On 9/5/20 2:59 PM, Ofer Saferman via USRP-users wrote:
> Hello,
>
> I am just starting out with the USRP E310 so bare with me.
> I am trying to capture samples to file using: ./rx_samples_to_file
> --freq 2.4e9 --rate 40e6 --bw 40e6 --gain 30 --nsamps 1000000 --file
> samp4.dat
> I get the following two warnings during processing:
> ------------------------------------------------------------------------------------------------------
> [WARNING] [RFNOC] [legacy_compat] No FIFO detected. Higher transmit
> rates may encounter errors.
> ------------------------------------------------------------------------------------------------------
>
> Setting RX Rate: 40.000000 Msps...
> [WARNING] [MULTI_USRP] The hardware does not support the requested RX
> sample rate:
> Target sample rate: 40.000000 MSps
> Actual sample rate: 16.000000 MSps
> ------------------------------------------------------------------------------------------------------
>
> Are the warnings related?
> I tried various combinations of number of samples bandwidths and sample
> rates and can't get more than 16 Msps.
> Why can't I get a sample rate of more than 16 MSps?
> Any help will be appreciated.
On top of what Marcus said, you need to specify master_clock_rate to set
other rates. 16 MHz is the default master clock rate. If you were able
to stream 40 MHz, you would need to do
./rx_samples_to_file --args master_clock_rate=40e6 [...other args..]
This is also relevant for other sampling rates. For example, 3 Msps is
something the device can handle (maybe even write to SD card), but you
would need a different master clock rate that is an integer multiple,
ideally an even one. In this case, I'd recommend master_clock_rate=12e6
which is 4 times 3. The USRP will engage 2 halfband filters to decimate
the rate. A master clock rate of 3 Msps is theoretically possible, but
not recommended since it will slow down other parts of the chip, too.
The FIFO warning is unrelated. You can ignore that. It should probably
not be there in the first place.
--M
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