File content as of revision 1:3c21da72660d:

//TODO: save controller layout to sram
// finish and make 100% functional for keyboard players
// duplicate program and modify to work with x360

#include "mbed.h"
#include "USBHostKeyboard.h"

extern "C" void my_wait_us_asm (int n);

struct __attribute__((packed)) N64ControllerData // all bits are in the correct order
{
    unsigned int a : 1; // 1 bit wide
    unsigned int b : 1;
    unsigned int z : 1;
    unsigned int start : 1;
    unsigned int up : 1;
    unsigned int down : 1;
    unsigned int left : 1;
    unsigned int right : 1;
    
    unsigned int dummy1 : 1;
    unsigned int dummy2 : 1;
    unsigned int l :1 ;
    unsigned int r : 1;
    unsigned int c_up : 1;
    unsigned int c_down : 1;
    unsigned int c_left : 1;
    unsigned int c_right : 1;
    
    char x_axis;
    
    char y_axis;

} n64_data;

const uint8_t KEYBOARD_a =         0x0E;
const uint8_t KEYBOARD_b =         0x0D;
const uint8_t KEYBOARD_z =         0x0F;
const uint8_t KEYBOARD_start =     0x0B;
const uint8_t KEYBOARD_d_up =      0x1D;
const uint8_t KEYBOARD_d_down =    0x1B;
const uint8_t KEYBOARD_d_left =    0x06;
const uint8_t KEYBOARD_d_right =   0x19;
const uint8_t KEYBOARD_l =         0x1A;
const uint8_t KEYBOARD_r =         0x12;
const uint8_t KEYBOARD_c_up =      0x17;
const uint8_t KEYBOARD_c_down =    0x1C;
const uint8_t KEYBOARD_c_left =    0x18;
const uint8_t KEYBOARD_c_right =   0x0C; 
const uint8_t KEYBOARD_a_up =      0x08;
const uint8_t KEYBOARD_a_down =    0x07;
const uint8_t KEYBOARD_a_left =    0x16;
const uint8_t KEYBOARD_a_right =   0x09;

DigitalOut myled(LED1);
Serial pc(USBTX, USBRX); // tx, rx
DigitalInOut data(PA_8);
//DigitalIn button(PC_13); // eventually code to set controlls

// 0 is 3 microseconds low followed by 1 microsecond high
// 1 is 1 microsecond low followed by 3 microseconds high
unsigned int GetMiddleOfPulse()
{
    // wait for line to go high
    while(1)
    {
        if(data.read() == 1) break;
    }
    
    // wait for line to go low
    while(1)
    {
        if(data.read() == 0) break;
    }
    
    // now we have the falling edge
    // wait 2 microseconds to be in the middle of the pulse, and read. high --> 1.  low --> 0. 
    my_wait_us_asm(2);
    return (unsigned int) data.read();
}

// continuously read bits until at least 9 are read, confirm valid command, return without stop bit
unsigned int readCommand()
{
    unsigned int command = GetMiddleOfPulse(), bits_read = 1;
    
    while(1) // read at least 9 bits (2 bytes + stop bit)
    {
        //my_wait_us_asm(4);
        command = command << 1; // make room for the new bit
        //command += data.read(); // place the new bit into the command
        command += GetMiddleOfPulse();
        command &= 0x1FF; // remove all except the last 9 bits
        
        bits_read++;
        
        if(bits_read >= 9) // only consider when at least a whole command's length has been read
        {
            if(command == 0x3 || command == 0x1 || command == 0x1FF || command == 0x5 || command == 0x7)
            {
                // 0x3 = 0x1 + stop bit --> get controller state
                // 0x1 = 0x0 + stop bit --> who are you?
                // 0x1FF = 0xFF + stop bit --> reset signal
                // 0x5 = 0x10 + stop bit --> read
                // 0x7 = 0x11 + stop bit --> write
                command = command >> 1; // get rid of the stop bit
                return command;
            }
        }
    }
}

void write_1()
{
    data = 0;
    my_wait_us_asm(1);
    data = 1;
    my_wait_us_asm(3);
    //pc.printf("1");
}

void write_0()
{
    data = 0;
    my_wait_us_asm(3);
    data = 1;
    my_wait_us_asm(1);
    //pc.printf("0");
}


