On Fri, May 26, 2023 at 10:43 AM Oleg wrote: > Hi all, > While playing with generating audio tones (thanks for the manual > <https://www.youtube.com/watch?v=3U6OZaGnYcc>, Alan!), I wonder what I need > to write to /dev/tone to get constant signal, 100% PWM on the audio pin, > that is beep of maximum volume?
Hey there Oleg :-) Here is a documentation on how to create your own device driver and general description on how drivers work in NuttX: https://nuttx.apache.org/docs/latest/components/drivers/index.html On FreeBSD there is a /dev/speaker device handled by a kernel module that can text commands and convert them to a PC speaker tones. That could be a reference point too if you want to write a simple melody player :-) For instance this will play Star Trek tune: l2b.f+.p16a.c+.p l4mne8a2mspg+e8c+f+8b2 https://man.freebsd.org/cgi/man.cgi?query=speaker https://github.com/freebsd/freebsd-src/blob/main/sys/dev/speaker/spkr.c Applications may call ioctl(2) on a speaker file descriptor to control the speaker driver directly; definitions for the ioctl(2) interface are in <dev/speaker/speaker.h>. The 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 ioctl(2) calls. SPKRTONE accepts a pointer to a single tone structure as third argument and plays it. SPKRTUNE ac- cepts 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 modeled on the PLAY statement conventions of IBM Advanced BASIC 2.0. The MB, MF, and X primitives of PLAY are not useful in a timesharing environment and are omitted. The `octave-track- ing' feature and the slur mark are new. There are 84 accessible notes numbered 1-84 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: CDEFGAB Letters A through G cause the corresponding note to be played in the current octave. A note letter may optionally be fol- lowed 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 val- ues 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 dis- abled 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 >, < and O[0123456]. (The octave-locking feature is not supported in IBM BASIC.) > 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 or crotchet 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 n. 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: Tempo Beats Per Minute very slow Larghissimo Largo 40-60 Larghetto 60-66 Grave Lento Adagio 66-76 slow Adagietto Andante 76-108 medium Andantino Moderato 108-120 fast Allegretto Allegro 120-168 Vivace Veloce Presto 168-208 very fast Prestissimo M[LNS] 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 for 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 un- dotted value; dotted twice, it is held 9/4, and three times would give 27/8. A note and its sustain dots may also be followed by a slur mark (under- score). This causes the normal micro-rest after the note to be filled in, slurring it to the next one. (The slur feature is not supported in IBM BASIC.) Whitespace in play strings is simply skipped and may be used to separate melody sections. -- CeDeROM, SQ7MHZ, http://www.tomek.cedro.info
