File content as of revision 2:77b20c9b1933:

// TODO: work off controler 3.3v if possible

#include "mbed.h"
#include "USBHostKeyboard.h"
#include "stm32f4xx_flash.h"

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

extern "C" void my_wait_us_asm (int n);

enum STATE {NORMAL=0, A_UP, A_DOWN, A_LEFT, A_RIGHT, DPAD_UP, DPAD_DOWN, DPAD_LEFT, DPAD_RIGHT, BUTTON_START, BUTTON_B, BUTTON_A, C_UP, C_DOWN, C_LEFT, C_RIGHT, BUTTON_L, BUTTON_R, BUTTON_Z};
uint8_t state = NORMAL; //done remapping when >= 19

bool KeyboardButtonPressed = false;
void LoadControls();
void SaveControls();

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;

struct __attribute__((packed)) KeyboardControls
{
    uint8_t KEYBOARD_a;
    uint8_t KEYBOARD_b;
    uint8_t KEYBOARD_z;
    uint8_t KEYBOARD_start;
    
    uint8_t KEYBOARD_d_up;
    uint8_t KEYBOARD_d_down;
    uint8_t KEYBOARD_d_left;
    uint8_t KEYBOARD_d_right;
    
    uint8_t KEYBOARD_l;
    uint8_t KEYBOARD_r;
    uint8_t KEYBOARD_c_up;
    uint8_t KEYBOARD_c_down;
    
    uint8_t KEYBOARD_c_left;
    uint8_t KEYBOARD_c_right;
    uint8_t KEYBOARD_a_up;
    uint8_t KEYBOARD_a_down;
    
    uint8_t KEYBOARD_a_left;
    uint8_t KEYBOARD_a_right;
    
    KeyboardControls()
    {
        LoadDefault();
    }
    
    void LoadDefault()
    {
        KEYBOARD_a =         0x0E;
        KEYBOARD_b =         0x0D;
        KEYBOARD_z =         0x0F;
        KEYBOARD_start =     0x0B;
        KEYBOARD_d_up =      0x1D;
        KEYBOARD_d_down =    0x1B;
        KEYBOARD_d_left =    0x06;
        KEYBOARD_d_right =   0x19;
        KEYBOARD_l =         0x1A;
        KEYBOARD_r =         0x12;
        KEYBOARD_c_up =      0x17;
        KEYBOARD_c_down =    0x1C;
        KEYBOARD_c_left =    0x18;
        KEYBOARD_c_right =   0x0C;
        KEYBOARD_a_up =      0x08;
        KEYBOARD_a_down =    0x07;
        KEYBOARD_a_left =    0x16;
        KEYBOARD_a_right =   0x09;
    }
    
    void LoadBlank()
    {
        KEYBOARD_a =         0x00;
        KEYBOARD_b =         0x00;
        KEYBOARD_z =         0x00;
        KEYBOARD_start =     0x00;
        KEYBOARD_d_up =      0x00;
        KEYBOARD_d_down =    0x00;
        KEYBOARD_d_left =    0x00;
        KEYBOARD_d_right =   0x00;
        KEYBOARD_l =         0x00;
        KEYBOARD_r =         0x00;
        KEYBOARD_c_up =      0x00;
        KEYBOARD_c_down =    0x00;
        KEYBOARD_c_left =    0x00;
        KEYBOARD_c_right =   0x00;
        KEYBOARD_a_up =      0x00;
        KEYBOARD_a_down =    0x00;
        KEYBOARD_a_left =    0x00;
        KEYBOARD_a_right =   0x00;
    }
};

KeyboardControls kc;

const int SAVE_ADDR = 0x0800C000; // sector 3
KeyboardControls* saveData = (KeyboardControls*)SAVE_ADDR; 

