add cli option to listen for midi events

src/main.cpp

@@ -35,6 +35,7 @@ showUsage(const char* prog_name)
 	printf("Usage: %s [options]\n", prog_name);
 	printf("  options:\n");
 	printf("    -t: cycle test voltages on DAC\n");
+	printf("    -l: listen for midi events\n");
 	printf("    -k sequencer-port: attempt to connect to port \n");
 	printf("    -f midi-file: play the first track, first channel of a MIDI file\n");
 	printf("    -h: show this help \n");
@@ -109,11 +110,14 @@ main(i32 argc, char* argv[])
 	if (!midiOpen(&seq))
 		return 1;
 
-	while ((opt = getopt(argc, argv, "tk:f:h")) != -1) {
+	while ((opt = getopt(argc, argv, "tlk:f:h")) != -1) {
 		switch (opt) {
 			case 'f':
 				printf("TODO: parse and play sequence from midi file\n");
 				break;
+			case 'l':
+				loopMIDI(&seq, &spi);
+				break;
 			case 'k':
 				if (!midiConnect(&seq, optarg)) {
 					printf("Error connecting to MIDI device, %s\n", optarg);