fpfind

An add-on implementation of frequency compensation for qcrypto.

Requirements:

• Python 3.8 and above, running in Linux
• gcc, if running freqcd (preferably in PATH for auto-compilation)

Install the library (alternatively, clone and install locally with pip install -e.):

pip3 install git+https://github.com/s-fifteen-instruments/fpfind.git

Binaries and scripts will be exposed to the path; commonly used scripts are listed below.

fpfind -t {TIMESTAMPS1} -T {TIMESTAMPS2}
freqcd -X -udF fpipe -f 568 < {TIMESTAMPS}
[costream -V5 ... |] freqservo -V5 -udF fpipe -f 568
parse_timestamps -A1 -X -p {TIMESTAMPS}

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Limitations

• The FFT buffer size is limited to 2**31 bins due to the implicit casting to int32 performed internally by np.bincount on older versions of numpy. This corresponds to a buffer order value upper bounded to q = 31 for fpfind. To bypass this limitation, supply an alternative implementation for np.bincount.

Troubleshooting

Certain issues may appear when attempting an install on RaspbianOS:

• Importing numpy yields the error message stating libopenblas.so could not be found (this is the underlying linear algebra library for Numpy); installing the libopenblas-dev library fixes this, e.g. apt install libopenblas-dev