//-------------------------------------------------------------------------
//-------------------------------------------------------------------------

//The raspberry pi wants you to not have your kernel.img file loaded
//at address 0x0000.  Using a bootloader like this it works just fine
//but to avoid having example binaries that are at 0x8000 for running
//from the sd card and a binary at 0x0000 for loading with the
//bootloader, instead the bootloader is going to default to 0x8000
//as well.
#define ARMBASE 0x8000

extern void PUT32 ( unsigned int, unsigned int );
extern void PUT16 ( unsigned int, unsigned int );
extern void PUT8 ( unsigned int, unsigned int );
extern unsigned int GET32 ( unsigned int );
extern unsigned int GETPC ( void );
extern void BRANCHTO ( unsigned int );
extern void dummy ( unsigned int );

extern void uart_init ( void );
extern unsigned int uart_lcr ( void );
extern void uart_send ( unsigned int );
extern unsigned int uart_recv ( void );
extern void hexstring ( unsigned int );
extern void hexstrings ( unsigned int );
extern void timer_init ( void );
extern unsigned int timer_tick ( void );

extern void timer_init ( void );
extern unsigned int timer_tick ( void );

//------------------------------------------------------------------------
unsigned char xstring[256];
//------------------------------------------------------------------------
int notmain ( void )
{
    unsigned int ra;
    //unsigned int rb;
    unsigned int rx;
    unsigned int addr;
    unsigned int block;
    unsigned int state;

    unsigned int crc;

    uart_init();
    hexstring(0x12345678);
    hexstring(GETPC());
    timer_init();

//SOH 0x01
//ACK 0x06
//NAK 0x15
//EOT 0x04

//block numbers start with 1

//132 byte packet
//starts with SOH
//block number byte
//255-block number
//128 bytes of data
//checksum byte (whole packet)
//a single EOT instead of SOH when done, send an ACK on it too

    block=1;
    addr=ARMBASE;
    state=0;
    crc=0;
    rx=timer_tick();
    while(1)
    {
        ra=timer_tick();
        if((ra-rx)>=4000000)
        {
            uart_send(0x15);
            rx+=4000000;
        }
        if((uart_lcr()&0x01)==0) continue;
        xstring[state]=uart_recv();
        rx=timer_tick();
        if(state==0)
        {
            if(xstring[state]==0x04)
            {
                uart_send(0x06);
                BRANCHTO(ARMBASE);
                break;
            }
        }
        switch(state)
        {
            case 0:
            {
                if(xstring[state]==0x01)
                {
                    crc=xstring[state];
                    state++;
                }
                else
                {
                    //state=0;
                    uart_send(0x15);
                }
                break;
            }
            case 1:
            {
                if(xstring[state]==block)
                {
                    crc+=xstring[state];
                    state++;
                }
                else
                {
                    state=0;
                    uart_send(0x15);
                }
                break;
            }
            case 2:
            {
                if(xstring[state]==(0xFF-xstring[state-1]))
                {
                    crc+=xstring[state];
                    state++;
                }
                else
                {
                    uart_send(0x15);
                    state=0;
                }
                break;
            }
            case 131:
            {
                crc&=0xFF;
                if(xstring[state]==crc)
                {
                    for(ra=0;ra<128;ra++)
                    {
                        PUT8(addr++,xstring[ra+3]);
                    }
                    uart_send(0x06);
                    block=(block+1)&0xFF;
                }
                else
                {
                    uart_send(0x15);
                }
                state=0;
                break;
            }
            default:
            {
                crc+=xstring[state];
                state++;
                break;
            }
        }
    }
    return(0);
}
//-------------------------------------------------------------------------
//-------------------------------------------------------------------------