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https://github.com/tinygo-org/drivers.git
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Ayke van Laethem
148 lines
1.6 KiB
Go
148 lines
1.6 KiB
Go
package tone
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// Note represents a MIDI note number. For example, Note(69) is A4 or 440Hz.
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type Note uint8
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// Define all the notes in a format similar to the Tone library in the Arduino
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// IDE.
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const (
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A0 Note = iota + 21 // 27.5Hz
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AS0
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B0
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C1
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CS1
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D1
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DS1
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E1
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F1
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FS1
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G1
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GS1
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A1 // 55Hz
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AS1
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B1
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C2
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CS2
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D2
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DS2
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E2
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F2
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FS2
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G2
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GS2
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A2 // 110Hz
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AS2
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B2
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C3
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CS3
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D3
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DS3
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E3
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F3
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FS3
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G3
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GS3
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A3 // 220Hz
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AS3
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B3
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C4
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CS4
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D4
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DS4
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E4
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F4
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FS4
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G4
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GS4
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A4 // 440Hz
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AS4
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B4
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C5
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CS5
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D5
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DS5
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E5
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F5
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FS5
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G5
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GS5
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A5 // 880Hz
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AS5
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B5
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C6
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CS6
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D6
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DS6
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E6
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F6
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FS6
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G6
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GS6
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A6 // 1760Hz
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AS6
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B6
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C7
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CS7
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D7
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DS7
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E7
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F7
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FS7
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G7
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GS7
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A7 // 3520Hz
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AS7
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B7
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C8
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CS8
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D8
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DS8
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E8
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F8
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FS8
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G8
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GS8
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A8 // 7040Hz
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AS8
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B8
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)
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// Period returns the period in nanoseconds of a single wave.
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func (n Note) Period() uint64 {
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if n == 0 {
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// Assume that a zero note means no sound.
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return 0
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}
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octave := (n - 9) / 12
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note := (n - 9) - octave*12
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// Start with a base period (in nanoseconds) of 6.875Hz (quarter the
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// frequency of A0) and shift it right with the octave to get the base
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// period of this note.
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// 145454545 = 1e9 / 6.875
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basePeriod := uint32(145454545) >> octave
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// Make the pitch higher based on the note within the octave.
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period := uint64(basePeriod) * uint64(tones[note]) / 32768
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return period
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}
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// Constants to calculate the pitch within an octave. Python oneliner:
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// [round(1e9/(440*(2**(n/12))) / (1e9/440) * 0x8000) for n in range(12)]
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var tones = [12]uint16{
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32768,
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30929,
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29193,
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27554,
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26008,
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24548,
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23170,
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21870,
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20643,
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19484,
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18390,
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17358,
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}
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