On 12/19/2018 02:29 PM, Devin Kelly wrote:
I'm using 500 kHz sampling rate. Wouldn't a lower rate effect my ToF
accuracy? My understanding is that with 500 kHz sample rate my best
ToF accuracy would be 2 us. My next question is why is the ToF
shifting by less than 2 us (1/500e3)? My master clock is 16MHz so
maybe the ToF shifts by multiples of 1/16e9?
Devin
For a 500ksps sample rate, I wouldn't expect there to be any overruns,
unless your flow-graph is quite complicated.
Sample streams carry timestamps, so you can look at the timestamps when
an overrun occurs and compute how many samples were
lost.
On Wed, Dec 19, 2018 at 2:01 PM Marcus D. Leech via USRP-users
<[email protected] <mailto:[email protected]>> wrote:
On 12/19/2018 01:56 PM, Devin Kelly via USRP-users wrote:
> Hello,
>
> I have an X310 transmitting packets to an E310, the E310 can
> successfully demodulate the packet and estimate the time of flight.
> I'm sending one packet per second for about half an hour and the
ToF
> estimate is very consistent, except for when I have an overflow
on the
> E310. I get an overflow once every 15-20 minutes or so.
>
> When I get an overflow my ToF estimate increases permanently by a
> small amount, enough to affect my application. For example, I
might
> get 500 packets in a row with a ToF of 100 us each, then I get an
> overflow and all my remaining packets have a ToF of 101.6 us.
All the
> USRPs are wired together so my channel isn't changing. I tried to
> figure out if I could compensate for the difference but I couldn't
> figure it out. I also tried to reset the PPS on the E310, which
> didn't work.
>
> I know it's on the receive side because I have multiple
receivers and
> I can match each overflow to each ToF change. On the E310 I'm using
> UHD 3.9.2. Can anyone help me figure this out?
>
> Also, is there a newer image I should be using for the E310? Or, a
> newer UHD? It doesn't look like the E310 is supported much
anymore,
> or is there something I'm not seeing?
>
> Thanks,
> Devin
>
What sample rate are you using on the E310? Can you operate with a
lower rate?
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