commit ae75b019380c9682ae68d7583f5472c9ef428934
Author: Lauchmelder <robert.altner11@gmail.com>
Date:   Fri Apr 8 19:16:55 2022 +0200

    initial commit

diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..ab3e48b
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,23 @@
+CC := gcc
+CFLAGS := -Wall -g
+LIBRARIES := -lpthread
+TARGET := musicalpi
+
+SRCS := $(wildcard src/*.c)
+OBJS := $(patsubst src/%.c, out/%.o, $(SRCS))
+
+ALL: $(TARGET)
+
+$(TARGET): mkdir $(OBJS)
+	$(CC) -o out/$@ $(filter-out $<, $^) $(LIBRARIES)
+
+mkdir:
+	mkdir -p out
+
+out/%.o: src/%.c
+	$(CC) $(CFLAGS) -c $< -o $@
+
+clean:
+	rm -rf $(TARGET) out
+
+.PHONY: all clean
diff --git a/src/main.c b/src/main.c
new file mode 100644
index 0000000..8730e37
--- /dev/null
+++ b/src/main.c
@@ -0,0 +1,143 @@
+#include <linux/soundcard.h>
+#include <stdio.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <errno.h>
+#include <string.h>
+#include <stdlib.h>
+#include <pthread.h>
+#include <stdatomic.h>
+
+static const char* devices[] = {"/dev/midi", "/dev/midi2", NULL};
+
+typedef struct Note
+{
+    unsigned char channel;
+    unsigned char pitch;
+    unsigned char velocity;
+} Note;
+
+typedef struct Offset
+{
+    signed char pitch;
+    signed char velocity
+} Offset;
+
+static const Offset pattern[] = {
+    { 0,      0 },
+    { -5,   -11 },
+    { -9,   -11 },
+    { -12,  -11 },
+    { -9,   -11 },
+    { -5,   -11 },
+    { -1,     0 },
+    { -5,   -11 },
+    { -9,   -11 },
+    { -12,  -11 },
+    { -9,   -11 },
+    { -5,   -11 },
+    { -2,     0 },
+    { -5,   -11 },
+    { -9,   -11 },
+    { -12,  -11 },
+    { -9,   -11 },
+    { -5,   -11 },
+    { -3,     0 },
+    { -5,   -11 },
+    { -9,   -11 },
+    { -12,  -11 },
+    { -9,   -11 },
+    { -5,   -11 }
+};
+
+static int _Atomic stop = ATOMIC_VAR_INIT(0);
+static int _Atomic step = ATOMIC_VAR_INIT(0);
+static Note* _Atomic note = ATOMIC_VAR_INIT(NULL);
+
+void *arpeggio_loop(void* data);
+
+int main(int argc, char** argv)
+{
+    unsigned char data[3] = {0, 0, 0};
+    int key_down = 0;
+    Note current_note;
+
+    const char* device;
+    int fd;
+    int i = 0;
+    while((device = devices[i++]) != NULL)
+    {
+        printf("Trying %s...", device);
+
+        fd = open(device, O_RDWR, 0);
+        if(fd < 0)
+        {
+            printf("Failed: %s\n", strerror(errno));
+        }
+        else
+        {
+            printf("Success!\n");
+            break;
+        }
+    }
+
+    if(fd < 0)
+    {
+        fprintf(stderr, "No MIDI devices detected.\n");
+        return -1;
+    }
+
+    printf("Using MIDI device %s\n", device);
+    pthread_t arpeggio_thread;
+    pthread_create(&arpeggio_thread, NULL, arpeggio_loop, (void*)fd);
+
+    for(;;)
+    {
+        read(fd, (void*)data, sizeof(data));
+
+        if(data[0] != 0xfd)
+        {
+            if(data[2] > 0)
+            {
+                key_down = 1;
+                note = &current_note;
+
+                current_note.channel = 0x90;
+                current_note.pitch = data[1];
+                current_note.velocity = data[2];
+            }
+            else if(data[1] == current_note.pitch)
+            {
+                key_down = 0;
+                note = NULL;
+                step = 0;
+            }
+        }
+    }
+
+    pthread_join(arpeggio_thread, NULL);
+    close(fd);
+    return 0;
+}
+
+void *arpeggio_loop(void* data)
+{
+    int fd = (int)data;
+
+    while(stop == 0)
+    {
+        if(note != NULL)
+        {
+            Note out = *note;
+            out.pitch += pattern[step].pitch;
+            out.velocity += pattern[step].velocity;
+            write(fd, &out, sizeof(Note));
+
+            step++;
+            if(step >= (sizeof(pattern) / sizeof(Offset)))
+                step = 0;
+
+            usleep(166666);
+        }
+    }
+}
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