Source code for sk_dsp_comm.coeff2header
"""
Digital Filter Coefficient Conversion to C Header Files
Copyright (c) March 2017, Mark Wickert
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
1. Redistributions of source code must retain the above copyright notice, this
list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice,
this list of conditions and the following disclaimer in the documentation
and/or other materials provided with the distribution.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
The views and conclusions contained in the software and documentation are those
of the authors and should not be interpreted as representing official policies,
either expressed or implied, of the FreeBSD Project.
"""
import numpy as np
import scipy.signal as signal
import matplotlib.pyplot as plt
from matplotlib import pylab
from numpy import int16, rint, loadtxt
import os
from logging import getLogger
log = getLogger(__name__)
[docs]
def fir_header(fname_out, h):
"""
Write FIR Filter Header Files
Mark Wickert February 2015
"""
M = len(h)
N = 3 # Coefficients per line
f = open(fname_out, 'wt')
f.write('//define a FIR coefficient Array\n\n')
f.write('#include <stdint.h>\n\n')
f.write('#ifndef M_FIR\n')
f.write('#define M_FIR %d\n' % M)
f.write('#endif\n')
f.write('/************************************************************************/\n');
f.write('/* FIR Filter Coefficients */\n');
f.write('float32_t h_FIR[M_FIR] = {')
kk = 0;
for k in range(M):
# k_mod = k % M
if (kk < N - 1) and (k < M - 1):
f.write('%15.12f,' % h[k])
kk += 1
elif (kk == N - 1) & (k < M - 1):
f.write('%15.12f,\n' % h[k])
if k < M:
f.write(' ')
kk = 0
else:
f.write('%15.12f' % h[k])
f.write('};\n')
f.write('/************************************************************************/\n')
f.close()
[docs]
def fir_fix_header(fname_out, h):
"""
Write FIR Fixed-Point Filter Header Files
Mark Wickert February 2015
"""
M = len(h)
hq = int16(rint(h * 2 ** 15))
N = 8 # Coefficients per line
f = open(fname_out, 'wt')
f.write('//define a FIR coefficient Array\n\n')
f.write('#include <stdint.h>\n\n')
f.write('#ifndef M_FIR\n')
f.write('#define M_FIR %d\n' % M)
f.write('#endif\n')
f.write('/************************************************************************/\n');
f.write('/* FIR Filter Coefficients */\n');
f.write('int16_t h_FIR[M_FIR] = {')
kk = 0;
for k in range(M):
# k_mod = k % M
if (kk < N - 1) and (k < M - 1):
f.write('%5d,' % hq[k])
kk += 1
elif (kk == N - 1) & (k < M - 1):
f.write('%5d,\n' % hq[k])
if k < M:
f.write(' ')
kk = 0
else:
f.write('%5d' % hq[k])
f.write('};\n')
f.write('/************************************************************************/\n')
f.close()
[docs]
def iir_sos_header(fname_out, SOS_mat):
"""
Write IIR SOS Header Files
File format is compatible with CMSIS-DSP IIR
Directform II Filter Functions
Mark Wickert March 2015-October 2016
"""
Ns, Mcol = SOS_mat.shape
f = open(fname_out, 'wt')
f.write('//define a IIR SOS CMSIS-DSP coefficient array\n\n')
f.write('#include <stdint.h>\n\n')
f.write('#ifndef STAGES\n')
f.write('#define STAGES %d\n' % Ns)
f.write('#endif\n')
f.write('/*********************************************************/\n');
f.write('/* IIR SOS Filter Coefficients */\n');
f.write('float32_t ba_coeff[%d] = { //b0,b1,b2,a1,a2,... by stage\n' % (5 * Ns))
for k in range(Ns):
if (k < Ns - 1):
f.write(' %+-13e, %+-13e, %+-13e,\n' % \
(SOS_mat[k, 0], SOS_mat[k, 1], SOS_mat[k, 2]))
f.write(' %+-13e, %+-13e,\n' % \
(-SOS_mat[k, 4], -SOS_mat[k, 5]))
else:
f.write(' %+-13e, %+-13e, %+-13e,\n' % \
(SOS_mat[k, 0], SOS_mat[k, 1], SOS_mat[k, 2]))
f.write(' %+-13e, %+-13e\n' % \
(-SOS_mat[k, 4], -SOS_mat[k, 5]))
# for k in range(Ns):
# if (k < Ns-1):
# f.write(' %15.12f, %15.12f, %15.12f,\n' % \
# (SOS_mat[k,0],SOS_mat[k,1],SOS_mat[k,2]))
# f.write(' %15.12f, %15.12f,\n' % \
# (-SOS_mat[k,4],-SOS_mat[k,5]))
# else:
# f.write(' %15.12f, %15.12f, %15.12f,\n' % \
# (SOS_mat[k,0],SOS_mat[k,1],SOS_mat[k,2]))
# f.write(' %15.12f, %15.12f\n' % \
# (-SOS_mat[k,4],-SOS_mat[k,5]))
f.write('};\n')
