GLFSR Source

Galois LFSR pseudo-random source generating float outputs -1.0 - 1.0. Generates a maximal length sequence of length 2^degree-1.

Parameters

Degree

Degree of shift register must be in [1, 32]. If mask is 0, the degree determines a default mask (see digital_impl_glfsr.cc for the mapping).

Repeat

Set to repeat sequence.

Mask

Allows a user-defined bit mask for indexes of the shift register to feed back. For example the two fifth-order primitive polynomials, p(x) = x^5 + x^4 + x^3 + x^2 + 1 and p(x) = x^5 + x^2 + 1, will create m-sequences of length 2^n-1 where n is the degree. The mask is in byte format specifying the taps. The "one" in the polynomial does not correspond to a tap – it corresponds to the input to the first bit and is excluded from the mask. So the polynomials would be entered into the mask as 0x1E and 0x12 respectively. Note that these are integers, so after they are enter in the GNURadio block they will show as decimal 30 and 18, respectively.

Seed

Initial setting for values in shift register.

Example Flowgraph

Example of the two polynomials, p(x) = x^5 + x^4 + x^3 + x^2 + 1 and p(x) = x^5 + x^2 + 1, to create a Gold Code Sequence.

Source Files

C++ files

glfsr_source_b_impl.cc

glfsr.cc

Header files

glfsr_source_b_impl.h

Public header files

glfsr.h

Block definition

digital_glfsr_source_x.block.yml