add cli option to connect to midi device

src/main.cpp

@@ -1,4 +1,8 @@
 
+#include <cstdio>
+#include <cstdlib>
+
+#include <unistd.h>
 #include <linux/spi/spi.h>
 
 #include "spi.h"
@@ -15,6 +19,21 @@
 
 #define MAX_DAC_INPUT 4095 // 2^12 - 1
 
+
+void
+showUsage(const char* prog_name)
+{
+	printf("Usage: %s [options]\n", prog_name);
+	printf("  options:\n");
+	printf("    -t: cycle test voltages on DAC\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");
+	printf("  example:\n");
+	printf("    %s -k 20:0\n", prog_name);
+	printf("    attempt to connect to MIDI input device on channel:port 20:0\n");
+}
+
 u32
 convertNoteToDACInput(u8 midi_note)
 {
@@ -28,11 +47,34 @@ convertNoteToDACInput(u8 midi_note)
 	return dac;
 }
 
-// TODO: add an argument option that slowly cycles between 0-1V for tuning an
-// 	oscillator
+void
+loopMIDI(alsa_sequencer* seq, spi_connection* spi)
+{
+	while(1)
+	{
+		printf("\n--------------------\n");
+		snd_seq_event_t *ev = nullptr;
+		snd_seq_event_input(seq->seq_handle, &ev);
+		i32 note = midiProcess(ev);
+
+		if (note >= 0) {
+			i32 dac_in = convertNoteToDACInput(note);
+
+			// TODO: could check return value here for SPI error
+			spiSendVoltage(spi, dac_in);
+		}
+	}
+}
+
 i32
-main()
+main(i32 argc, char* argv[])
 {
+	if (argc == 1) {
+		showUsage(argv[0]);
+		exit(0);
+	}
+
+	i32 opt = 0;
 	alsa_sequencer seq = {0};
 	u8 spi_buf[SPI_BUFFER_LENGTH] = {0};
 	spi_connection spi = spiInit(SPI_SPEED, MAX_DAC_INPUT, spi_buf, SPI_BUFFER_LENGTH, SPI_FLAGS, SPI_CHANNEL);
@@ -45,20 +87,30 @@ main()
 	if (!midiOpen(&seq))
 		return 1;
 
-	while(1)
-	{
-		printf("\n--------------------\n");
-		snd_seq_event_t *ev = nullptr;
-		snd_seq_event_input(seq.seq_handle, &ev);
-		i32 note = midiProcess(ev);
-
-		if (note > 0) {
-			i32 dac_in = convertNoteToDACInput(note);
+	while ((opt = getopt(argc, argv, "tk:f:h")) != -1) {
+		switch (opt) {
+			case 'f':
+				printf("TODO: parse and play sequence from midi file\n");
+				break;
+			case 'k':
+				if (!midiConnect(&seq, optarg)) {
+					printf("Error connecting to MIDI device, %s\n", optarg);
+					exit(1);
+				}
 
-			// TODO: could check return value here for SPI error
-			spiSendVoltage(&spi, dac_in);
+				loopMIDI(&seq, &spi);
+				break;
+			case 't':
+				printf("TODO: cycle test voltages to SPI DAC\n");
+				break;
+			case 'h':
+			default:
+				showUsage(argv[0]);
+				exit(1);
 		}
 	}
 
+	midiClose(&seq);
 	return spiClose(spi.fd);
 }
+

src/midi.cpp

@@ -1,9 +1,18 @@
 
+#include <cassert>
 #include <cmath>
+#include <string>
 
 #include "midi.h"
 
 
+// forward declarations
+
+bool parseDeviceStr(snd_seq_addr_t& src, const char* midi_device);
+
+
+// interface
+
 bool
 midiOpen(alsa_sequencer* seq)
 {
@@ -12,27 +21,48 @@ midiOpen(alsa_sequencer* seq)
 		return false;
 	}
 