void SendStop()
{
    data = 0;
    my_wait_us_asm(1);
    data = 1;
}

// send a byte from LSB to MSB (proper serialization)
void SendByte(unsigned char b)
{
    for(int i = 0;i < 8;i++) // send all 8 bits, one at a time
    {
        if((b >> i) & 1)
        {
            write_1();
        }
        else
        {
            write_0();
        }
    }
}

void SendIdentity()
{
    // reply 0x05, 0x00, 0x02
    SendByte(0x05);
    SendByte(0x00);
    SendByte(0x02);
    SendStop();
}

void SendControllerData()
{
    unsigned long data = *(unsigned long*)&n64_data;
    unsigned int size = sizeof(data) * 8; // should be 4 bytes * 8 = 32 bits
    
    for(unsigned int i = 0;i < size;i++)
    {
        if((data >> i) & 1)
        {
            write_1();
        }
        else
        {
            write_0();
        }
    }
    
    SendStop();
}

// keyboard buttons are stored in cells 2 3 4 5 6 7?  cell 0 and 1 are modifiers?  cell8 is an F?
// the buttons all become 1 if overflow, i think.  or in short, [2] == [3]
void onKeyboardEvent(uint8_t rep[9])
{
    /*printf("Report = [");
    for(int i = 0;i < 8;i++)
    {
        printf("%X, ", rep[i]);
    }
    printf("%X]\r\n", rep[8]);*/
    
    memset(&n64_data,0,4); // clear controller state
    
    bool leaveLoop = false;
    
    for(int index = 2;index < 8;index++)
    {
        switch(rep[index]) // the key code
        {
            case 0: // no more keys to process
                leaveLoop = true;
                break;
            case KEYBOARD_a:
                n64_data.a = 1;
                break;
            case KEYBOARD_b:
                n64_data.b = 1;
                break;
            case KEYBOARD_z:
                n64_data.z = 1;
                break;
            case KEYBOARD_start:
                n64_data.start = 1;
                break;
            case KEYBOARD_d_up:
                n64_data.up = 1;
                break;
            case KEYBOARD_d_down:
                n64_data.down = 1;
                break;
            case KEYBOARD_d_left:
                n64_data.left = 1;
                break;
            case KEYBOARD_d_right:
                n64_data.right = 1;
                break;
            case KEYBOARD_l:
                n64_data.l = 1;
                break;
            case KEYBOARD_r:
                n64_data.r = 1;
                break;
            case KEYBOARD_c_up:
                n64_data.c_up = 1;
                break;
            case KEYBOARD_c_down:
                n64_data.c_down = 1;
                break;
            case KEYBOARD_c_left:
                n64_data.c_left = 1;
                break;
            case KEYBOARD_c_right:
                n64_data.c_right = 1;
                break;
            // NOTE: THESE BITS MUST BE WRITTEN IN REVERSE ORDER.  HIGH BIT IS IN THE LOW POSITION
            case KEYBOARD_a_up:
                n64_data.y_axis = 0x0A;
                break;
            case KEYBOARD_a_down:
                n64_data.y_axis = 0x0D;
                break;
            case KEYBOARD_a_left:
                n64_data.x_axis = 0x0D;
                break;
            case KEYBOARD_a_right:
                n64_data.x_axis = 0x0A;
                break;
        }
        
        if(leaveLoop) break;
    }
}

int main()
{
    pc.printf("Now loaded! SystemCoreClock = %d Hz\r\n", SystemCoreClock);
    memset(&n64_data,0,4); // start controller in the neutral state

    USBHostKeyboard kb;
    if (!kb.connect()) {
        pc.printf("Error: USB kb not found.\n");
    }
    // when connected, attach handler called on kb event
    kb.attach(onKeyboardEvent);
    
    while(1)
    {
        // Set pin mode to input
        data.input();
        
        // Read keyboard state?
        USBHost::poll();
        
        __disable_irq();    // Disable Interrupts
        // Read 64 command
        unsigned int cmd = readCommand();
        
        my_wait_us_asm(2); // wait a small amount of time before replying
 
        //-------- SEND RESPONSE
        // Set pin mode to output
        data.output();
        
        switch(cmd)
        {
            case 0x00: // identity
            case 0xFF: // reset
                SendIdentity();
                break;
            case 0x01: // poll for state
                SendControllerData();
                break;
            default:
                // we do not process the read and write commands (memory pack)
                break;
        }
        __enable_irq();    // Enable Interrupts
        //-------- DONE SENDING RESPOSE   
    }
}