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#include "N64Interface.h"
#include <Arduino.h>
#include <pins_arduino.h>
#define NOP asm volatile ("nop")
#define NOP5 asm volatile ("nop\nnop\nnop\nnop\nnop\n")
#define NOP30 asm volatile ("nop\nnop\nnop\nnop\nnop\n" \
"nop\nnop\nnop\nnop\nnop\n" \
"nop\nnop\nnop\nnop\nnop\n" \
"nop\nnop\nnop\nnop\nnop\n" \
"nop\nnop\nnop\nnop\nnop\n" \
"nop\nnop\nnop\nnop\nnop\n")
// these two macros set arduino pin 2 to input or output, which with an
// external 1K pull-up resistor to the 3.3V rail, is like pulling it high or
// low. These operations translate to 1 op code, which takes 2 cycles
#define N64_PIND_HIGH DDRD &= ~pincode
#define N64_PIND_LOW DDRD |= pincode
#define N64_PIND_QUERY (PIND & pincode)
#define N64_PINB_HIGH DDRB &= ~pincode
#define N64_PINB_LOW DDRB |= pincode
#define N64_PINB_QUERY (PINB & pincode)
void N64Interface_PINB::init() {
unsigned char initialize = 0x00;
noInterrupts();
send(&initialize, 1);
int x;
for (x=0; x<64; x++) {
if (!N64_PINB_QUERY)
x = 0;
}
unsigned char command[] = {0x01};
send(command, 1);
get();
interrupts();
}
void N64Interface_PINB::send(unsigned char * buffer, char length) {
char bits;
asm volatile (";Starting outer for loop");
outer_loop:
{
asm volatile (";Starting inner for loop");
bits=8;
inner_loop:
{
asm volatile (";Setting line to low");
N64_PINB_LOW;
asm volatile (";branching");
if (*buffer >> 7) {
asm volatile (";Bit is a 1");
NOP5;
asm volatile (";Setting line to high");
N64_PINB_HIGH;
NOP30;
} else {
asm volatile (";Bit is a 0");
NOP30; NOP5; NOP;
asm volatile (";Setting line to high");
N64_PINB_HIGH;
asm volatile ("; end of conditional branch, need to wait 1us more before next bit");
}
asm volatile (";finishing inner loop body");
--bits;
if (bits != 0) {
NOP5; NOP; NOP; NOP; NOP;
asm volatile (";rotating out bits");
*buffer <<= 1;
goto inner_loop;
}
}
asm volatile (";continuing outer loop");
--length;
if (length != 0) {
++buffer;
goto outer_loop;
}
}
NOP; NOP; NOP; NOP;
N64_PINB_LOW;
NOP5; NOP5; NOP; NOP; NOP; NOP;
N64_PINB_HIGH;
}
void N64Interface_PINB::get() {
asm volatile (";Starting to listen");
unsigned char timeout;
char bitcount = 32;
char *bitbin = raw_dump;
read_loop:
timeout = 0x3f;
while (N64_PINB_QUERY) {
if (!--timeout)
return;
}
NOP30;
*bitbin = N64_PINB_QUERY;
++bitbin;
--bitcount;
if (bitcount == 0)
return;
timeout = 0x3f;
while (!N64_PINB_QUERY) {
if (!--timeout)
return;
}
goto read_loop;
}
void N64Interface_PIND::init() {
// Initialize the gamecube controller by sending it a null byte.
