audio_generate_dac_lut.py

 1#!/usr/bin/env python3
 2#
 3# Copyright 2020 JohSchneider
 4#
 5# This program is free software: you can redistribute it and/or modify
 6# it under the terms of the GNU General Public License as published by
 7# the Free Software Foundation, either version 2 of the License, or
 8# (at your option) any later version.
 9#
10# This program is distributed in the hope that it will be useful,
11# but WITHOUT ANY WARRANTY; without even the implied warranty of
12# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13# GNU General Public License for more details.
14#
15# You should have received a copy of the GNU General Public License
16# along with this program.  If not, see <http://www.gnu.org/licenses/>.
17#
18
19AUDIO_DAC_BUFFER_SIZE=256
20AUDIO_DAC_SAMPLE_MAX=4095
21
22def plot(values):
23    for v in values:
24        print('0'* int(v * 80/AUDIO_DAC_SAMPLE_MAX))
25
26def to_lut(values):
27    for v in values:
28        print(hex(int(v)), end=", ")
29
30
31from math import sin, tau, pi
32
33samples=[]
34
35def sampleSine():
36    for s in range(AUDIO_DAC_BUFFER_SIZE):
37        samples.append((sin((s/AUDIO_DAC_BUFFER_SIZE)*tau - pi/2) + 1 )/2* AUDIO_DAC_SAMPLE_MAX)
38
39def sampleTriangle():
40    for s in range(AUDIO_DAC_BUFFER_SIZE):
41        if s < AUDIO_DAC_BUFFER_SIZE/2:
42            samples.append(s/(AUDIO_DAC_BUFFER_SIZE/2) * AUDIO_DAC_SAMPLE_MAX)
43        else:
44            samples.append(AUDIO_DAC_SAMPLE_MAX - (s-AUDIO_DAC_BUFFER_SIZE/2)/(AUDIO_DAC_BUFFER_SIZE/2) * AUDIO_DAC_SAMPLE_MAX)
45
46#compromise between square and triangle wave,
47def sampleTrapezoidal():
48    for i in range(AUDIO_DAC_BUFFER_SIZE):
49        a=3 #slope/inclination
50        if (i < AUDIO_DAC_BUFFER_SIZE/2):
51            s = a * (i * AUDIO_DAC_SAMPLE_MAX/(AUDIO_DAC_BUFFER_SIZE/2)) + (1-a)*AUDIO_DAC_SAMPLE_MAX/2
52        else:
53            i = i - AUDIO_DAC_BUFFER_SIZE/2
54            s = AUDIO_DAC_SAMPLE_MAX - a * (i * AUDIO_DAC_SAMPLE_MAX/(AUDIO_DAC_BUFFER_SIZE/2)) - (1-a)*AUDIO_DAC_SAMPLE_MAX/2
55
56        if s < 0:
57            s=0
58        if s> AUDIO_DAC_SAMPLE_MAX:
59            s=AUDIO_DAC_SAMPLE_MAX
60        samples.append(s)
61
62
63#sampleSine()
64sampleTrapezoidal()
65#print(samples)
66plot(samples)
67to_lut(samples)