From 9d923b5a00916478a84d21c431532e5d3065968c Mon Sep 17 00:00:00 2001
From: Jonas Gunz <himself@jonasgunz.de>
Date: Wed, 21 Jun 2017 16:16:17 +0200
Subject: Implemented MIDI interface

---
 floppyMusic/midi.c | 124 +++++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 106 insertions(+), 18 deletions(-)

(limited to 'floppyMusic/midi.c')

diff --git a/floppyMusic/midi.c b/floppyMusic/midi.c
index ff70a95..ae99371 100644
--- a/floppyMusic/midi.c
+++ b/floppyMusic/midi.c
@@ -5,38 +5,126 @@
  *  Author: Jonas
  */ 
 
+ /*
+  Octave||                     Note Numbers
+	 #  ||
+	    || C   | C#  | D   | D#  | E   | F   | F#  | G   | G#  | A   | A#  | B
+ -----------------------------------------------------------------------------
+	 0  ||   0 |   1 |   2 |   3 |   4 |   5 |   6 |   7 |   8 |   9 |  10 | 11
+	 1  ||  12 |  13 |  14 |  15 |  16 |  17 |  18 |  19 |  20 |  21 |  22 | 23
+	 2  ||  24 |  25 |  26 |  27 |  28 |  29 |  30 |  31 |  32 |  33 |  34 | 35
+	 3  ||  36 |  37 |  38 |  39 |  40 |  41 |  42 |  43 |  44 |  45 |  46 | 47
+	 4  ||  48 |  49 |  50 |  51 |  52 |  53 |  54 |  55 |  56 |  57 |  58 | 59
+	 5  ||  60 |  61 |  62 |  63 |  64 |  65 |  66 |  67 |  68 |  69 |  70 | 71
+	 6  ||  72 |  73 |  74 |  75 |  76 |  77 |  78 |  79 |  80 |  81 |  82 | 83
+	 7  ||  84 |  85 |  86 |  87 |  88 |  89 |  90 |  91 |  92 |  93 |  94 | 95
+	 8  ||  96 |  97 |  98 |  99 | 100 | 101 | 102 | 103 | 104 | 105 | 106 | 107
+	 9  || 108 | 109 | 110 | 111 | 112 | 113 | 114 | 115 | 116 | 117 | 118 | 119
+	 10 || 120 | 121 | 122 | 123 | 124 | 125 | 126 | 127 |
+ */
+
 #include "midi.h"
 
-void midi_setup()
-{
-	uart_init(9600);
-}
+extern const uint16_t midi_code_frequency_table[] = {8,9,9,10,10,11,12,12,13,14,15,15,16,17,18,19,21,22,23,25,26,28,29,31,33,35,37,39,41,44,46,49,52,55,58,62,65,69,73,78,82,87,93,98,104,110,117,123,131,139,147,156,165,175,185,196,208,220,233,247,262,277,294,311,330,349,370,392,415,440,466,494,523,554,587,622,659,698,740,784,831,880,932,988,1047,1109,1175,1245,1319,1397,1480,1568,1661,1760,1865,1976,2093,2217,2349,2489,2637,2794,2960,3136,3322,3520,3729,3951,4186,4435,4699,4978,5274,5588,5920,6272};
 
-void midi_recieve(struct midi_command *_command)
+ISR(USART_RXC_vect)
 {
-	if(!(UCSRB & (1<<RXEN))) //Return if UART reciever not enabled
-		return;
-
+	cli();
 	char status, data1, data2;
 	char command, channel, note, velocity;
 
-	status = uart_recieve();
-	data1  = uart_recieve();
-	data2  = uart_recieve();
+	//read data from interface
+	status = midi_recieve();
+	data1  = midi_recieve();
+	data2  = midi_recieve();
 
-	command = status & 0x0f; //Mask out last 4 bits 
+	sei();
+
+	//split data
+	command = status & 0x0f; //Mask out last 4 bits
 	channel = (status >> 4) & 0x0f; // Shift channel into first 4 bits;
 	note = data1;
 	velocity = data2;
 
-	_command->command = command;
-	_command->channel=channel;
-	_command->note = note;
-	_command->velocity = velocity;
+	switch(command)
+	{
+		case 0x08: //Note off
+			midi_update_note(note, 0);
+		break;
+			midi_update_note(note, 1);
+		case 0x09: //Note on
+			
+		break;
+
+		case 0x0A: //Note Fade Out
+			//unused
+		break;
+
+		case 0x0B: //Control Change
+			//unused
+		break;
+
+		case 0x0C: //Channel Fade Out
+			//unused
+		break;
+
+		case 0x0E: //Note Pitch change
+			//unused
+		break;
+	}
+	
 
 }
 
-void midi_send(struct midi_command _command)
+void midi_setup()
 {
+	midi_active_channels = 0x00;
+
+	//UART init
+	unsigned  int ubrr   = (F_CPU / (16 * _MIDI_LINK_SPEED))  - 1;
+
+	UBRRH = (unsigned char) (ubrr>>8) & 0xff;
+	UBRRL = (unsigned char) ubrr & 0xff;
+
+	UCSRB = (1<<RXEN)  | (1<<TXEN);
+	UCSRC = (1<<URSEL) | (1<<USBS) | (3<<UCSZ0);
+
+	UCSRB |= (1<<RXCIE); //enable interrupt
+}
+
+ char midi_recieve()
+ {
+	 while(!(UCSRA & (1<<RXC))); //Wait for data
+
+	 return UDR;
+ }
+
+ void midi_update_note(uint16_t _note, uint8_t _status)
+ {
+	if(_status) //Note on
+	{
+		int i;
+		for(i = 0; i < 8; i++) //search for first free channel
+			if(!(midi_active_channels & (1<<i)))
+				break;
+
+		midi_current_notes[i] = _note; //write current note to channel
+		midi_active_channels |= (1<<i); //set channel active
+		floppy_set_frequency(i, floppy_calc_freq(midi_code_frequency_table[_note]) ); //play note
+	}
 
-}
\ No newline at end of file
+	else //Note off
+	{
+		int i;
+		for(i = 0; i < 8; i++) //search for active channel playing _note
+		{
+			if(midi_current_notes[i] == _note)
+			{
+				floppy_set_frequency(i, 0); //mute
+				midi_current_notes[i] = 0xff; //unset current, 0xff is outside MIDI standards
+				midi_active_channels &= ~(1<<i); //unset channel active
+				break;
+			}
+		}
+	}
+ }
-- 
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