On 2021-08-26 11:37 p.m., Jonathon Pendlum wrote:
Hi Jorn,
The offset frequency is implemented in the DDC block controller, see:
https://github.com/EttusResearch/uhd/blob/UHD-3.14.L/host/lib/rfnoc/ddc_block_ctrl_impl.cpp#L194
<https://github.com/EttusResearch/uhd/blob/UHD-3.14.L/host/lib/rfnoc/ddc_block_ctrl_impl.cpp#L194>.
Jonathon
To amplify on what Jonathon said above, the approach would be to use
set_rx_frequency to be desired-frequency+desired-offset (or
-desired-offset), then use
the DDC tuning to rotate the resulting baseband in the appropriate
direction and desired-offset magnitude to bring it to zero offset.
In multi-usrp without RFNOC, this is taken care of automatically, and
you generally don't have to worry about the math, which not only
involves the simple-case above,
but factoring-in things like minimum tuning step-size for the
hardware being used. Jonathon, do the RFNOC controllers "understand"
things like step size, or does
the user have to handle that themselves?
On Thu, Aug 26, 2021 at 2:06 AM Skorstad, Jørn <j...@nkom.no
<mailto:j...@nkom.no>> wrote:
Hello. I am using the UHD library 3.14.1 and C++ to control an
E310 radio. Without using RFNoC blocks it is possible to tune to
an offset frequency, using uhd::usrp::multi_usrp::set_rx_freq
(const tune_request_t &tune_request, size_t chan = 0). However,
when the software is using RFNoC blocks, it is only possible to
change RX center frequency:
uhd::rfnoc::rf_control::core_iface::set_rx_frequency(const double
/freq/, const size_t /chan/ ).
Is it possible to achieve the same offset tuning functionality
using RFNoC blocks? Have tried using set_rx_lo_freq(), but it
throws an exception, saying it is not supported on this model. I
have an RFNoC image with radio, DDC, window and FFT blocks on.
Jorn
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