#!/usr/bin/env python3
# Directly create your own sounds using a bit of math!
# This code uses frequency modulation,
# so volume cannot be changed, and there is only one frequency at a time.
# For the passive buzzer, earbuds, or as line out.
# Use a 220 ohm resistor in series with passive buzzer or earbuds.
# Use something like a 100,000 ohm resistor for line out to reduce voltage below 2 V.

# Select the type of sound by choosing which
# of the "t = " lines is uncommented the main while loop.
# Except for the 400 Hz constant tone,
# all of my sounds use the complete 80 Hz to 2000 Hz range.

# (c) 2018 Bradley Knockel




pin = 21

# how long is each pulse in seconds?
# good values: 0.2, 1, 2
period=1;




from math import *

import RPi.GPIO as IO
IO.setmode(IO.BCM)
IO.setup(pin, IO.OUT)

import time
start = time.time()
timee = (time.time()-start)*1000000.0  # timee is microseconds since start


try:
  while 1:
    val = (time.time()%period)/(1.0*period)  # from 0 to 1
    # now calculate t, half the period of the sound wave in microseconds

    # sin^2(t) -> t
    #t = 250.0 + 6000.0*pow(sin(pi*val),2.0)

    # sin(t) -> t
    #t = 250.0 + 6000.0*(sin(2.0*pi*val)+1.0)/2.0

    # sin(e^t) -> t
    # works well with longer period
    #t = 250.0 + 6000.0*(sin(2.0*pi*exp(val)*20.0)+1.0)/2.0

    # decimalPart(t) -> t
    #t = 250.0 + 6000.0*val

    # decimalPart(t) -> f
    t = 1000000.0/(160.0 + 3840.0*val)

    # decimalPart(-t) -> t
    #t = 250.0 + 6000.0*(1.0-val)

    # decimalPart(-t) -> f
    #t = 1000000.0/(160.0 + 3840.0*(1.0-val))

    # e^(decimalPart(t)) -> t
    # e^(-decimalPart(t)) -> f
    #t = exp(log(250.0)+log(25.0)*val)

    # e^(-decimalPart(t)) -> t
    # e^(decimalPart(t)) -> f
    #t = exp(log(250.0)+log(25.0)*(1-val))

    # e^(sin(t)) -> t
    #t = exp(log(250.0)+log(25.0)*(sin(2.0*pi*val)+1.0)/2.0)

    # 400 Hz tone
    #t = 1000000/(2*400)
  
    while (time.time()-start)*1000000.0 < timee:
      pass
    IO.output(pin, 1)
    timee += t
    while (time.time()-start)*1000000.0 < timee:
      pass
    IO.output(pin, 0)
    timee += t




except:
  pass

IO.cleanup()