Re: [Discuss-gnuradio] getting the fpga counter for timestamping

[Josh Blum]

On 05/07/2013 04:59 PM, NaceurElOuni wrote:
> Thank you josh,
> 
> I just want to be sure, are stream tags handled by timing of the FPGA (clock
> ticks) or the timestamps are being inserted from within the host userspace, 
> because am getting too much variability on the latency when timestamps are
> inserted in the OS.
> 

For transmit: The host generates the timestamps and the samples and
sends this to the FPGA. The FPGA interprets the timestamps and waits
until the exact moment specified by the time to transmit.

The timestamps specify an absolute time on the device, so there isnt
room for variability, the packet with time either arrives before the
scheduled transmission time or its late and wont be transmitted.

This is the case for all the USRP devices except USRP1.

-josh

> regards.
> 
> 
> 
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