Persist pitch bend between notes for FM channels

Matches behaviour of PSG. FM special mode will be fixed in another commit

src/midi_fm.c

@@ -18,6 +18,7 @@ struct MidiFmChannel {
     u8 velocity;
     u8 pan;
     bool percussive;
+    u16 pitchBend;
 };
 
 static MidiFmChannel fmChannels[MAX_FM_CHANS];
@@ -26,6 +27,7 @@ static u8 pitchIsOutOfRange(u8 pitch);
 static u8 effectiveVolume(MidiFmChannel* channelState);
 static void updatePan(u8 chan);
 void midi_fm_reset(void);
+u16 effectiveFreq(MidiFmChannel* fmChan);
 
 static const FmChannel** presets;
 static const PercussionPreset** percussionPresets;
@@ -46,6 +48,7 @@ void midi_fm_reset(void)
         fmChan->velocity = MAX_MIDI_VOLUME;
         fmChan->pan = 0;
         fmChan->percussive = false;
+        fmChan->pitchBend = DEFAULT_MIDI_PITCH_BEND;
     }
     synth_init(presets[0]);
 }
@@ -64,8 +67,9 @@ void midi_fm_note_on(u8 chan, u8 pitch, u8 velocity)
     fmChan->velocity = velocity;
     synth_volume(chan, effectiveVolume(fmChan));
     fmChan->pitch = pitch;
-    synth_pitch(
-        chan, midi_fm_pitchToOctave(pitch), midi_fm_pitchToFreqNumber(pitch));
+
+    u16 freq = effectiveFreq(fmChan);
+    synth_pitch(chan, midi_fm_pitchToOctave(fmChan->pitch), freq);
     synth_noteOn(chan);
 }
 
@@ -82,12 +86,18 @@ void midi_fm_channel_volume(u8 chan, u8 volume)
     synth_volume(chan, effectiveVolume(fmChan));
 }
 
+u16 effectiveFreq(MidiFmChannel* fmChan)
+{
+    u16 freq = midi_fm_pitchToFreqNumber(fmChan->pitch);
+    s16 bendRelative = fmChan->pitchBend - MIDI_PITCH_BEND_CENTRE;
+    return freq + (bendRelative / 75);
+}
+
 void midi_fm_pitch_bend(u8 chan, u16 bend)
 {
     MidiFmChannel* fmChan = &fmChannels[chan];
-    u16 freq = midi_fm_pitchToFreqNumber(fmChan->pitch);
-    s16 bendRelative = bend - MIDI_PITCH_BEND_CENTRE;
-    freq = freq + (bendRelative / 75);
+    fmChan->pitchBend = bend;
+    u16 freq = effectiveFreq(fmChan);
     synth_pitch(chan, midi_fm_pitchToOctave(fmChan->pitch), freq);
 }
 

tests/unit/main.c

@@ -98,6 +98,7 @@ int main(void)
         midi_test(test_midi_channel_volume_sets_psg_attenuation),
         midi_test(test_midi_channel_volume_sets_psg_attenuation_2),
         midi_test(test_midi_sets_synth_pitch_bend),
+        midi_test(test_midi_persists_pitch_bend_between_notes),
         midi_test(test_midi_sets_psg_pitch_bend_down),
         midi_test(test_midi_sets_psg_pitch_bend_up),
         midi_test(test_midi_psg_pitch_bend_persists_after_tick),

tests/unit/test_midi_dynamic.c

@@ -368,7 +368,6 @@ static void test_midi_dynamic_maintains_pan_on_remapping(UNUSED void** state)
 static void test_midi_dynamic_maintains_pitch_bend_on_remapping(
     UNUSED void** state)
 {
-    /* Buggy behaviour characterisation */
     const u16 midi_bend = 0x3000;
 
     // Note 1
@@ -383,8 +382,7 @@ static void test_midi_dynamic_maintains_pitch_bend_on_remapping(
 
     // Note 2
     expect_synth_pitch(1, 7, 0x295);
-    expect_synth_pitch(1, 7,
-        0x25f); // defaults back as pitch bend not taken into consideration on
+    expect_synth_pitch(1, 7, 0x295); // triggered when pitch bend "copied"
     // note on
     expect_synth_volume(1, MAX_MIDI_VOLUME);
     expect_value(__wrap_synth_noteOn, channel, 1);

tests/unit/test_midi_fm.c

@@ -452,6 +452,25 @@ static void test_midi_sets_synth_pitch_bend(UNUSED void** state)
     }
 }
 
+static void test_midi_persists_pitch_bend_between_notes(UNUSED void** state)
+{
+    for (int chan = 0; chan <= MAX_FM_CHAN; chan++) {
+        print_message("chan %d\n", chan);
+        expect_synth_pitch(chan, 4, SYNTH_NTSC_C);
+        expect_synth_volume_any();
+        expect_value(__wrap_synth_noteOn, channel, chan);
+        __real_midi_note_on(chan, 60, MAX_MIDI_VOLUME);
+
+        expect_synth_pitch(chan, 4, 0x225);
+        __real_midi_pitch_bend(chan, 1000);
+
+        expect_synth_pitch(chan, 4, 0x225);
+        expect_synth_volume_any();
+        expect_value(__wrap_synth_noteOn, channel, chan);
+        __real_midi_note_on(chan, 60, MAX_MIDI_VOLUME);
+    }
+}
+
 static void remap_midi_channel(u8 midiChannel, u8 deviceChannel)
 {
     u8 sequence[] = { SYSEX_MANU_EXTENDED, SYSEX_MANU_REGION, SYSEX_MANU_ID,