On 25/03/2023 15:45, George Edwards wrote:
> Hello GNURadio Community,
>
> I am about to use a N310 radio to transmit and receive data. My
> problem is I do not know how to interpret the sample rate parameter. I
> will pose some questions that I am seeking answer to (I read there are
> 3 Master Clocks for the N310):
>
> Q1. The transmitter Sample Rate setting: is this the sample rate of
> the data that will enter the N310 hardware from the GRC software
> component?
yes.
>
> Q2. The receiver Sample Rate setting: is this the sample rate that the
> N310 hardware outputs the connected GRC software component?
Yes
>
> Q3. Now I was reading the interpolation/decimation in the N310 radio
> and there were statements made about the device having 3 Master
> Clocks. Let's assume I choose the Master Clock frequency of 125e6 for
> the transmitter and I wish to upsample by a factor of 100 in the N310
> transmitter. I take it that this assumes that GRC component connected
> to the N310 USRP Tx block must be running at a sample rate 1.25e6 and
> that by setting the Sample Rate in the USRP block to 1.25e6 (with the
> Master Clock set to 125e6) then N310 hardware will upsample the data
> entering to 125e6, right?
Yes.
>
> Q4. Now, for the converse at the receiver: with the USRP Master Clock
> set to 125e6 and USRP Sample Rate set to 1.25e6, then the USRP block
> will deliver a sample rate of 1.25e6 to the attached GRC component,
> right?
Yes,
>
> Q5. What happens if I do not select one of the Master Clocks, but
> provide the Sample Rates at the respective USRP Tx/Rx?
The default master-clock if you don't specify in a device argument is by
default (as I recall) 125MHz. But that can be
easily verified by asking for some sample-rate that is a proper
fraction of 125MHz, and seeing if UHD changes it to
something different.