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     "%d:%d:%d\n"
  15
  16 snd_seq_t *open_seq();
  17 void midi_action(snd_seq_t *seq_handle);
  18
  19 snd_seq_t *open_seq() {
  20
  21   snd_seq_t *seq_handle;
  22   int portid;
  23
  24   if (snd_seq_open(&seq_handle, "hw", SND_SEQ_OPEN_DUPLEX, 0) < 0) {
  25     fprintf(stderr, "Error opening ALSA sequencer.\n");
  26     exit(1);
  27   }
  28   snd_seq_set_client_name(seq_handle, "ALSA Sequencer Pipe");
  29   if ((portid = snd_seq_create_simple_port(seq_handle, "ALSA Sequencer Pipe",
  30             SND_SEQ_PORT_CAP_WRITE|SND_SEQ_PORT_CAP_SUBS_WRITE,
  31             SND_SEQ_PORT_TYPE_APPLICATION)) < 0) {
  32     fprintf(stderr, "Error creating sequencer port.\n");
  33     exit(1);
  34   }
  35   return(seq_handle);
  36 }
  37
  38 void midi_action(snd_seq_t *seq_handle) {
  39
  40   snd_seq_event_t *ev;
  41
  42   do {
  43     snd_seq_event_input(seq_handle, &ev);
  44     switch (ev->type) {
  45       case SND_SEQ_EVENT_CONTROLLER:
  46         printf(MIDI_FORMAT, MIDI_CONTROL, ev->data.control.channel, ev->data.control.value);
  47         break;
  48       case SND_SEQ_EVENT_PITCHBEND:
  49         printf(MIDI_FORMAT, MIDI_PITCH_BEND, ev->data.control.channel, ev->data.control.value);
  50         break;
  51       case SND_SEQ_EVENT_NOTEON:
  52         printf(MIDI_FORMAT, MIDI_NOTE_ON, ev->data.control.channel, ev->data.note.note);
  53         break;
  54       case SND_SEQ_EVENT_NOTEOFF:
  55         printf(MIDI_FORMAT, MIDI_NOTE_OFF, ev->data.control.channel, ev->data.note.note);
  56         break;
  57     }
  58     snd_seq_free_event(ev);
  59   } while (snd_seq_event_input_pending(seq_handle, 0) > 0);
  60 }
  61
  62 int main(int argc, char *argv[]) {
  63
  64   snd_seq_t *seq_handle;
  65   int npfd;
  66   struct pollfd *pfd;
  67
  68   seq_handle = open_seq();
  69   npfd = snd_seq_poll_descriptors_count(seq_handle, POLLIN);
  70   pfd = (struct pollfd *)alloca(npfd * sizeof(struct pollfd));
  71   snd_seq_poll_descriptors(seq_handle, pfd, npfd, POLLIN);
  72
  73         fprintf(stderr, "COMMAND:CHANNEL:NOTE\nCommands are described on http://www.ec.vanderbilt.edu/computermusic/musc216site/MIDI.Commands.html\n\n");
  74   while (1) {
  75     if (poll(pfd, npfd, 100000) > 0) {
  76       midi_action(seq_handle);
  77     }
  78   }
  79 }