-	if (snd_seq_set_client_name(seq->seq_handle, "Midi Listener")) {
+	if (snd_seq_set_client_name(seq->seq_handle, "midi_to_cv")) {
 		printf("Could not set client name\n");
 		return false;
 	}
 
-	seq->in_port = snd_seq_create_simple_port(seq->seq_handle,
+	seq->dest.client = snd_seq_client_id(seq->seq_handle);
+	seq->dest.port = snd_seq_create_simple_port(seq->seq_handle,
 		"listen:in",
 		SND_SEQ_PORT_CAP_WRITE|SND_SEQ_PORT_CAP_SUBS_WRITE,
 		SND_SEQ_PORT_TYPE_APPLICATION);
 
-	if (seq->in_port < 0) {
+	if (seq->dest.port < 0) {
 		printf("Could not open port\n");
 		return false;
 	}
 
-	i32 client_id = snd_seq_client_id(seq->seq_handle);
-	printf("client id: %d, MIDI port: %d\n", client_id, seq->in_port);
+	printf("host client id: %d, host port: %d\n", seq->dest.client, seq->dest.port);
 
 	return true;
 }
 
+bool
+midiConnect(alsa_sequencer* seq, const char* midi_device)
+{
+	if (!parseDeviceStr(seq->src, midi_device)) {
+		printf("invalid device string\n");
+		return false;
+	}
+
+	snd_seq_port_subscribe_malloc(&seq->subscription);
+	snd_seq_port_subscribe_set_sender(seq->subscription, &seq->src);
+	snd_seq_port_subscribe_set_dest(seq->subscription, &seq->dest);
+	snd_seq_port_subscribe_set_queue(seq->subscription, 1);
+	snd_seq_port_subscribe_set_time_update(seq->subscription, 1);
+	snd_seq_port_subscribe_set_time_real(seq->subscription, 1);
+
+	if (snd_seq_subscribe_port(seq->seq_handle, seq->subscription) == 0)
+		return true;
+
+	return false;
+}
+
 i32
 midiProcess(const snd_seq_event_t* ev)
 {
@@ -64,3 +94,43 @@ midiProcess(const snd_seq_event_t* ev)
 
 	return note;
 }
+
+i32
+midiClose(alsa_sequencer* seq)
+{
+	snd_seq_port_subscribe_free(seq->subscription);
+	return snd_seq_close(seq->seq_handle);
+}
+
+
+// internal
+
+bool
+parseDeviceStr(snd_seq_addr_t& src, const char* midi_device)
+{
+	// NOTE: midi_device should be in the form 'client:port', where each number
+	// is an unsigned char. So max string length is 'xxx:xxx" = 7
+	std::string s(midi_device);
+
+	if (s.size() > 0 && s.size() < 8) {
+		u32 split = s.find(':');
+
+		if (split > 0 && split != std::string::npos) {
+			std::string sub1 = s.substr(0, split);
+			std::string sub2 = s.substr(split + 1, s.size());
+
+			u32 client= strtoul(sub1.c_str(), nullptr, 10);
+			u32 port = strtoul(sub2.c_str(), nullptr, 10);
+
+			if (errno == 0 && client > 0 && client < 256 && port >= 0 && port < 256)
+			{
+				src.client = client;
+				src.port = port;
+				return true;
+			}
+		}
+	}
+
+	return false;
+}
+

src/midi.h

@@ -9,10 +9,16 @@
 struct alsa_sequencer
 {
 	snd_seq_t* seq_handle;
-	i32 in_port;
+	snd_seq_port_subscribe_t* subscription;
+	snd_seq_addr_t src;
+	snd_seq_addr_t dest;
 };
 
 
-bool midiOpen(alsa_sequencer* handles);
+bool midiOpen(alsa_sequencer* seq);
+
+bool midiConnect(alsa_sequencer* seq, const char* midi_device);
 
 i32 midiProcess(const snd_seq_event_t* ev);
+
+i32 midiClose(alsa_sequencer* seq);