// 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();
}

char reverse(char b) 
{
   b = (b & 0xF0) >> 4 | (b & 0x0F) << 4;
   b = (b & 0xCC) >> 2 | (b & 0x33) << 2;
   b = (b & 0xAA) >> 1 | (b & 0x55) << 1;
   return b;
}

void ChangeButtonMapping(uint8_t bt)
{
    // analog settings must be hardcoded, cannot change on the fly
    if(state == A_UP) // state = 1 --> analog up
    {
        kc.KEYBOARD_a_up = bt;
    }
    else if(state == A_DOWN) // state = 2 --> analog up
    {
        kc.KEYBOARD_a_down = bt;
    }
    else if(state == A_LEFT) // state = 3 --> analog up
    {
        kc.KEYBOARD_a_left = bt;
    }
    else if(state == A_RIGHT) // state = 4 --> analog up
    {
        kc.KEYBOARD_a_right = bt;
    }
    else if(state == DPAD_UP) // state = 5 --> dpad up
    {
        kc.KEYBOARD_d_up = bt;
    }
    else if(state == DPAD_DOWN) // state = 6 --> dpad down
    {
        kc.KEYBOARD_d_down = bt;
    }
    else if(state == DPAD_LEFT) // state = 7 --> dpad left
    {
        kc.KEYBOARD_d_left = bt;
    }
    else if(state == DPAD_RIGHT) // state = 8 --> dpad right
    {
        kc.KEYBOARD_d_right = bt;
    }
    else if(state == BUTTON_START) // state = 9 --> start
    {
        kc.KEYBOARD_start = bt;
    }
    else if(state == BUTTON_B) // state = 10 --> B
    {
        kc.KEYBOARD_b = bt;
    }
    else if(state == BUTTON_A) // state = 11 --> A
    {
        kc.KEYBOARD_a = bt;
    }
    else if(state == C_UP) // state = 12 --> c up
    {
        kc.KEYBOARD_c_up = bt;
    }
    else if(state == C_DOWN) // state = 13 --> c down
    {
        kc.KEYBOARD_c_down = bt;
    }
    else if(state == C_LEFT) // state = 14 --> c left
    {
        kc.KEYBOARD_c_left = bt;
    }
    else if(state == C_RIGHT) // state = 15 --> c right
    {
        kc.KEYBOARD_c_right = bt;
    }
    else if(state == BUTTON_L) // state = 16 --> L
    {
        kc.KEYBOARD_l = bt;
    }
    else if(state == BUTTON_R) // state = 17 --> R
    {
        kc.KEYBOARD_r = bt;
    }
    else if(state == BUTTON_Z) // state = 18 --> Z
    {
        kc.KEYBOARD_z = bt;
    }
}

void AdvanceState()
{
    state++;
    if(state >= 19) // we're done mapping the controls
    {
        SaveControls(); // write directly to flash
        state = NORMAL; // back to normal controller operation
    }
}

void onKeyboardEvent(uint8_t rep[9])
{
    // the buttons all become 1 if overflow, i think.  or in short, [2] == [3]    
    if(rep[2] == rep[3] && rep[2] == 1)
        return;
    
    if(state == NORMAL)
    {
        memset(&n64_data,0,4); // clear controller state
        
        // keyboard buttons are stored in cells 2 3 4 5 6 7?  cell 0 and 1 are modifiers?  cell8 is an F?    
        for(int index = 2;index < 8;index++)
        {
            if(rep[index] == 0) // no more keys to process
            {
                break;
            }        
            if(rep[index] == kc.KEYBOARD_a)
            {
                n64_data.a = 1;
                continue;
            }
            if(rep[index] == kc.KEYBOARD_b)
            {
                n64_data.b = 1;
                continue;
            }
            if(rep[index] == kc.KEYBOARD_z)
            {
                n64_data.z = 1;
                continue;
            }
            if(rep[index] == kc.KEYBOARD_start)
            {
                n64_data.start = 1;
                continue;
            }
            if(rep[index] == kc.KEYBOARD_d_up)
            {
                n64_data.up = 1;
                continue;
            }
            if(rep[index] == kc.KEYBOARD_d_down)
            {
                n64_data.down = 1;
                continue;
            }
            if(rep[index] == kc.KEYBOARD_d_left)
            {
                n64_data.left = 1;
                continue;
            }
            if(rep[index] == kc.KEYBOARD_d_right)
            {
                n64_data.right = 1;
                continue;
            }
            if(rep[index] == kc.KEYBOARD_l)
            {
                n64_data.l = 1;
                continue;
            }
            if(rep[index] == kc.KEYBOARD_r)
            {
                n64_data.r = 1;
                continue;
            }
            if(rep[index] == kc.KEYBOARD_c_up)
            {
                n64_data.c_up = 1;
                continue;
            }
            if(rep[index] == kc.KEYBOARD_c_down)
            {
                n64_data.c_down = 1;
                continue;
            }
            if(rep[index] == kc.KEYBOARD_c_left)
            {
                n64_data.c_left = 1;
                continue;
            }
            if(rep[index] == kc.KEYBOARD_c_right)
            {
                n64_data.c_right = 1;
                continue;
            }
            // NOTE: THESE BITS MUST BE WRITTEN IN REVERSE ORDER.  HIGH BIT IS IN THE LOW POSITION
            if(rep[index] == kc.KEYBOARD_a_up)
            {
                n64_data.y_axis = 0x0A; // 80(dec) bit reversed
                continue;
            }
            if(rep[index] == kc.KEYBOARD_a_down)
            {
                n64_data.y_axis = 0x0D; // -80(dec) bit reversed
                continue;
            }
            if(rep[index] == kc.KEYBOARD_a_left)
            {
                n64_data.x_axis = 0x0D;
                continue;
            }
            if(rep[index] == kc.KEYBOARD_a_right)
            {
                n64_data.x_axis = 0x0A;
                continue;
            }
        }
    }
    else // state > 0 so we are in the process of changing controls
    {
        uint8_t b = rep[2]; // read for button presses (just take first pressed if many are pressed)
        if(b != 0) /*button was actually is pressed*/
        {
            if(KeyboardButtonPressed == false)
            {
                KeyboardButtonPressed = true;
                ChangeButtonMapping(b);
                AdvanceState();
            }
        }
        else
        {
            KeyboardButtonPressed = false;
        }
    }
}

