rfid / avrfid2.c

Trammell Hudson 318bd2a 





Trammell Hudson 3dd0f57 





Trammell Hudson 318bd2a 




Trammell Hudson 3dd0f57 



Trammell Hudson 318bd2a 
Trammell Hudson 3dd0f57 







Trammell Hudson 318bd2a 




Trammell Hudson 3dd0f57 

Trammell Hudson 318bd2a 












Trammell Hudson 3dd0f57 
Trammell Hudson 318bd2a 
























Trammell Hudson 3dd0f57 
Trammell Hudson 318bd2a 




Trammell Hudson 3dd0f57 
Trammell Hudson 318bd2a 





























Trammell Hudson 3dd0f57 
Trammell Hudson 318bd2a 



















































Trammell Hudson 3dd0f57 











Trammell Hudson 318bd2a 
Trammell Hudson 3dd0f57 
Trammell Hudson 318bd2a 





Trammell Hudson 3dd0f57 
Trammell Hudson 318bd2a 
Trammell Hudson 3dd0f57 
#include <avr/io.h>

/* Use r16 and r17 to track the state of the pins */
volatile  register  uint8_t r16 __asm__("r16"); 
volatile  register  uint8_t r17 __asm__("r17"); 

/**
 * Delay a specific number of clock cycles.
 *
 * rjmp is 2 clocks, nop is 1.
 * So do one nop if the delay is an odd value and then rjmp's for n/2.
 */
static inline void
delay(
	const uint8_t n
)
{
	if (n % 2 == 1)
		asm("nop");

	switch (n/2)
	{
	case 8: asm("rjmp .+0");
	case 7: asm("rjmp .+0");
	case 6: asm("rjmp .+0");
	case 5: asm("rjmp .+0");
	case 4: asm("rjmp .+0");
	case 3: asm("rjmp .+0");
	case 2: asm("rjmp .+0");
	case 1: asm("rjmp .+0");
	case 0: break;
	}
}


static void
__attribute__((__always_inline__))
toggle(	
	const uint8_t n
)
{
	delay(n-2);
	asm(
		"eor r16, r17\n"
		"out 0x17, r16\n"
	);
}


static void
__attribute__((__always_inline__))
baseband_0(void
	//uint8_t startloop
)
{
	//if (startloop)
		toggle(2);
	//else
		//toggle(4);

	toggle(4); // 8
	toggle(4); // 12
	toggle(4); // 16
	toggle(4); // 20
	toggle(4); // 24
	toggle(4); // 28
	toggle(4); // 32
	toggle(4); // 36
	toggle(4); // 40
	toggle(4); // 44
	toggle(4); // 48
	toggle(4); // 52
}


static void
__attribute__((__always_inline__))
baseband_1(void
	//uint8_t startloop
)
{
	//if (startloop)
		toggle(2);
	//else
		//toggle(5);

	toggle(5); // 10
	toggle(5); // 15
	toggle(5); // 20
	toggle(5); // 25
	toggle(5); // 30
	toggle(5); // 35
	toggle(5); // 40
	toggle(5); // 45
	toggle(5); // 50
}


static inline void
header(void)
{
	baseband_0();
	baseband_0();
	baseband_0();
	baseband_0();
	baseband_1();
	baseband_1();
	baseband_1();
	baseband_1();
}


static void
__attribute__((__always_inline__))
manchester_bit(
	const uint8_t x
)
{
	if (x)
	{
		baseband_1();
		baseband_0();
	} else {
		baseband_0();
		baseband_1();
	}
}

static inline void
__attribute__((__always_inline__))
manchester(
	const uint32_t x,
	const uint8_t bits
)
{
	switch(bits)
	{
	case 20: manchester_bit(x >> 20);
	case 19: manchester_bit(x >> 19);
	case 18: manchester_bit(x >> 18);
	case 17: manchester_bit(x >> 17);
	case 16: manchester_bit(x >> 16);
	case 15: manchester_bit(x >> 15);
	case 14: manchester_bit(x >> 14);
	case 13: manchester_bit(x >> 13);
	case 12: manchester_bit(x >> 12);
	case 11: manchester_bit(x >> 11);
	case 10: manchester_bit(x >> 10);
	case  9: manchester_bit(x >>  9);
	case  8: manchester_bit(x >>  8);
	case  7: manchester_bit(x >>  7);
	case  6: manchester_bit(x >>  6);
	case  5: manchester_bit(x >>  5);
	case  4: manchester_bit(x >>  4);
	case  3: manchester_bit(x >>  3);
	case  2: manchester_bit(x >>  2);
	case  1: manchester_bit(x >>  1);
	case  0: break;
	}
}


#define HID_MFG_CODE        0x01002  // Do not modify
#define HID_SITE_CODE       42
#define HID_UNIQUE_ID       23946     // May be written on the back of the card

static void
__attribute__((__noinline__))
//__attribute__((section(".fini8")))
hid_output(void)
{
	header();
	manchester(HID_MFG_CODE, 20);
	manchester(HID_SITE_CODE, 8);
	manchester(HID_UNIQUE_ID, 16);
	manchester(0, 1);
}

int
__attribute__((section(".init9")))
main(void)
{
	r16 = 0;
	r17 = 3;

	while (1)
		hid_output();
}
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