Module speaker 

PC Speaker driver : beep codes + music playback.

Hardware: PIT channel 2 (port 0x42) generates a square wave, port 0x61 bits 0-1 gate the speaker on/off.

Two modes:

1. Blocking (boot): beep() busy-waits : used before scheduler.
2. Music (runtime): note queue drained by PIT timer interrupt.

Structs

Note

A musical note: frequency in Hz and duration code. Duration codes map to note lengths at a given tempo.

Constants

END

ERROR_DURS

ERROR_NOTES

Error / failure tone.

IMPERIAL_MARCH_DURS

IMPERIAL_MARCH_NOTES

The Imperial March (Star Wars) : for panic screens. Notes: (freq Hz, duration code)

PIT_CHANNEL2_CMD 🔒

PIT_FREQ 🔒

REST

Special frequency values.

SPEAKER_DATA_BIT 🔒

SPEAKER_GATE_BIT 🔒

STARTUP_DURS

STARTUP_NOTES

Startup jingle (ascending arpeggio).

Statics

MUSIC_PLAYING 🔒

NOTE_DUR_PTR 🔒

Pointer to the duration array (in milliseconds).

NOTE_FREQ 🔒

Current note frequency (Hz). Updated by the music player on timer tick.

NOTE_INDEX 🔒

Index into the current note sequence.

NOTE_SEQ_PTR 🔒

Pointer to the note sequence array (freq in Hz).

NOTE_TICKS_LEFT 🔒

Remaining ticks for the current note.

NOTE_TOTAL 🔒

Total number of notes in the current sequence.

SPEAKER_ACTIVE 🔒

TEMPO 🔒

Tempo multiplier (100 = normal, 200 = double speed, 50 = half speed).

Functions

beep

Play a tone at freq Hz for ms milliseconds. Blocks via PIT busy-wait.

beep_fail

Long beep : critical failure.

beep_off

Silence the speaker immediately.

beep_ok

Short beep : milestone reached.

beep_panic

Panic melody : descending notes.

beep_phase

Play a crescendo beep for boot phase N. Each successive phase uses a higher frequency so you can identify the last completed phase by pitch alone.

beep_startup

Startup jingle : ascending notes (happy boot).

beep_warn

Double beep : warning.

music_playing

Returns whether music is currently playing.

music_start^⚠

Start playing a note sequence. Non-blocking : drained by speaker_tick().

music_stop

Stop music playback.

pit_busy_wait 🔒

Busy-wait for ms milliseconds using PIT channel 2 (mode 0, one-shot). Works before the APIC timer / scheduler are running.

pit_set_freq 🔒 ^⚠

Set the PIT channel 2 frequency. hz = 0 disables the tone.

speaker_enable 🔒 ^⚠

Enable or disable the speaker output.

speaker_tick

Call this from the PIT timer interrupt (~10ms tick) to advance music playback.