PRBS code in Python

prbs Python

# TremaineConsultingGroup
# Brian Tremaine
# prbs.py
# August 11, 2021
# Prototype PRBS generator
#

#   PRBS15 = x^15 + x^14 + 1   Wikipeda

#           .--->X-------------------------------------------------------->
#           |    |                                                         |
#   bit     |    |                                                         |
#   <-----  D    D    D   D   D   D   D   D   D   D   D   D   D   D   D <--
#
#           bit15          <-------------------------------           bit1
#
#   PRBS7 = x^7 + x^6 + 1
#
#            .--->X------------------------>
#            |    |                         |
#   bit      |    |                         |
#   <------  D    D    D   D   D   D   D <--|
#
#            bit7   <---------------   bit1

from scipy import signal
import matplotlib.pyplot as plt

""" ============ main ======================================
"""
if __name__ == '__main__':   
    
     bit= list()
     start = 1;
     lfsr = start;
     i= 1
     while True:
         fb= ((lfsr>>14) ^ (lfsr>>13) & 1)
         lfsr = ((lfsr<<1) + fb) & (2**15-1) 
         bit.append(fb)
         print (i, lfsr, fb, bin(lfsr) )
         if lfsr==start :
             print('repeat pattern length', i)
             break;
         i = i+1
    
     bit = [float(i) for i in bit]
     
     for i in range(2**15-1):
         bit[i]= 2*(bit[i] - 0.5)
     
     plt.plot(bit); plt.title('PRBS')
     plt.show()
     
     u = signal.correlate(bit,bit)
     plt.plot(u); plt.title('PRBS corr')
     plt.show()
     
     print("done!")