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//  mbed GBA Loader - Boot up a GameBoy Advance using Multiboot (no cart req.)
//
//  Ken Kaarvik   kkaarvik@yahoo.com
//  Nov 13, 2010
//
//  mbed            gba serial port
//   1-0V           6-0V
//  p5-mosi         3-SI
//  p6-miso         2-SO
//  p7-sck          5-SC
//  p8-input        1-3V3
//
//  p15-analogIn    0-3V3 test voltage pot
//  p16-analogIn    0-3V3 test voltage pot
//
//  note: the GBA does not power the mbed
//
//  The GBA file that you wish to load into the GBA is stored on the mbed's local file system.
//  (Just drag and drop it onto the drive where mbed is located.)
//  The GBA can be multibooted with a maximum file size of 256kB (the mbed shows up on my
//  computer as a flash drive with 2MB of memory, room for several GBA files!)
//
//  Apply power to the mbed (or reset) before turning on the GBA.
//

#include "mbed.h"

Serial pc(USBTX, USBRX);    //debug info - see raw data being transferred back and forth as GBA is booting

SPI spi(p5, p6, p7); // mosi, miso, sclk

LocalFileSystem local("local");

DigitalIn gba_present(p8);

DigitalOut myled1(LED1);    //used for my demo program (volt4.gba)
DigitalOut myled2(LED2);    //used for my demo program (volt4.gba)
DigitalOut myled3(LED3);    //used for my demo program (volt4.gba)
DigitalOut myled4(LED4);    //used for my demo program (volt4.gba)
AnalogIn voltmeter1(p15);   //used for my demo program (volt4.gba)
AnalogIn voltmeter2(p16);   //used for my demo program (volt4.gba)

unsigned long read_from_gba;
//unsigned long test_counter;

long writeSPI32bits(long write32)
{
    pc.printf("0x%08x ",write32);
    long read32 = (spi.write(write32>>16))<<16;
    read32 = (spi.write(write32))|read32;
    pc.printf("0x%08x ",read32);
    return  read32;
}

long writeSPI32bits_nodebug(long write32)
{
    long read32 = (spi.write(write32>>16))<<16;
    read32 = (spi.write(write32))|read32;
    return  read32;
}

int main() 
{
    // Setup the spi for 8 bit data, high steady state clock,
    // second edge capture, with a 100 kHz clock rate
    spi.format(16,3);
    spi.frequency(100000);

    pc.printf("\n\n\r.....GBA Multiboot Hack......\n\n\r");
    if (gba_present)
        pc.printf(".....Please turn off GBA.....\n\r");
    while(gba_present);    
    wait(0.2);    
    if(!gba_present)    
        pc.printf(".....Please turn on GBA......\n\r");
    while(!gba_present);            
    wait(0.2);
    pc.printf(".....GBA power up detected!..\n\r");        

    FILE *fp = fopen("/local/volt4.gba", "rb");             //*****change .gba file here***** 
    pc.printf(".....Opening GBA file readonly\r\n");

    fseek(fp, 0L, SEEK_END);                                //get *.gba file length
    long gba_file_length= ftell(fp);
    gba_file_length = (gba_file_length+0x0f)&0xfffffff0;    //align length to xfer to 16
    fseek(fp, 0L, SEEK_SET);
    pc.printf(".....GBA file length 0x%08x\r\n\n",gba_file_length);    
    pc.printf("MBED(mstr) GBA(slave) \r\n\n");
      
    while(read_from_gba!=0x72026202)
        {
        wait(0.01);
        read_from_gba = writeSPI32bits(0x00006202);
        pc.printf(" ;Looking for GBA\r\n");        
        }
        
    read_from_gba = writeSPI32bits(0x00006202);
    pc.printf(" ;Found GBA\r\n");

    read_from_gba = writeSPI32bits(0x00006102);
    pc.printf(" ;Recognition ok\r\n");

    int i;
    for(int Counter=0;Counter<=0x5f;Counter++)
    {
        i = getc(fp);                //Read in 16 bits of .gba file
        i = getc(fp)<<8|i;           //Read in 16 bits of .gba file

