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#include <avr/io.h>
#include <avr/delay.h>
static char buffer[300];
#define OUT0 "sbi %2, 5 \n" /* pull line to GND */
#define OUT1 "cbi %2, 5 \n" /* tristate the line */
#define WAIT10 "ldi r16, 1 \n rcall delay_loop \n"
#define WAIT34 "ldi r16, 9 \n rcall delay_loop \n"
#define WAIT10MINUS10 ""
#define WAIT34MINUS10 "ldi r16,5 \n rcall delay_loop \n nop \n nop \n"
int send_recv_gc(char* bytes, int len)
{
char* buf_ptr = buffer;
/****** SEND PART ******/
int k=0;
for (int i=0; i<len; i++)
for (int j=0x80; j!=0; j=j>>1, k++)
buffer[k] = ((bytes[i] & j)!=0)?1:0 ;
len=len*8+1;
asm volatile(
"push r31 ; save Z\n"
"push r30 \n\n"
";;;;;;;; SEND PART ;;;;;;;;\n\n"
"send_loop: \n"
"sbiw %3, 1 \n" // 2
"breq send_done \n" // 1 if not done, 2 if done
"ld r16, z+ \n" // 2
"tst r16 \n" // 1
"brne send_one \n\n" // 1 if zero, 2 if nonzero
"; otherwise, send zero \n"
"nop \n" // 1
OUT0
WAIT34
OUT1
WAIT10MINUS10
"rjmp send_loop \n\n" // 2
"send_one: \n"
OUT0
WAIT10
OUT1
WAIT34MINUS10
"rjmp send_loop \n\n"
"delay_loop:\n"
"; this costs 7 + 3*(r16) cycles \n"
"dec r16\n"
"brne delay_loop\n"
"ret\n\n"
"send_done: \n"
"; now send the stop bit and release the line \n"
"nop \n nop \n nop \n"
OUT0
"; instead of WAIT10, do sensible work \n"
"pop r30 ; restore Z \n" // 2
"pop r31 \n" // 2
"clr r16 \n" // 1
"nop \n nop \n nop \n nop \n nop \n" // 5
OUT1
"; done :) \n\n\n"
"; now the final thing is to wait for DATA become high again (should be immediately anyway) \n"
"send_final_loop: \n"
"inc r16 \n"
"breq timeout \n"
"sbis %1, 5 \n"
"rjmp send_final_loop \n\n\n"
";;;;;;;; RECEIVE PART ;;;;;;;;\n\n"
"clr r16 \n"
"recv_wait_low_initial_loop: \n"
"inc r16 \n"
"breq timeout \n"
"sbic %1, 5 \n"
"rjmp recv_wait_low_initial_loop \n" // from low to the start of counting: 6 cycles = 0.5us
"nop \n"
"nop \n"
"nop \n"
"nop \n"
"recv_loop: \n"
"recv_low_begin: \n"
"ldi r16, 128 \n" // 1
"recv_low_loop: \n"
"inc r16 \n" // 1
"breq timeout \n" // 1 if no timeout
"sbis %1, 5 \n" // 1 // von high auf dec: 6
"rjmp recv_low_loop \n\n" // 2 if executed, 1 if skipped.
"nop \n" // to account for the rjmp recv_loop below.
"nop \n"
"nop \n"
"nop \n"
"recv_high_begin: \n"
"nop \n" // to account for the ldi in recv_low_begin.
"recv_high_loop: \n"
"dec r16 \n" // 1
"breq timeout \n" // 1 if no timeout
"sbic %1, 5 \n" // 1 // von low auf inc: 6
"rjmp recv_high_loop \n\n" // 2 if executed, 1 if skipped
"st z+, r16 \n" // 2
"rjmp recv_loop \n\n" // 2
"timeout: \n"
: "+z" ((unsigned char volatile*) buf_ptr)
: "I" (_SFR_IO_ADDR(PINC)),
"I" (_SFR_IO_ADDR(DDRC)),
"w" (len)
: "r16", "memory"
);
return buf_ptr-buffer;
// a value of >=128 means "0", <127 means "1" bit.
}
int main (void)
{
DDRC=0x00;
PORTC=0x00;
DDRB=0xFF;
DDRD=0x00;
PORTB=0x55;
int temp=0;
int n_received;
while(1)
{
temp++;
if (!(PIND & 0x08))
{
//PORTB=~(1 << ((temp>>9)%6));
PORTB=~temp;
}
else if (!(PIND & 0x20))
{
PORTB=~n_received>>3;
}
else if (!(PIND & 0x40))
{
PORTB=~0x00;
}
else
{
//PORTB=~buffer[4];
char tmp=0;
for (int i=0;i<8;i++)
tmp|= ( (buffer[i]&0x80)?0:(1<<i) );
PORTB=~tmp;
}
_delay_ms(1);
char foo[] = { 0x40, 0x03, 0x02 };
n_received=send_recv_gc(foo, 3);
}
return 0; // never reached
}
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