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New gcn64 transmit function (faster, lighter)

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This commit is contained in:
Raphael Assenat 2015-10-26 23:35:06 -04:00
parent df629e9d28
commit d36b9ee4ee
1 changed files with 114 additions and 1 deletions
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115
gcn64_protocol.c
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@ -109,6 +109,7 @@ void gcn64_protocol_getBytes(int offset, int n_bytes, unsigned char *dstbuf)
#define TIMING_OFFSET 100 // gives about 12uS. Twice the expected maximum bit period.
#endif
#if 1
static unsigned int gcn64_receive()
{
register unsigned int count=0;
@ -179,7 +180,119 @@ static unsigned int gcn64_receive()
return count;
}
#endif
static void gcn64_sendBytes(unsigned char *data, unsigned char n_bytes)
{
// the value of the gpio is pre-configured to low. We simulate
// an open drain output by toggling the direction.
#define PULL_DATA " sbi %0, "GCN64_BIT_NUM_S"\n"
#define RELEASE_DATA " cbi %0, "GCN64_BIT_NUM_S"\n"
asm volatile(
"mov r23, %2 \n"
"tst r23 \n"
"breq done_send \n"
"send_next_byte: \n"
"; Check if this is the last byte. \n"
"tst r23 \n"
"breq send_stop \n"
"dec r23 \n"
"ld r16, z+ \n"
"ldi r17, 0x80 ; mask \n"
"send_next_bit: \n"
"mov r19, r16 \n"
"and r19, r17 \n"
"brne send1 \n"
"nop \n"
"send0: \n"
PULL_DATA
// "sbi IO_DDRD, DATA_BIT ; Pull bus to 0 \n"
"ldi r20, 15 \n"
"lp_send0_3us: \n"
"dec r20 \n"
"brne lp_send0_3us \n"
"nop \n"
RELEASE_DATA
// "cbi IO_DDRD, DATA_BIT ; Release bus to 1 \n"
"lsr r17 \n"
"breq send_next_byte \n"
"nop \n"
"nop \n"
"nop \n"
"nop \n"
"nop \n"
"nop \n"
"rjmp send_next_bit \n"
"send1: \n"
PULL_DATA
// "sbi IO_DDRD, DATA_BIT ; Pull bus to 0 \n"
"ldi r20, 4 \n"
"lp_send1_1us: \n"
"dec r20 \n"
"brne lp_send1_1us \n"
"nop \n"
"nop \n"
RELEASE_DATA
// "cbi IO_DDRD, DATA_BIT ; Release bus to 1 \n"
"ldi r20, 10 \n"
"lp_send1_3us: \n"
"dec r20 \n"
"brne lp_send1_3us \n"
"nop \n"
"nop \n"
"lsr r17 \n"
"breq send_next_byte \n"
"nop \n"
"nop \n"
"nop \n"
"nop \n"
"nop \n"
"nop \n"
"rjmp send_next_bit \n"
"send_stop: \n"
"nop \n"
"nop \n"
"nop \n"
"nop \n"
"nop \n"
"nop \n"
"nop \n"
"nop \n"
" ; STOP BIT \n"
PULL_DATA
//" sbi IO_DDRD, DATA_BIT ; Pull low for stop bit \n"
" ldi r20, 4 \n"
"stbdly0: \n"
" dec r20 \n"
" brne stbdly0 \n"
" nop \n"
RELEASE_DATA
//" cbi IO_DDRD, DATA_BIT ; Release \n"
"done_send: \n"
:
: "I" (_SFR_IO_ADDR(GCN64_DATA_DDR)), // %0
"z" ((unsigned char volatile *)gcn64_workbuf), // %1 (Z)
"r" (n_bytes) // %2
: "r19","r16","r17","r20","r23" );
}
#if 0
static void gcn64_sendBytes(unsigned char *data, unsigned char n_bytes)
{
unsigned int bits;
@ -289,7 +402,7 @@ static void gcn64_sendBytes(unsigned char *data, unsigned char n_bytes)
"I" (_SFR_IO_ADDR(GCN64_DATA_PIN)) // %3
: "r16", "r17");
}
#endif
/* \brief Decode the received length of low/high states to byte-per-bit format
*