//Author HiSER (c)2010

#include <mega8.h>
#include <delay.h>

#define Q_FREQ 8000000
#define CS_PIN PORTB.2

#asm
#define SD_DI 0x18,1
#define SD_DO 0x16,4
#define SD_CLK 0x18,5
#endasm

typedef unsigned char byte;
typedef unsigned int word;
typedef unsigned long ulong;

byte buff[256];
word pbuff=0;
byte udbuff=0;
ulong wavesize;
ulong lba=0;
byte ch=0;
byte sdi=0;

interrupt [TIM1_CAPT] void timer1_capt_isr(void) {
if (pbuff==0||pbuff==128) udbuff=1;
#asm
push r26
push r27  
push r25  
clr r25  
ldi r26,low(_buff)
ldi r27,high(_buff)
add r26,_pbuff
adc r27,r25  
ld r25,X
out 0x23,r25
pop r25
pop r27
pop r26
inc _pbuff
#endasm
}

byte spi(byte v) {
#asm
ld r30,Y
push r22
ldi r22,8
__next_bit:
sbrc r30,7
sbi SD_DI
sbrs r30,7
cbi SD_DI
sbi SD_CLK
lsl r30
sbic SD_DO
sbr r30,1
cbi SD_CLK
dec r22
brne __next_bit
pop r22
#endasm
}

byte sd_init() {
byte i;
CS_PIN=1;
delay_ms(5);
for (i=0;i<10;i++) spi(0xff);
CS_PIN=0;
delay_ms(5);
spi(0x40);
spi(0);
spi(0);
spi(0);
spi(0);
spi(0x95);
spi(0xff);
if (spi(0xff)!=1) return 0;
i=0;
do {
spi(0x41);
spi(0);
spi(0);
spi(0);
spi(0);
spi(0xff);
spi(0xff);
delay_us(10);
i++;
if (i==0) return 0;
} while (spi(0xff)!=0);
spi(0x50);
spi(0);
spi(0);
spi(2);
spi(0);
spi(0xff);
spi(0xff);
spi(0xff);
return 1;
}

byte sd_read() {
word i=0;
spi(0x51);
spi((byte)(lba>>24));
spi((byte)(lba>>16));
spi((byte)(lba>>8));
spi((byte)lba);
spi(0xff);
spi(0xff);
if (spi(0xff)!=0) return 0;
while (spi(0xff)!=0xfe&&i<255) i++;
if (i==255) return 0;
return 1;
}

byte play() {
word i;
lba=0;
sdi=sd_read();
if (sdi==0) return 0;
for (i=0;i<128;i++) buff[i]=spi(0xff);
pbuff=44;
ch=1;
udbuff=1;
lba+=512;
if (buff[20]!=1&&buff[21]!=0) return 0;
wavesize=buff[24];
wavesize|=(ulong)buff[25]<<8;
wavesize|=(ulong)buff[26]<<16;
wavesize|=(ulong)buff[27]<<24;
if (wavesize<8000||wavesize>48000) {
return 0;
}else{
wavesize=Q_FREQ/wavesize;
ICR1H=(byte)(wavesize>>8);
ICR1L=(byte)wavesize;
}
wavesize=buff[40];
wavesize|=(ulong)buff[41]<<8;
wavesize|=(ulong)buff[42]<<16;
wavesize|=(ulong)buff[43]<<24;
wavesize-=84;
TCNT1H=0;
TCNT1L=0;
TCCR1A=0;
TCCR1B=0x19;
TCNT2=0;
return 1;
}

void stop() {
TCCR1A=0;
TCCR1B=0;
OCR2=0x80;
}

void playlooping() {
word i;
if (udbuff!=0&&sdi!=0) {
if (wavesize>127) wavesize-=128; else wavesize=0;
if (wavesize==0) {
stop();
play();
return;
}
if (pbuff<128) {
for (i=128;i<256;i++) buff[i]=spi(0xff);
}else{
for (i=0;i<128;i++) buff[i]=spi(0xff);
}
udbuff=0;
ch++;
if (ch==4) {
spi(0xff);
spi(0xff);
lba+=512;
sdi=sd_read();
ch=0;
}
}
}

void avr_init() {
PORTB=0x10;
DDRB=0x2e;
TCCR1A=0;
TCCR1B=0;
TCNT1H=0;
TCNT1L=0;
ICR1H=0;
ICR1L=0;
ASSR=0x00;
TCCR2=0x69;
TCNT2=0x00;
OCR2=0x80;
TIMSK=0x20;
}

void main(void) {
avr_init();
#asm("sei")
while (1) {
if (sdi==0) {
stop();
sdi=sd_init();
if (sdi!=0) sdi=play();
}else{
playlooping();
}
}
}