f.write('/*********************************************************/\n')
f.close()
[docs]
def freqz_resp_list(b, a=np.array([1]), mode='dB', fs=1.0, n_pts=1024, fsize=(6, 4)):
"""
A method for displaying digital filter frequency response magnitude,
phase, and group delay. A plot is produced using matplotlib
freq_resp(self,mode = 'dB',Npts = 1024)
A method for displaying the filter frequency response magnitude,
phase, and group delay. A plot is produced using matplotlib
freqz_resp(b,a=[1],mode = 'dB',Npts = 1024,fsize=(6,4))
Parameters
----------
b : ndarray of numerator coefficients
a : ndarray of denominator coefficents
mode : display mode: 'dB' magnitude, 'phase' in radians, or
'groupdelay_s' in samples and 'groupdelay_t' in sec,
all versus frequency in Hz
n_pts : number of points to plot; default is 1024
fsize : figure size; defult is (6,4) inches
Mark Wickert, January 2015
"""
if type(b) == list:
# We have a list of filters
N_filt = len(b)
else:
return None
f = np.arange(0, n_pts) / (2.0 * n_pts)
for n in range(N_filt):
w, H = signal.freqz(b[n], a[n], 2 * np.pi * f)
if n == 0:
plt.figure(figsize=fsize)
if mode.lower() == 'db':
plt.plot(f * fs, 20 * np.log10(np.abs(H)))
if n == N_filt - 1:
plt.xlabel('Frequency (Hz)')
plt.ylabel('Gain (dB)')
plt.title('Frequency Response - Magnitude')
elif mode.lower() == 'phase':
plt.plot(f * fs, np.angle(H))
if n == N_filt - 1:
plt.xlabel('Frequency (Hz)')
plt.ylabel('Phase (rad)')
plt.title('Frequency Response - Phase')
elif (mode.lower() == 'groupdelay_s') or (mode.lower() == 'groupdelay_t'):
"""
Notes
-----
Since this calculation involves finding the derivative of the
phase response, care must be taken at phase wrapping points
and when the phase jumps by +/-pi, which occurs when the
amplitude response changes sign. Since the amplitude response
is zero when the sign changes, the jumps do not alter the group
delay results.
"""
theta = np.unwrap(np.angle(H))
# Since theta for an FIR filter is likely to have many pi phase
# jumps too, we unwrap a second time 2*theta and divide by 2
theta2 = np.unwrap(2 * theta) / 2.
theta_dif = np.diff(theta2)
f_diff = np.diff(f)
Tg = -np.diff(theta2) / np.diff(w)
# For gain almost zero set groupdelay = 0
idx = pylab.find(20 * np.log10(H[:-1]) < -400)
Tg[idx] = np.zeros(len(idx))
max_Tg = np.max(Tg)
# print(max_Tg)
if mode.lower() == 'groupdelay_t':
max_Tg /= fs
plt.plot(f[:-1] * fs, Tg / fs)
plt.ylim([0, 1.2 * max_Tg])
else:
plt.plot(f[:-1] * fs, Tg)
plt.ylim([0, 1.2 * max_Tg])
if n == N_filt - 1:
plt.xlabel('Frequency (Hz)')
if mode.lower() == 'groupdelay_t':
plt.ylabel('Group Delay (s)')
else:
plt.ylabel('Group Delay (samples)')
plt.title('Frequency Response - Group Delay')
else:
s1 = 'Error, mode must be "dB", "phase, '
s2 = '"groupdelay_s", or "groupdelay_t"'
log.info(s1 + s2)
[docs]
def ca_code_header(fname_out, Nca):
"""
Write 1023 bit CA (Gold) Code Header Files
Mark Wickert February 2015
"""
dir_path = os.path.dirname(os.path.realpath(__file__))
ca = loadtxt(dir_path + '/ca1thru37.txt', dtype=int16, usecols=(Nca - 1,), unpack=True)
M = 1023 # code period
N = 23 # code bits per line
Sca = 'ca' + str(Nca)
f = open(fname_out, 'wt')
f.write('//define a CA code\n\n')
f.write('#include <stdint.h>\n\n')
f.write('#ifndef N_CA\n')
f.write('#define N_CA %d\n' % M)
f.write('#endif\n')
f.write('/*******************************************************************/\n');
f.write('/* 1023 Bit CA Gold Code %2d */\n' \
% Nca);
f.write('int8_t ca%d[N_CA] = {' % Nca)
kk = 0;
for k in range(M):
# k_mod = k % M
if (kk < N - 1) and (k < M - 1):
f.write('%d,' % ca[k])
kk += 1
elif (kk == N - 1) & (k < M - 1):
f.write('%d,\n' % ca[k])
if k < M:
if Nca < 10:
f.write(' ' * 20)
else:
f.write(' ' * 21)
kk = 0
else:
f.write('%d' % ca[k])
f.write('};\n')
f.write('/*******************************************************************/\n')
f.close()
