PythonSupport

Python bindings for SoapySDR

The Python bindings for SoapySDR give the user access to the complete C++ API in Python. Because most of the API calls are identical to the C++ API, users should refer to the C++ headers and Doxygen for documentation. However, some calls have changed because of language differences. We will go over these calls in the examples below.

Dependencies

The Python bindings require SWIG and Python development files. We chose to use SWIG because it greatly simplified the developer effort required. To install the Python bindings, simply provide these dependencies before building SoapySDR.

To get the dependencies on a debian/ubuntu system:

sudo apt-get install python-dev swig

Example

import SoapySDR
from SoapySDR import * #SOAPY_SDR_* constants
import numpy #use numpy for buffers

#enumerate devices
results = SoapySDR.Device.enumerate()
for result in results: print(result)

#create device instance
args = dict(driver="rtl")
sdr = SoapySDR.Device(args)

#query device info
print(sdr.listAntennas(SOAPY_SDR_RX, 0))
print(sdr.listGains(SOAPY_SDR_RX, 0))
freqs = sdr.getFrequencyRange(SOAPY_SDR_RX, 0)
for freq in freqs: print(freq)

#apply settings
sdr.setSampleRate(SOAPY_SDR_RX, 0, 1e6)
sdr.setFrequency(SOAPY_SDR_RX, 0, 912.3e6)

#setup a stream (complex floats)
rxStream = sdr.setupStream(SOAPY_SDR_RX, "CF32")
sdr.activateStream(rxStream) #start streaming

#receive some samples
buff = numpy.array([0]*1024, numpy.complex64) #create a receive buffer
for i in range(10):
    sr = sdr.readStream(rxStream, [buff], len(buff))
    print sr.ret #num samples or error code
    print sr.flags #flags set by receive operation
    print sr.timeNs #timestamp for receive buffer

#shutdown a stream
sdr.deactivateStream(rxStream) #stop streaming
sdr.closeStream(rxStream)

API Differences

Factory: The Device::make() and Device::unmake() factory functions are not used in Python. Rather, the Device constructor directly calls into the make() factory, and the Device destructor directly calls into unmake() for cleanup. In addition, there are no associated thread-safety issues because the factory calls are protected by a Python mutex.

Streaming: The readStream() and writeStream() calls do not support C++'s return-by-reference. Therefore, any readback parameters are not passed into the associated calls. Rather, they are returned in the result object which contains the normal return code, output flags, and output timeNs.

• Rather than a pointer array, the readStream() and writeStream() calls expect a list of numpy arrays for receive and transmit buffers.