console speaker device
spkr0 at pcppi?
speaker device driver allows
applications to control the built-in speaker on machines providing a PCPPI
Only one process may have this device open at any given
time; open(2) and
close(2) are used to lock and relinquish it. An attempt to
another process has the device locked will return -1 with an
EBUSY error indication. Writes to the device are
interpreted as “play strings” in a simple ASCII melody
ioctl() for tone generation at
arbitrary frequencies is also supported.
Sound-generation does not monopolize the processor; in fact, the driver spends most of its time sleeping while the PC hardware is emitting tones. Other processes may emit beeps while the driver is running.
Applications may call
ioctl() on a
speaker file descriptor to control the speaker driver directly; definitions
ioctl() interface are in
tone_t structure used in these calls has two fields,
specifying a frequency (in Hz) and a duration (in 1/100ths of a second). A
frequency of zero is interpreted as a rest.
At present there are two such ioctls. The
SPKRTONE ioctl accepts a pointer to a single tone
structure as a third argument and plays it. The
SPKRTUNE ioctl accepts a pointer to the first of an
array of tone structures and plays them in continuous sequence; this array
must be terminated by a final member with a zero duration.
The play-string language is modelled on the PLAY statement conventions of IBM BASIC 2.0. The MB, MF and X primitives of PLAY are not useful in a UNIX environment and are omitted. The “octave-tracking” feature is also new.
There are 84 accessible notes numbered 1-83 in 7 octaves, each running from C to B, numbered 0-6; the scale is equal-tempered A440 and octave 3 starts with middle C. By default, the play function emits half-second notes with the last 1/16th second being “rest time”.
Play strings are interpreted left to right as a series of play command groups; letter case is ignored. Play command groups are as follows:
- Letters A through G cause the corresponding note to be played in the
current octave. A note letter may optionally be followed by an
“accidental sign”, one of
+’, or ‘
-’; the first two of these cause it to be sharped one half-tone, the last causes it to be flatted one half-tone. It may also be followed by a time value number and by sustain dots (see below). Time values are interpreted as for the L command below;.
- O ⟨n⟩
- If n is numeric, this sets the current octave.
n may also be one of ‘L’ or
‘N’ to enable or disable octave-tracking (it is disabled by
default). When octave-tracking is on, interpretation of a pair of letter
notes will change octaves if necessary in order to make the smallest
possible jump between notes. Thus "olbc" will be played as
"olb>c", and "olcb" as "olc<b". Octave
locking is disabled for one letter note following by
<’, and ‘
> -- bump the current octave up one. < -- drop the current octave down one.
- N ⟨n⟩
- Play note n, n being 1 to 84 or 0 for a rest of current time value. May be followed by sustain dots.
- L ⟨n⟩
- Sets the current time value for notes. The default is L4, quarter notes. The lowest possible value is 1; values up to 64 are accepted. L1 sets whole notes, L2 sets half notes, L4 sets quarter notes, etc.
- P ⟨n⟩
- Pause (rest), with n interpreted as for L. May be
followed by sustain dots. May also be written
- T ⟨n⟩
- Sets the number of quarter notes per minute; default is 120. Musical names
for common tempi are:
Description Tempo Beats per Minute very slow Larghissimo 40–60 very slow Largo 40–60 very slow Larghetto 60–66 very slow Grave 60–66 very slow Lento 60–66 slow Adagio 66–76 slow Adagietto 66–76 medium Andante 76–108 medium Andantino 76–108 fast Moderato 108–120 fast Allegretto 108–120 fast Allegro 120–168 fast Vivace 120–168 fast Veloce 120–168 very fast Presto 168–208 very fast Prestissimo 168–208
- Set articulation. MN (N for normal) is the default; the last 1/8th of the note's value is rest time. You can set ML for legato (no rest space) or MS (staccato) 1/4 rest space.
Notes (that is, CDEFGAB or N command character groups) may be followed by sustain dots. Each dot causes the note's value to be lengthened by one-half for each one. Thus, a note dotted once is held for 3/2 of its undotted value; dotted twice, it is held 9/4, and three times would give 27/8.
Whitespace in play strings is simply skipped and may be used to separate melody sections.
Eric S. Raymond ⟨email@example.com⟩, Feb 1990
Due to roundoff in the pitch tables and slop in the tone-generation and timer hardware (neither of which was designed for precision), neither pitch accuracy nor timings will be mathematically exact.
There is no volume control.
In play strings which are very long (longer than your system's physical I/O blocks) note suffixes or numbers may occasionally be parsed incorrectly due to crossing a block boundary.