SimpleLFO v0.1

gistfile1.txt

class SimpleLFO:
    LIBRARY = {"triangle": {"waveform": (0, 32767, 0, -32767),
                            "interpolate": True, "nowrap": False, "once": False},
               "square": {"waveform": (32767, -32767), 
                          "interpolate": False, "nowrap": False, "once": False},
               "sine": {"waveform": tuple([round(32767.0 * math.sin(2 * math.pi * idx / 100)) for idx in range(100)]),
                        "interpolate": True, "nowrap": False, "once": False},
               "sawtooth": {"waveform": tuple([round(32767 - 2 * 32767 * idx / (20 - 1)) for idx in range(20)]),
                        "interpolate": True, "nowrap": False, "once": False},

               ### Oneshots
               "uniramp": {"waveform": (32767, 0),
                           "interpolate": True, "nowrap": True, "once": True},
               "reverseramp": {"waveform": (-32767, 32767),
                               "interpolate": True, "nowrap": True, "once": True}
              }

    def __init__(self, 
                 waveform="triangle",
                 rate=1.0,
                 scale=1,
                 offset=0,
                 once=None,
                 interpolate=True,
                 nowrap=None):

        self.rate = rate
        self.scale = scale
        self.offset = offset  
        if isinstance(waveform, str):
            self._waveform = self.LIBRARY[waveform]["waveform"]
            self._interpolate = self.LIBRARY[waveform]["interpolate"]
            self._nowrap = self.LIBRARY[waveform]["nowrap"] if nowrap is None else nowrap
            self._once = self.LIBRARY[waveform]["once"] if once is None else once
        else:
            self._waveform = waveform
            self._interpolate = interpolate
            self._nowrap = True if (once and nowrap is None) else bool(nowrap)
            self._once = bool(once)

        self._mean = sum(self._waveform) / len(self._waveform)
        self._waveform_len = len(self._waveform)
        self._period_ns = 1e9 / rate
        ### TODO work out the real condition for this!!
        self._idx_ghz = rate * (self._waveform_len - 1 if self._nowrap else self._waveform_len) * 1e-9 
        self._rescale = scale / 32768.0
        self._starttime_ns = time.monotonic_ns()
        self._endfirst_ns = self._starttime_ns + self._period_ns
        self._update_tick = 1


    def retrigger(self):
        self._starttime_ns = time.monotonic_ns()

    @property
    def value(self):
        now_ns = time.monotonic_ns()
        frac_idx, int_idx = math.modf((now_ns - self._starttime_ns) * self._idx_ghz)
        idx = int(int_idx) % self._waveform_len  ### int() required here for index use
        interpolate = self._interpolate
        w_value = None
        if self._once:
            if self._nowrap:
                last_cycle_idx = self._waveform_len - 1
                new_idx = last_cycle_idx
            else:
                last_cycle_idx = self._waveform_len
                new_idx = 0

            ### Check to see if once waveform has finished
            if int_idx >= last_cycle_idx:
                if self._nowrap:
                    idx = new_idx
                    interpolate = False
                else:
                    w_value = self._mean

        if w_value is None:
            if interpolate:
                next_idx = idx + 1
                if next_idx >= self._waveform_len:
                    next_idx = 0

                w_value = (1.0 - frac_idx) * self._waveform[idx] + frac_idx * self._waveform[next_idx]
            else:
                w_value = self._waveform[idx]

        return w_value * self._rescale + self.offset