console speaker device driver
spkr0 at pcppi?
device driver allows applications to
control the built-in speaker on machines providing a PCPPI speaker interface.
Only one process may have this device open at any given time;
are used to lock and
relinquish it. An attempt to open
() when another
process has the device locked will return -1 with an
error indication. Writes to the
device are interpreted as “play strings” in a simple ASCII
melody notation. An 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 for the
() interface are in
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
ioctl accepts a pointer to a
single tone structure as a third argument and plays it. The
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
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
-’; 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
- 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
> -- bump the current octave up one.
< -- drop the current octave down one.
- Play note n,
n being 1 to 84 or 0 for a rest of
current time value. May be followed by sustain dots.
- 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,
- Pause (rest), with n
interpreted as for L. May be followed by sustain dots. May also be written
- Sets the number of quarter notes per minute; default is
120. Musical names for common tempi are:
||Beats per Minute
- 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
Eric S. Raymond
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.