dynamic sequencer support

ch32v-insert-coin/src/synthesizer.rs

@@ -11,6 +11,8 @@ const SQUARE_WAVETABLE: [u8; 2] = [0, 100];
 
 pub struct SynthesizerService {
     pub synth: SimpleWavetableSynthesizer<SimpleWavetable<'static, u8>>,
+    pub enabled: bool,
+    pub need_service: bool,
 }
 
 impl SynthesizerService {
@@ -18,19 +20,29 @@ impl SynthesizerService {
         let square_wt = SimpleWavetable::new(&SQUARE_WAVETABLE);
         let synth = SimpleWavetableSynthesizer::new(square_wt, clock_freq_hz);
 
-        Self { synth }
+        Self {
+            synth,
+            enabled: true,
+            need_service: false,
+        }
     }
 
     pub fn tick(&mut self) {
-        self.synth.tick();
+        if self.enabled {
+            self.synth.tick();
+        }
     }
 
     pub fn need_service(&self) -> bool {
-        self.synth.has_new_output()
+        self.need_service || self.synth.has_new_output()
     }
 
-    pub fn service(&mut self) -> u8 {
-        self.synth.get_output()
+    pub fn service(&mut self) -> Option<u8> {
+        if self.enabled {
+            Some(self.synth.get_output())
+        } else {
+            None
+        }
     }
 }
 
@@ -40,10 +52,14 @@ impl SynthesizerService {
     }
 
     pub fn enable(&mut self) {
+        self.enabled = true;
+        self.need_service = true;
         // TODO: write the enable function
     }
 
     pub fn disable(&mut self) {
+        self.enabled = false;
+        self.need_service = true;
         // TODO: write the disable function
     }
 }