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