// Access from ARM Running Linux

#define BCM2708_PERI_BASE        0x20000000
#define GPIO_BASE                (BCM2708_PERI_BASE + 0x200000) /* GPIO controller */


#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <dirent.h>
#include <math.h>
#include <fcntl.h>
#include <assert.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>

#include <unistd.h>

#define PAGE_SIZE (4*1024)
#define BLOCK_SIZE (4*1024)

int  mem_fd;
char *gpio_mem, *gpio_map;
char *spi0_mem, *spi0_map;


// I/O access
volatile unsigned *gpio;
volatile unsigned *allof7e;

// GPIO setup macros. Always use INP_GPIO(x) before using OUT_GPIO(x) or SET_GPIO_ALT(x,y)
#define INP_GPIO(g) *(gpio+((g)/10)) &= ~(7<<(((g)%10)*3))
#define OUT_GPIO(g) *(gpio+((g)/10)) |=  (1<<(((g)%10)*3))
#define SET_GPIO_ALT(g,a) *(gpio+(((g)/10))) |= (((a)<=3?(a)+4:(a)==4?3:2)<<(((g)%10)*3))

#define GPIO_SET *(gpio+7)  // sets   bits which are 1 ignores bits which are 0
#define GPIO_CLR *(gpio+10) // clears bits which are 1 ignores bits which are 0
#define GPIO_GET *(gpio+13)  // sets   bits which are 1 ignores bits which are 0

#define ACCESS(base) *(volatile int*)((int)allof7e+base-0x7e000000)
#define SETBIT(base, bit) ACCESS(base) |= 1<<bit
#define CLRBIT(base, bit) ACCESS(base) &= ~(1<<bit)

void setup_io();


#define CM_GP0CTL (0x7e101070)
#define GPFSEL0 (0x7E200000)
#define CM_GP0DIV (0x7e101074)
#define DMABASE (0x7E007000)

struct GPCTL {
    char SRC         : 4;
    char ENAB        : 1;
    char KILL        : 1;
    char             : 1;
    char BUSY        : 1;
    char FLIP        : 1;
    char MASH        : 2;
    unsigned int     : 13;
    char PASSWD      : 8;
};

void setup_fm()
{

    allof7e = (unsigned *)mmap(
                  NULL,
                  0x01000000,  //len
                  PROT_READ|PROT_WRITE,
                  MAP_SHARED,
                  mem_fd,
                  0x20000000  //base
              );

    if ((int)allof7e==-1) exit(-1);

    SETBIT(GPFSEL0 , 14);
    CLRBIT(GPFSEL0 , 13);
    CLRBIT(GPFSEL0 , 12);


    struct GPCTL setupword = {6/*SRC*/, 1, 0, 0, 0, 1,0x5a};

    ACCESS(CM_GP0CTL) = *((int*)&setupword);


}

void delay( int i)
{
    for(volatile unsigned int j = 1.25*(1<<i); j; j--);
}

void modulate(int m, double filteredFreq)
{
    ACCESS(CM_GP0DIV) = (0x5a << 24) + filteredFreq + m;
    //ACCESS(CM_GP0DIV) = (0x5a << 24) + 0x5000 + m;
    //
}


void playWav(char* filename, double freq)
{
    int fp = open(filename, 'r');
    int sz = lseek(fp, 0L, SEEK_END);
    lseek(fp, 0L, SEEK_SET);

    short* data = (short*)malloc(sz);
    read(fp, data, sz);
    unsigned int rnd=1;

    for (int j=22; j<sz/2; j++){ //while (read(fp, &data, 2)) {
        float dval = (float)(data[j])/65536.0*25.0;
        int intval = (int)(floor(dval));
        float frac = dval - (float)intval;
        unsigned int fracval = (unsigned int)(frac*((float)(1<<16))*((float)(1<<16)));

        for (int i=0; i<270; i++) {
          rnd = (rnd >> 1) ^ (-(rnd & 1u) & 0xD0000001u);
          modulate( intval + (fracval>rnd?1:0),freq);
        }
    }

}

//the plan is:
//use PWM to trigger DMA transfer

struct CB {
    unsigned int TI;
    unsigned int SOURCE_AD;
    unsigned int DEST_AD;
    unsigned int TXFR_LEN;
    unsigned int STRIDE;
    unsigned int NEXTCONBK;
};

struct DMAregs {
    unsigned int CS;
    unsigned int CONBLK_AD;
    unsigned int TI;
    unsigned int SOURCE_AD;
    unsigned int DEST_AD;
    unsigned int TXFR_LEN;
    unsigned int STRIDE;
    unsigned int NEXTCONBK;
    unsigned int DEBUG;
};

int main(int argc, char **argv)
{
    int g,rep;

    // Set up gpi pointer for direct register access
    setup_io();

    // Switch GPIO 7..11 to output mode

    /************************************************************************\
     * You are about to change the GPIO settings of your computer.          *
     * Mess this up and it will stop working!                               *
     * It might be a good idea to 'sync' before running this program        *
     * so at least you still have your code changes written to the SD-card! *
    \************************************************************************/

    // Set GPIO pins 7-11 to output
    for (g=7; g<=11; g++) {
        INP_GPIO(g); // must use INP_GPIO before we can use OUT_GPIO
        //OUT_GPIO(g);
    }
    //Messy code...
    double freq = 100;
    if (argc==3)
        freq = atof(argv[2]);
    if (freq < 87.5 || freq > 108.0)
      freq = 100;
    double pureFreq = round((500/freq) * 16 * 16 * 16);
    setup_fm();
    modulate(0,pureFreq);

    if (argc==3) //We must have 3 args due to the mod :P
      playWav(argv[1], pureFreq);
    else
      fprintf(stderr, "Usage:   program wavfile.wav frequency\n\nWhere wavfile is 16 bit 44.1kHz Mono\nAnd the frequency between 87.5 and 108.0\n");

    return 0;

} // main


//
// Set up a memory regions to access GPIO
//
void setup_io()
{
    /* open /dev/mem */
    if ((mem_fd = open("/dev/mem", O_RDWR|O_SYNC) ) < 0) {
        printf("can't open /dev/mem \n");
        exit (-1);
    }

    /* mmap GPIO */

    // Allocate MAP block
    if ((gpio_mem = malloc(BLOCK_SIZE + (PAGE_SIZE-1))) == NULL) {
        printf("allocation error \n");
        exit (-1);
    }

    // Make sure pointer is on 4K boundary
    if ((unsigned long)gpio_mem % PAGE_SIZE)
        gpio_mem += PAGE_SIZE - ((unsigned long)gpio_mem % PAGE_SIZE);

    // Now map it
    gpio_map = (unsigned char *)mmap(
                   gpio_mem,
                   BLOCK_SIZE,
                   PROT_READ|PROT_WRITE,
                   MAP_SHARED|MAP_FIXED,
                   mem_fd,
                   GPIO_BASE
               );

    if ((long)gpio_map < 0) {
        printf("mmap error %d\n", (int)gpio_map);
        exit (-1);
    }

    // Always use volatile pointer!
    gpio = (volatile unsigned *)gpio_map;


} // setup_io