void PrintBytes(char *ptr, int numBytes)
{
    pc.printf("[");
    for(int i=0;i < numBytes;i++)
    {
        pc.printf(" %X ",*ptr);
        ptr++;
    }
    pc.printf("]\r\n");
}

void SaveControls()
{
    FLASH_Unlock(); //unlock flash writing
    FLASH_ClearFlag(FLASH_FLAG_EOP | FLASH_FLAG_OPERR | FLASH_FLAG_WRPERR | 
                  FLASH_FLAG_PGAERR | FLASH_FLAG_PGPERR|FLASH_FLAG_PGSERR);
    FLASH_EraseSector(FLASH_Sector_3,VoltageRange_3); // 0x0800C000 - 0x0800FFFF
    
    uint32_t* data = (uint32_t*)&kc;
    
    // total size is 18 bytes
    // Note: ProgramDoubleWord requires a higher voltage
    FLASH_ProgramWord(SAVE_ADDR,*data); // write word 1 (4 bytes)
    data++;
    FLASH_ProgramWord(SAVE_ADDR+0x04,*data); // write word 2 (4 bytes)
    data++;
    FLASH_ProgramWord(SAVE_ADDR+0x08,*data); // write word 3 (4 bytes)
    data++;
    FLASH_ProgramWord(SAVE_ADDR+0x0C,*data); // write word 4 (4 bytes)
    data++;
    FLASH_ProgramHalfWord(SAVE_ADDR+0x10,*data); // write final half word (2 bytes)
        
    FLASH_Lock(); // lock it back up
}



void LoadControls()
{
    memcpy(&kc,saveData,sizeof(KeyboardControls));
    pc.printf("Controls have been loaded!\r\n");
}

int main()
{
    bool buttonPressed = false;
    
    pc.printf("\r\nNow loaded! SystemCoreClock = %d Hz\r\n", SystemCoreClock);
    LoadControls();

    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)
    {
        if(state == NORMAL)
        {
            if(!button) // user wants to change controls
            {
                if(!buttonPressed) // make sure it's a separate button press
                {
                    buttonPressed = true;
                    state++;
                    continue;
                }
            }
            else
            {
                buttonPressed = false;
            }
            
            // Set pin mode to input
            data.input();
            
            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
        }
        else
        {
            if(!button) // user wants to cancel and return to regular mode
            {
                if(!buttonPressed) // make sure it's a separate button press
                {
                    state = NORMAL;
                    buttonPressed = true;
                    continue;
                }
            }
            else
            {
                buttonPressed = false;
            }
            
            myled = !myled;
            USBHost::poll();
            wait(0.1);
            
            if(state == NORMAL) // about to return to normal operation, make sure the LED remains off
            {
                myled = false;
                KeyboardButtonPressed = false;
            }
        }
    }
}