        read_from_gba =    writeSPI32bits_nodebug(0x0000ffff&i);
       // pc.printf(" ;send header a\r\n");
    }

    read_from_gba = writeSPI32bits(0x00006200);
    pc.printf(" ;Transfer of header data complete\r\n");
 
    read_from_gba = writeSPI32bits(0x00006202);
    pc.printf(" ;Exchange master/slave info again\r\n");
    
    read_from_gba = writeSPI32bits(0x000063d1);  
    pc.printf(" ;Send palette data\r\n");

    read_from_gba = writeSPI32bits(0x000063d1);  
    pc.printf(" ;Send palette data, receive 0x73hh****\r\n");

    long m    =    ((read_from_gba&0x00ff0000)>>8)+0xffff00d1;
    long hh    =    ((read_from_gba&0x00ff0000)>>16)+0xf;

    writeSPI32bits((((read_from_gba>>16)+0x0000000f)&0xff)|0x00006400);
    pc.printf(" ;Send handshake data\r\n");

    read_from_gba = writeSPI32bits((gba_file_length-0x190)/4);
    pc.printf(" ;Send length info, receive seed 0x**cc****\r\n");

    long    c    =    0x0000c387;
    long    f   =   ((((read_from_gba&0x00ff0000)>>8)+hh)+0x00)|0xffff0000;

    pc.printf("                       ;Send encrypted data (takes too long to show it all!)\r\n");

    unsigned int gba_file_location = 0xc0;
    while(gba_file_location<gba_file_length)
    {    
        long gba_data = getc(fp);               //Read in 32 bits of .gba file
        gba_data = getc(fp)<<8|gba_data;               
        gba_data = getc(fp)<<16|gba_data;        
        gba_data = getc(fp)<<24|gba_data;        
        
        long gba_data2 = gba_data;
       
        for(int bit=0;bit<32;bit++)
        {                
            if((c^gba_data)&0x01)
                c =(c>>1)^0x0000c37b;
            else
                c = c>>1;      
            gba_data = gba_data>>1;        
         }            
         m = (0x6f646573*m)+1;
         writeSPI32bits_nodebug(gba_data2^((~(0x02000000+gba_file_location))+1)^m^0x43202f2f);//This line or next two
//         writeSPI32bits(gba_data2^((~(0x02000000+gba_file_location))+1)^m^0x43202f2f);   //*****Uncomment two line to see all data being transfered*****
//         pc.printf(" ;\n\r");                                                            //*****Uncomment two line to see all data being transfered*****
         gba_file_location=gba_file_location+4;
     }

    for(int bit=0;bit<32;bit++)
    {
        if((c^f)&0x01)
            c =(c>>1)^0x0000c37b;
        else
            c = c>>1;               
        f = f>>1;
    }
        
    while (writeSPI32bits(0x00000065)!=0x00750065)
    {
        pc.printf(" ;Wait for GBA to respond with CRC\n\r");
    }
    
    pc.printf(" ;GBA ready with CRC\n\r");
    
    writeSPI32bits(0x00000066);
    
    pc.printf(" ;Let's exchange CRC!\n\r");

    writeSPI32bits(c);

    pc.printf(" ;CRC ...hope they match!\n\r");
    pc.printf("                       ;All done!\n\r\n");

    fclose(fp);         //****Done with multiboot********************************************************
    
                        //****Following is code to talk to GBA running my custom program (volt4.gba)*****
    
    while(1)   //read in analog values on p15 and p16, only use 9 bits from both, pack up and send to GBA 
    {
    read_from_gba = writeSPI32bits((voltmeter1.read_u16()>>7)|((voltmeter2.read_u16()&0xff80)<<2));
    pc.printf("\r");
    read_from_gba =(~read_from_gba)&0x3ff;
    myled1 = (read_from_gba & 0x1); //turn on led1 when "A" button on GBA is pressed
    myled2 = (read_from_gba & 0x2); //B
    myled3 = (read_from_gba & 0x4); //Select
    myled4 = (read_from_gba & 0x8); //Start
    }

}