This is the GNU Radio UHD package. It is the interface to the UHD library to connect to and send and receive data between the Ettus Research, LLC product line. To use the UHD blocks, the Python namespaces is in gnuradio.uhd, which would be normally imported as:
The relevant blocks are listed in the UHD Interface group.
A quick listing of the details can be found in Python after importing by using:
Ettus Research maintains the comprehensive documentation to the underlying UHD driver, which can be found at:
The UHD Doxygen page is located at:
The UHD sink and source can be controlled by a message port. These message ports take commands, which are PMTs formatted as such:
(command, value, [channel])
A command PMT is either a pair or a tuple. If it's a tuple, it must have either 2 or 3 elements. Any other type of PMT will throw an error.
command part is a string, which defines the command.
value is a PMT whose format depends on the command issued. Finally,
channel is an integer PMT value that specifies which channel this command shall be specified on. If this value is omitted, then it either applies this command to all channels or channel zero, depending on which command is used.
This PMT would set the frequency to 1.1 GHz on all channels. We make use of the pmt::mp() function which automatically sets the PMT types. Assume we only want to set the frequency on channel 1 (i.e. the second channel). In this case, we must construct a tuple:
The following commands are understood by both UHD Source and Sink:
|Command name||Value Type||Description|
|double||Sets the Tx or Rx frequency. Defaults to all channels.|
|double||Sets an LO offset. Defaults to all channels.|
|double||Sets the Tx or Rx gain (in dB). Defaults to all channels.|
A typical option parser setup for a UHD device looks like
To use these options to create a UHD source object:
Frequently, your application may need a sample rate that is not supported by the UHD device. If you have extra CPU power to spare, you can easily set the sample rate you want, then ask the device what the actual sample rate set was. Then, you can easily create an arbitrary resampler to take care of the difference.