N64 data loader configuration

// This loads 10 bytes per frame, with 10 signalling bits
// we only do bitwise operations at the beginning, and there's not too many
// (I also intentionally wrote them to be (hopefully) easier to convert to assembly)

// let the following be an array that magically contains the bytes for 3 controllers
uint8_t pad_bytes[ 12 ];

uint16_t command = 0;
uint16_t command_last = 1;

read_pad( ) {
    uint16_t temp;
    uint8_t out_bytes[ 10 ];

    // for all of the controller bytes that are full bytes, load them directly
    out_bytes[ 0 ] = pad_bytes[  0 ];
    out_bytes[ 1 ] = pad_bytes[  2 ];
    out_bytes[ 2 ] = pad_bytes[  3 ];
    out_bytes[ 3 ] = pad_bytes[  4 ];
    out_bytes[ 4 ] = pad_bytes[  6 ];
    out_bytes[ 5 ] = pad_bytes[  7 ];
    out_bytes[ 6 ] = pad_bytes[  8 ];
    out_bytes[ 7 ] = pad_bytes[ 10 ];
    out_bytes[ 8 ] = pad_bytes[ 11 ];

    // pad_bytes[ 1 ], pad_bytes[ 5 ], pad_bytes[ 9 ] only have 6 bits of useful data
    // we'll have to do some bitwise operations to compose them into bytes

    // mask off garbage bits, can skip if this isn't needed
    pad_bytes[ 1 ] &= 63;
    pad_bytes[ 5 ] &= 63;
    pad_bytes[ 9 ] &= 63;


    // --- Read extra byte ---

    // step by step bit twiddling
    temp = pad_bytes[ 5 ];  // read pad byte 5 into a register
    temp &= 3;              // mask off everything except the first two bits
    temp <<= 6;             // shift it up 6 bits, so that the first two bits are at the top of the byte
    temp |= pad_bytes[ 1 ]; // merge it with the entirety of pad byte 1

    // write it out
    out_bytes[ 9 ] = temp;

    // out_bytes now has 10 new bytes loaded into it


    // --- Read command ---

    command_last = command; // so we can detect when a command has changed (ie, started)

    // more bit level voodoo
    command = pad_bytes[ 5 ];  // store pad byte 5 in a register
    command &= 60;             // mask off the lowest two bits (which were data)
    command <<= 4;             // shift what's left up 4 bits
    command |= pad_bytes[ 9 ]; // merge all of the bits of pad byte 9 into it

    // "command" is now a 10 bit number


    // --- Execute command ---

    switch( command ) {

        default: break;
    }
}