W dniu 24.02.2018 o 23:10, Marcus D. Leech via USRP-users pisze:
> On 02/24/2018 04:27 PM, Piotr Krysik via USRP-users wrote:
>> Hi Marcus,
>>
>> Ad.A I doubted it as the time reported by both USRPs at the end of
>> synchronization function is about ~0.005 s. Anyway I increased the value
>> of start time to 9 seconds - with the same (negative) result.
>>
>> Ad.B When I get these B210s to time-synchronize I plan to implement
>> phase calibration method that doesn't rely on the capabilities provided
>> by B210's LO synthesizer. But I need to get to that point first. BTW
>> 180deg ambiguity is still better than what I expected.
>>
>> --
>> Best Regards,
>> Piotr Krysik
>>
> What if you use the time-stamps on the streams to time-align, and THEN
> cross-correlate?
>
> Remember that multi-usrp does this as a first step when it's dealing
> with multiple notionally-time-aligned streams from multiple devices.
>
> But that's only *WITHIN* a single multi-usrp object, and you
> necessarily have more than one multi_usrp object
To check this I connected two tag_debug blocks to usrp sources. They
caught following tags at offset 0 (first sample of the stream):
----------------------------------------------------------------------
Tag Debug:
Input Stream: 00
Offset: 0 Source: gr uhd usrp source2 Key: rx_time Value: {9
3.86875e-05}
Offset: 0 Source: gr uhd usrp source2 Key: rx_rate Value: 1e+06
Offset: 0 Source: gr uhd usrp source2 Key: rx_freq Value: 1e+09
----------------------------------------------------------------------
----------------------------------------------------------------------
Tag Debug:
Input Stream: 00
Offset: 0 Source: gr uhd usrp source1 Key: rx_time Value: {9
3.86875e-05}
Offset: 0 Source: gr uhd usrp source1 Key: rx_rate Value: 1e+06
Offset: 0 Source: gr uhd usrp source1 Key: rx_freq Value: 1e+09
----------------------------------------------------------------------
There are two rx_time tags with the same value. So they should be
aligned in time, but they aren't.
What is a bit unexpected for me is the non-zero fractional part.
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