blob: 20ef4528e669ca48f15b6badf70d4aa84dfc82bf (
plain) (
blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
|
#!/usr/bin/octave -qf
% SPDX-FileCopyrightText: 2023 Brian Woods
% SPDX-License-Identifier: GPL-2.0-or-later
% simple octave executable script to generate freq graph from filter output
% impulse_file;
%graph_file
freq = NaN;
width = NaN;
signednesses = {"unsigned", "signed"};
signedness = NaN;
function print_help()
printf("%s <impulse_file> <sample_freq> <width> <signedess> <graph_file>\n", ...
program_name());
printf("where:\n");
printf("\tinput_file: input filename of output of filter\n");
printf("\tsample_freq: freqency in sample length\n");
printf("\twidth: bit width of the output\n");
printf("\tsignedness: it is either: signed, unsigned\n");
printf("\tgraph_file: output graph filename\n");
endfunction
% input parsing
arg_list = argv ();
if (nargin != 5)
printf("Too few or too many arguements given.\n");
print_help()
quit;
endif
freq = abs(real(str2double(arg_list{2})));
if isnan(freq)
printf("Can't parse <freq>.\n");
print_help()
exit;
endif
width = abs(floor(real(str2double(arg_list{3}))));
if isnan(width)
printf("Can't parse <width>.\n");
print_help()
exit;
endif
for i = 1:length(signednesses)
if strcmp(arg_list{4},signednesses{i})
signedness = i;
break
endif
endfor
if isnan(signedness)
printf("can't parse <signedness>.\n");
print_help()
exit;
endif
impulse_file = arg_list{1};
graph_file = arg_list{5};
% end input parsing
% calc ranges
if signedness == 1
range_max = 2**width - 1;
range_min = 0;
else
range_max = 2**(width-1) -1;
%makes things easier not to use the extra negative number
range_min = -range_max;
endif
% read in input
impulse_data = dlmread(impulse_file);
if (exist("impulse_data", "var") != 1)
printf("Can't read input data file\n");
exit;
endif
impulse_data = impulse_data/range_max;
% referenced from matlab site
impulse_len = length(impulse_data);
impulse_fft = fft(impulse_data);
freq_full = abs(impulse_fft/impulse_len);
freq_half = freq_full(1:(impulse_len/2)+1);
freq_half(2:end-1) = 2*freq_half(2:end-1);
fig = figure('visible','off');
freq_list = freq*(0:(impulse_len/2))/impulse_len;
plot(freq_list,freq_half);
title("frequency responce of filter output");
xlabel("frequency (Hz)");
ylabel("amplitude x(k)");
print(graph_file);
|
