fromfile('signal.dat',dtype=numpy.complex64)
>
> wirefmt = 'sc16'
>
> sa = uhd.usrp.StramArgs('fc32',wirefmt)
> sa.channels = [0]
> stream = usrp.get_tx_stream(sa)
>
> # Send 3 seconds in future
> send_time = usrp.get_time_last_pps().get_real_secs() + 3.0
> metadata = uhd.type.TXMetadata()
> metadata.has_time_spec = True
> metadata.time_spec = uhd.types.TimeSpec(send_time)
>
> stream.send(signal_data, metadata)
>
> # Ensure the transmission is complete before returning
> time.sleep(4.0)
>
> sys.exit(0)
>
>
This probably has to do with uncertainty in the way the 1PPS
signal is
flopped into the device. What sample rate are you using, and what
master clock rate?
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