test/midi_int.c

   1 #include <avr/io.h>
   2 #include <avr/interrupt.h>
   3 #include <avr/eeprom.h>
   4 #include <stdio.h>
   5 #include "midi.h"
   6
   7 #define false 0
   8 #define true 1
   9
  10 #define MIDI_SYSEX_MAX_LEN 64
  11 volatile uint8_t sysex_buf_len = 0;
  12 volatile uint8_t sysex_buf[MIDI_SYSEX_MAX_LEN];
  13
  14 volatile uint8_t sysex_read = false;
  15 volatile int16_t midisync_clocked = 0;
  16
  17 #define IN_MIDI_Q_SIZE 32
  18 #define OUT_MIDI_Q_SIZE 32
  19
  20 volatile uint8_t in_midi_q[IN_MIDI_Q_SIZE];  // cyclic queue for midi msgs
  21 volatile static uint8_t in_head_idx = 0;
  22 volatile static uint8_t in_tail_idx = 0;
  23 volatile uint8_t out_midi_q[OUT_MIDI_Q_SIZE];// cyclic queue for midi msgs
  24 volatile static uint8_t out_head_idx = 0;
  25 volatile static uint8_t out_tail_idx = 0;
  26
  27 #define MIDI_BAUDRATE 31250UL       // the MIDI spec baudrate
  28
  29 uint8_t EEMEM ee_midi_channel = 0;
  30
  31 void midi_handle_sysex(void);
  32
  33 // interrupt on receive char
  34 ISR(SIG_USART0_RECV) {
  35         uint8_t c = UDR0;
  36
  37         if( c == MD_SYSEX_START ) {
  38                 sysex_read = true;
  39                 sysex_buf_len = 0;
  40         } else if( c == MD_SYSEX_END ) {
  41                 midi_handle_sysex();
  42                 sysex_read = false;
  43         }
  44
  45         if( sysex_read ) {
  46                 sysex_buf[ sysex_buf_len++ ] = c;
  47         } else {
  48                 in_midi_q[in_tail_idx++] = c;    // place at end of q
  49                 in_tail_idx %= IN_MIDI_Q_SIZE;
  50
  51                 if( in_tail_idx == in_head_idx ) {
  52                         // i.e. there are too many msgs in the q
  53                         // drop the oldest msg?
  54                         in_head_idx++;
  55                         in_head_idx %= IN_MIDI_Q_SIZE;
  56                 }
  57         }
  58 }
  59
  60 ISR(SIG_USART0_DATA) {
  61         if( out_tail_idx != out_head_idx ) {
  62                 UDR0 = out_midi_q[out_tail_idx++];
  63                 out_tail_idx %= OUT_MIDI_Q_SIZE;
  64
  65                 // output buffer empty
  66                 if( out_tail_idx == out_head_idx )
  67                         UCSR0B &= ~_BV(UDRIE0);
  68         }
  69 }
  70
  71 ISR(SIG_USART0_TRANS) {
  72
  73 }
  74
  75 void midi_init(void) {
  76         // read and write, interrupt on recv.
  77         UCSR0B |= (1<<RXEN0) | (1<<TXEN0)| (1<<RXCIE0) | (1<<TXCIE0);
  78
  79         /* setup the MIDI UART */
  80         uint16_t ubbr = (F_CPU / (16 * MIDI_BAUDRATE)) - 1;     // formula in datasheet
  81         UBRR0L = (uint8_t)ubbr;               // set baudrate
  82         UBRR0H = (uint8_t)(ubbr>>8);
  83 }
  84
  85 int midi_putchar(uint8_t c) {
  86         while( (out_head_idx+1)%OUT_MIDI_Q_SIZE == out_tail_idx );
  87
  88         cli();
  89         {
  90                 // Add it to the queue
  91                 out_midi_q[out_head_idx++] = c;
  92                 out_head_idx %= OUT_MIDI_Q_SIZE;
  93
  94                 UCSR0B |= _BV(UDRIE0);
  95         }
  96         sei();
  97         return 0;
  98 }
  99
 100 int midi_getch(void) {     // checks if there is a character waiting!
 101         if( in_head_idx != in_tail_idx )
 102                 return 1;
 103         return 0;
 104 }
 105
 106 int midi_getchar(void) {
 107         char c;
 108
 109         while( in_head_idx == in_tail_idx );
 110
 111         cli();
 112         {
 113                 c = in_midi_q[in_head_idx++];
 114                 in_head_idx %= IN_MIDI_Q_SIZE;
 115         }
 116         sei();
 117
 118         return c;
 119 }
 120
 121 void midi_send(uint8_t status, uint8_t chan, uint8_t data, uint8_t data2) {
 122         midi_putchar( (status & 0xF0)|(chan & 0x0F) );
 123         midi_putchar( data & 0x7F );
 124         midi_putchar( data2 & 0x7F );
 125 }
 126
 127 static uint8_t SYSEX_snd_checksum;
 128 void sysex_start(uint8_t command) {
 129         // Reset checksum
 130         SYSEX_snd_checksum = 0;
 131
 132         // Send SYSEX start, manufacturer ID, model number and command
 133         midi_putchar(MD_SYSEX_START);
 134         midi_putchar(MD_MF_ID_1);
 135         midi_putchar(MD_MF_ID_2);
 136         midi_putchar(MD_MF_ID_3);
 137         midi_putchar(MD_SYNTH_ID);
 138         midi_putchar(command);
 139 }
 140
 141 void sysex_data(uint8_t data) {
 142         // split one byte of data in two
 143         uint8_t msb = data >> 7;
 144         uint8_t lsb = data & 0x7f;
 145         midi_putchar(msb);
 146         midi_putchar(lsb);
 147
 148         SYSEX_snd_checksum = (SYSEX_snd_checksum + msb + lsb) & 0x7F;
 149 }
 150
 151 void sysex_end(void) {
 152         // Send checksum
 153         midi_putchar(SYSEX_snd_checksum);
 154
 155         // Send end of SYSEX
 156         midi_putchar(MD_SYSEX_END);
 157 }
 158
 159 uint8_t calcCRC(void) {
 160         uint8_t i, crc = 0;
 161         for(i = 0; i < sysex_buf_len; ++i)
 162                 crc = (crc + sysex_buf[i]) & 0x7F;
 163         return crc;
 164 }
 165
 166 void midi_handle_sysex(void) {
 167         uint8_t crc = sysex_buf[ sysex_buf_len-1];
 168         sysex_buf_len--;
 169
 170         // check crc
 171         if( crc != calcCRC() ) {
 172                 sysex_buf_len = 0;
 173                 return;
 174         }
 175
 176         if( (sysex_buf_len < 5) ||
 177                         sysex_buf[0] != MD_MF_ID_1 ||
 178                         sysex_buf[1] != MD_MF_ID_2 ||
 179                         sysex_buf[2] != MD_MF_ID_3 ||
 180                         sysex_buf[3] != MD_SYNTH_ID ) {
 181                 sysex_buf_len = 0;
 182                 return;
 183         }
 184
 185         //handle_sysex(sysex_buf+4, sysex_buf_len);
 186 }
 187
 188 uint8_t midi_readchannel(void) {
 189         return eeprom_read_byte( &ee_midi_channel );
 190 }
 191