// This is unnecessary for a standard controller, but is required for the
// Wavebird.
unsigned char initialize = 0x00;
noInterrupts();
send(&initialize, 1);
// Stupid routine to wait for the gamecube controller to stop
// sending its response. We don't care what it is, but we
// can't start asking for status if it's still responding
int x;
for (x=0; x<64; x++) {
// make sure the line is idle for 64 iterations, should
// be plenty.
if (!N64_PIND_QUERY)
x = 0;
}
// Query for the gamecube controller's status. We do this
// to get the 0 point for the control stick.
unsigned char command[] = {0x01};
send(command, 1);
// read in data and dump it to N64_raw_dump
get();
interrupts();
}
/**
* This sends the given byte sequence to the controller
* length must be at least 1
* Oh, it destroys the buffer passed in as it writes it
*/
void N64Interface_PIND::send(unsigned char * buffer, char length) {
// Send these bytes
char bits;
// This routine is very carefully timed by examining the assembly output.
// Do not change any statements, it could throw the timings off
//
// We get 16 cycles per microsecond, which should be plenty, but we need to
// be conservative. Most assembly ops take 1 cycle, but a few take 2
//
// I use manually constructed for-loops out of gotos so I have more control
// over the outputted assembly. I can insert nops where it was impossible
// with a for loop
asm volatile (";Starting outer for loop");
outer_loop:
{
asm volatile (";Starting inner for loop");
bits=8;
inner_loop:
{
// Starting a bit, set the line low
asm volatile (";Setting line to low");
N64_PIND_LOW; // 1 op, 2 cycles
asm volatile (";branching");
if (*buffer >> 7) {
asm volatile (";Bit is a 1");
// 1 bit
// remain low for 1us, then go high for 3us
// nop block 1
NOP5;
asm volatile (";Setting line to high");
N64_PIND_HIGH;
// nop block 2
// we'll wait only 2us to sync up with both conditions
// at the bottom of the if statement
NOP30;
} else {
asm volatile (";Bit is a 0");
// 0 bit
// remain low for 3us, then go high for 1us
// nop block 3
NOP30; NOP5; NOP;
asm volatile (";Setting line to high");
N64_PIND_HIGH;
// wait for 1us
asm volatile ("; end of conditional branch, need to wait 1us more before next bit");
}
// end of the if, the line is high and needs to remain
// high for exactly 16 more cycles, regardless of the previous
// branch path
asm volatile (";finishing inner loop body");
--bits;
if (bits != 0) {
// nop block 4
// this block is why a for loop was impossible
NOP5; NOP; NOP; NOP; NOP;
// rotate bits
asm volatile (";rotating out bits");
*buffer <<= 1;
goto inner_loop;
} // fall out of inner loop
}
asm volatile (";continuing outer loop");
// In this case: the inner loop exits and the outer loop iterates,
// there are /exactly/ 16 cycles taken up by the necessary operations.
// So no nops are needed here (that was lucky!)
--length;
if (length != 0) {
++buffer;
goto outer_loop;
} // fall out of outer loop
}
// send a single stop (1) bit
// nop block 5
asm volatile ("nop\nnop\nnop\nnop\n");
N64_PIND_LOW;
// wait 1 us, 16 cycles, then raise the line
// 16-2=14
// nop block 6
NOP5; NOP5; NOP; NOP; NOP; NOP;
N64_PIND_HIGH;
}
void N64Interface_PIND::get() {
// listen for the expected 8 bytes of data back from the controller and
// blast it out to the N64_raw_dump array, one bit per byte for extra speed.
// Afterwards, call translate_raw_data() to interpret the raw data and pack
// it into the N64_status struct.
asm volatile (";Starting to listen");
unsigned char timeout;
char bitcount = 32;
char *bitbin = raw_dump;
// Again, using gotos here to make the assembly more predictable and
// optimization easier (please don't kill me)
read_loop:
timeout = 0x3f;
// wait for line to go low
while (N64_PIND_QUERY) {
if (!--timeout)
return;
}
// wait approx 2us and poll the line
NOP30;
*bitbin = N64_PIND_QUERY;
++bitbin;
--bitcount;
if (bitcount == 0)
return;
// wait for line to go high again
// it may already be high, so this should just drop through
timeout = 0x3f;
while (!N64_PIND_QUERY) {
if (!--timeout)
return;
}
goto read_loop;
}