public APU(ARM7TDMI cpu, Scheduler.Scheduler scheduler)
{
this.Channels = new Channel[] { sq1, sq2, wave, noise };
this.FIFO[0] = this.FIFOA = new FIFOChannel(cpu, 0x0400_00a0);
this.FIFO[1] = this.FIFOB = new FIFOChannel(cpu, 0x0400_00a4);
// initial APU events
scheduler.Push(new Event(FrameSequencerPeriod, this.TickFrameSequencer));
foreach (Channel ch in this.Channels)
{
scheduler.Push(new Event(ch.Period, ch.Tick));
}
scheduler.Push(new Event(SamplePeriod, this.ProvideSample));
}
private void TickFrameSequencer(Event sender, Scheduler.Scheduler scheduler)
{
this.FrameSequencer++;
switch (this.FrameSequencer & 7)
{
case 0:
case 4:
foreach (Channel ch in this.Channels)
{
ch.TickLengthCounter();
}
break;
case 2:
case 6:
foreach (Channel ch in this.Channels)
{
ch.TickLengthCounter();
}
this.sq1.DoSweep();
break;
case 7:
this.sq1.DoEnvelope();
this.sq2.DoEnvelope();
this.noise.DoEnvelope();
break;
}
sender.Time += FrameSequencerPeriod;
scheduler.Push(sender);
}
public void Tick(Event sender, Scheduler.Scheduler scheduler)
{
this.OnTick();
if (!this.SoundOn())
{
this.CurrentSample = 0;
}
else
{
this.CurrentSample = this.GetSample();
}
sender.Time += this.Period;
scheduler.Push(sender);
}
private void ProvideSample(Event sender, Scheduler.Scheduler scheduler)
{
int SampleLeft = 0, SampleRight = 0;
for (int i = 0; i < 4; i++)
{
if (!ExternalChannelEnable[i])
{
continue;
}
if (this.MasterEnableRight[i])
{
SampleRight += this.Channels[i].CurrentSample;
}
if (this.MasterEnableLeft[i])
{
SampleLeft += this.Channels[i].CurrentSample;
}
}
// SOUNDCNT_L volume control does not affect FIFO channels
SampleRight = (int)((SampleRight * this.MasterVolumeRight) / 8);
SampleLeft = (int)((SampleLeft * this.MasterVolumeLeft) / 8);
switch (this.Sound1_4Volume)
{
case 0:
// 25%
SampleLeft >>= 2;
SampleRight >>= 2;
break;
case 1:
// 50%
SampleLeft >>= 1;
SampleRight >>= 1;
break;
default:
// 100% / prohibited
break;
}
/*
* GBATek:
* Each of the two FIFOs can span the FULL output range (+/-200h).
* Each of the four PSGs can span one QUARTER of the output range (+/-80h).
* So we multiply the output of the FIFO by 4
*/
for (int i = 0; i < 2; i++)
{
if (!ExternalFIFOEnable[i])
{
continue;
}
if (this.DMAEnableRight[i])
{
SampleRight += this.FIFO[i].CurrentSample << (this.DMASoundVolume[i] ? 1 : 2); // false = 50%, true = 100%
}
if (this.DMAEnableLeft[i])
{
SampleLeft += this.FIFO[i].CurrentSample << (this.DMASoundVolume[i] ? 1 : 2); // false = 50%, true = 100%
}
}
SampleRight = (int)(SampleRight * Amplitude);
SampleLeft = (int)(SampleLeft * Amplitude);
if (this.ExternalEnable)
{
SpinWait.SpinUntil(() => this.speaker.NeedMoreSamples); // prevent buffer overflow
this.speaker.AddSample((short)SampleLeft, (short)SampleRight);
}
sender.Time += SamplePeriod;
scheduler.Push(sender);
}