# I/O Modules
Modules for external communication, MIDI, OSC, and audio output.
## StereoOutput
The final audio output stage—every patch needs one.
```rust,ignore
let output = patch.add("output", StereoOutput::new());
patch.set_output(output.id());
```
### Inputs
| `left` | Audio | Left channel |
| `right` | Audio | Right channel |
### Normalled Behavior
If only `left` is connected, `right` automatically mirrors it.
```rust,ignore
// Mono output - left copied to right
patch.connect(mono_source, output.in_("left"))?;
// Stereo output
patch.connect(left_source, output.in_("left"))?;
patch.connect(right_source, output.in_("right"))?;
```
### Getting Output
```rust,ignore
let (left, right) = patch.tick(); // Returns (f64, f64)
```
---
## ExternalInput
Injects values from external sources (MIDI, UI, etc.).
```rust,ignore
use std::sync::Arc;
let cv = Arc::new(AtomicF64::new(0.0));
let input = patch.add("cv_in", ExternalInput::new(
Arc::clone(&cv),
SignalKind::CvUnipolar,
));
```
### Factory Methods
| `::voct(arc)` | V/Oct | Pitch from MIDI |
| `::gate(arc)` | Gate | Note on/off |
| `::trigger(arc)` | Trigger | Clock pulses |
| `::cv(arc)` | Unipolar CV | Mod wheel, expression |
| `::cv_bipolar(arc)` | Bipolar CV | Pitch bend |
### Thread-Safe Updates
```rust,ignore
// From MIDI thread
cv.set(midi_cc_value / 127.0 * 10.0);
// Audio thread reads latest value
let input_module = ExternalInput::cv(Arc::clone(&cv));
```
---
## MidiState
Comprehensive MIDI state tracking.
```rust,ignore
let midi = MidiState::new();
// In MIDI callback
midi.note_on(60, 100); // Note 60, velocity 100
midi.note_off(60);
midi.control_change(1, 64); // CC1 = 64
midi.pitch_bend(8192); // Center
// Read current state
let voct = midi.voct(); // V/Oct of current note
let gate = midi.gate(); // Gate state (0 or 5V)
let velocity = midi.velocity(); // 0.0 - 1.0
let mod_wheel = midi.cc(1); // CC value
```
---
## OSC Integration
### OscInput
Receives OSC messages as CV.
```rust,ignore
let osc_in = patch.add("cutoff_osc", OscInput::new("/synth/cutoff"));
patch.connect(osc_in.out("out"), vcf.in_("cutoff"))?;
```
### OscReceiver
Network OSC receiver.
```rust,ignore
let receiver = OscReceiver::new("127.0.0.1:9000")?;
// In your control thread
while let Some(msg) = receiver.recv()? {
match msg.address.as_str() {
"/synth/cutoff" => {
if let Some(OscValue::Float(v)) = msg.args.first() {
cutoff_cv.set(*v as f64 * 10.0);
}
}
_ => {}
}
}
```
### OscPattern
Pattern matching for OSC addresses.
```rust,ignore
let pattern = OscPattern::new("/synth/voice/*/cutoff");
// Matches:
// /synth/voice/1/cutoff
// /synth/voice/2/cutoff
// etc.
if pattern.matches(&msg.address) {
// Handle message
}
```
### OscBinding
Maps OSC to patch parameters.
```rust,ignore
let bindings = vec![
OscBinding::new("/synth/cutoff", "vcf.cutoff", 0.0..10.0),
OscBinding::new("/synth/resonance", "vcf.resonance", 0.0..1.0),
];
for binding in &bindings {
if let Some(value) = binding.process(&msg) {
patch.set_parameter(&binding.target, value);
}
}
```
---
## Web Audio
### WebAudioProcessor
Process audio for Web Audio API.
```rust,ignore
let config = WebAudioConfig {
sample_rate: 44100.0,
channels: 2,
buffer_size: 128,
};
let processor = WebAudioProcessor::new(patch);
```
### WebAudioWorklet
For AudioWorklet integration.
```rust,ignore
let worklet = WebAudioWorklet::new(patch);
// In worklet process()
worklet.process(&input, &mut output);
```
### Interleaving
Web Audio uses interleaved stereo:
```rust,ignore
// Convert from separate channels
let interleaved = interleave_stereo(&left, &right);
// Convert to separate channels
let (left, right) = deinterleave_stereo(&interleaved);
```
---
## Common Patterns
### MIDI-Controlled Synth
```rust,ignore
let pitch_cv = Arc::new(AtomicF64::new(0.0));
let gate_cv = Arc::new(AtomicF64::new(0.0));
let vel_cv = Arc::new(AtomicF64::new(5.0));
let pitch = patch.add("pitch", ExternalInput::voct(pitch_cv.clone()));
let gate = patch.add("gate", ExternalInput::gate(gate_cv.clone()));
let velocity = patch.add("vel", ExternalInput::cv(vel_cv.clone()));
// In MIDI handler
fn handle_note_on(note: u8, vel: u8) {
pitch_cv.set((note as f64 - 60.0) / 12.0);
vel_cv.set(vel as f64 / 127.0 * 10.0);
gate_cv.set(5.0);
}
fn handle_note_off(note: u8) {
gate_cv.set(0.0);
}
```
### OSC-Controlled Parameters
```rust,ignore
let bindings = HashMap::from([
("/filter/cutoff", vcf_cutoff_cv.clone()),
("/filter/reso", vcf_reso_cv.clone()),
("/env/attack", env_attack_cv.clone()),
]);
// In OSC handler
if let Some(cv) = bindings.get(&msg.address.as_str()) {
if let Some(OscValue::Float(v)) = msg.args.first() {
cv.set(*v as f64);
}
}
```