c/ghetto-sound-system/midi-rx.c

   1 /* Modified code from http://tldp.org/HOWTO/MIDI-HOWTO-9.html
   2  * This will print ALSA-Seq (MIDI) events to stdout for further processing eg.: in Arduino
   3  */
   4
   5 #include <stdio.h>
   6 #include <stdlib.h>
   7 #include <unistd.h>
   8 #include <alsa/asoundlib.h>
   9
  10 #define MIDI_NOTE_OFF   128
  11 #define MIDI_NOTE_ON    144
  12 #define MIDI_CONTROL    176
  13 #define MIDI_PITCH_BEND 224
  14 #define MIDI_FORMAT     "%c%c%c"
  15 #define MIDI_FORMAT_ERR "%d:%d:%d\n"
  16
  17 snd_seq_t *open_seq();
  18 void midi_action(snd_seq_t *seq_handle);
  19
  20 snd_seq_t *open_seq() {
  21
  22   snd_seq_t *seq_handle;
  23   int portid;
  24
  25   if (snd_seq_open(&seq_handle, "hw", SND_SEQ_OPEN_DUPLEX, 0) < 0) {
  26     fprintf(stderr, "Error opening ALSA sequencer.\n");
  27     exit(1);
  28   }
  29   snd_seq_set_client_name(seq_handle, "ALSA Sequencer Pipe");
  30   if ((portid = snd_seq_create_simple_port(seq_handle, "ALSA Sequencer Pipe",
  31             SND_SEQ_PORT_CAP_WRITE|SND_SEQ_PORT_CAP_SUBS_WRITE,
  32             SND_SEQ_PORT_TYPE_APPLICATION)) < 0) {
  33     fprintf(stderr, "Error creating sequencer port.\n");
  34     exit(1);
  35   }
  36   return(seq_handle);
  37 }
  38
  39 void midi_action(snd_seq_t *seq_handle) {
  40
  41   snd_seq_event_t *ev;
  42
  43   do {
  44     snd_seq_event_input(seq_handle, &ev);
  45     switch (ev->type) {
  46       case SND_SEQ_EVENT_CONTROLLER:
  47         printf(MIDI_FORMAT, MIDI_CONTROL, ev->data.control.channel, ev->data.control.value);
  48         break;
  49       case SND_SEQ_EVENT_PITCHBEND:
  50         printf(MIDI_FORMAT, MIDI_PITCH_BEND, ev->data.control.channel, ev->data.control.value);
  51         break;
  52       case SND_SEQ_EVENT_NOTEON:
  53         printf(MIDI_FORMAT, MIDI_NOTE_ON, ev->data.control.channel, ev->data.note.note);
  54         break;
  55       case SND_SEQ_EVENT_NOTEOFF:
  56         printf(MIDI_FORMAT, MIDI_NOTE_OFF, ev->data.control.channel, ev->data.note.note);
  57         break;
  58     }
  59                 fflush(stdout); fflush(stderr);
  60     snd_seq_free_event(ev);
  61   } while (snd_seq_event_input_pending(seq_handle, 0) > 0);
  62 }
  63
  64 int main(int argc, char *argv[]) {
  65
  66   snd_seq_t *seq_handle;
  67   int npfd;
  68   struct pollfd *pfd;
  69
  70   seq_handle = open_seq();
  71   npfd = snd_seq_poll_descriptors_count(seq_handle, POLLIN);
  72   pfd = (struct pollfd *)alloca(npfd * sizeof(struct pollfd));
  73   snd_seq_poll_descriptors(seq_handle, pfd, npfd, POLLIN);
  74
  75         fprintf(stderr, "COMMAND:CHANNEL:NOTE\nCommands are described on http://www.ec.vanderbilt.edu/computermusic/musc216site/MIDI.Commands.html\n\n");
  76   while (1) {
  77     if (poll(pfd, npfd, 100000) > 0) {
  78       midi_action(seq_handle);
  79     }
  80   }
  81 }