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#include <avr/io.h>
#include <avr/delay.h>
static char buffer[300];
#define OUT0 "sbi %0, 5 \n" /* pull line to GND */
#define OUT1 "cbi %0, 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 recv_gc()
{
char* buf_ptr = buffer;
asm volatile(
"recv_wait_low_initial_loop: \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))
: "r16", "memory"
);
return buf_ptr-buffer;
// a value of >=128 means "0", <127 means "1" bit.
}
void send_gc(char* bytes, int len)
{
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 \n"
"push r30 \n\n"
"send_loop: \n"
"sbiw %2, 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
WAIT10
OUT1
"; done :) \n"
"pop r30 \n"
"pop r31 \n"
:
: "I" (_SFR_IO_ADDR(DDRC)),
"I" (_SFR_IO_ADDR(PINC)),
"w" (len),
"z" ((unsigned char volatile*) buffer)
: "r16"
);
}
int main (void)
{
DDRC=0x00;
PORTC=0x00;
DDRB=0xFF;
PORTB=0x55;
PORTB=0x55;
int temp=0;
while(1)
{
temp++;
// PORTB=~(1 << ((temp>>9)%6));
PORTB=~temp;
_delay_ms(1);
char foo[] = { 0x40, 0x03, 0x02 };
send_gc(foo, 3);
}
return 0; // never reached
}
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