72 lines
2.5 KiB
Python
72 lines
2.5 KiB
Python
#!/usr/bin/python
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# Bicycle Bell/Horn firmware
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# Copyright (C) 2015 Stuart Longland
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#
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 2 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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import math
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import wave
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import struct
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import textwrap
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# Generate a bell sound
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F_sample = 6400 # 6.4kHz sample rate
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F_bell = 2063 # Fundamental frequency
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F_bell_mod = 15.625 # Modulated amplitude
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F_reverb = 3.77 # Reverberation frequency
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A_reverb = 0.07 # Reverberation amplitude
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duration = 1.0 # Duration
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decay = 1.0 # Decay
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samples = []
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bell = lambda t : ((1.0+math.cos(math.pi*t/duration))/2) * \
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(decay ** t) * \
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(1.0 - (A_reverb * math.cos(2*math.pi*F_reverb*t)) - (A_reverb/2)) * \
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(math.cos(2*math.pi*F_bell*t) * \
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math.sin(2*math.pi*F_bell_mod*t))
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for n in range(0, int(duration*F_sample)):
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t = float(n)/float(F_sample)
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samples.append(int(127*bell(t)) + 127)
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assert samples[-1] >= 0, '%s <= 0' % samples[-1]
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assert samples[-1] <= 255, '%s > 255' % samples[-1]
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num_samples = len(samples)
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# C output
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with file('bellsnd.c','w') as f:
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f.write('#include "bellsnd.h"\n')
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f.write('const uint8_t bell[%s] PROGMEM = {\n' % num_samples)
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f.write('\n'.join(textwrap.wrap(', '.join([str(s) for s in samples]),
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initial_indent='\t', subsequent_indent='\t',
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expand_tabs=False)))
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f.write('\n};\n')
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with file('bellsnd.h','w') as f:
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f.write('#include <stdint.h>\n')
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f.write('#include <avr/pgmspace.h>\n')
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f.write('#define BELL_RATE (%s)\n' % F_sample)
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f.write('#define BELL_SZ (%s)\n' % num_samples)
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f.write('const uint8_t bell[%s] PROGMEM;\n' % num_samples)
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# For the sake of analysis, we'll dump wav audio too
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f = wave.open('bellsnd.wav','w')
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f.setnchannels(1)
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f.setsampwidth(1)
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f.setframerate(F_sample)
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f.setnframes(num_samples)
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f.setcomptype('NONE','not compressed')
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f.writeframes(''.join([
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struct.pack('B', s) for s in samples
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]))
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f.close()
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