pifm.c

// To run:
//  wget -O - http://beta.etherpad.org/p/pihackfm/export/txt 2>/dev/null | gcc -lm -std=c99 -g -xc - && ./a.out beatles.wav
// Access from ARM Running Linux


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

#define CM_GP0CTL (0x7e101070)
#define GPFSEL0 (0x7E200000)
#define CM_GP0DIV (0x7e101074)
#define CLKBASE (0x7E101000)
#define DMABASE (0x7E007000)
#define PWMBASE  (0x7e20C000) /* PWM controller */


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 getRealMemPage(void** vAddr, void** pAddr) {
    void* a = valloc(4096);
    
    ((int*)a)[0] = 1;  // use page to force allocation.
    
    mlock(a, 4096);  // lock into ram.
    
    *vAddr = a;  // yay - we know the virtual address
    
    unsigned long long frameinfo;
    
    int fp = open("/proc/self/pagemap", 'r');
    lseek(fp, ((int)a)/4096*8, SEEK_SET);
    read(fp, &frameinfo, sizeof(frameinfo));
    
    *pAddr = (void*)((int)(frameinfo*4096));
}

void freeRealMemPage(void* vAddr) {
    
    munlock(vAddr, 4096);  // unlock ram.
    
    free(vAddr);
}

void setup_fm()
{

    /* open /dev/mem */
    if ((mem_fd = open("/dev/mem", O_RDWR|O_SYNC) ) < 0) {
        printf("can't open /dev/mem \n");
        exit (-1);
    }
    
    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 modulate(int m)
{
    ACCESS(CM_GP0DIV) = (0x5a << 24) + 0x4d72 + m;
}

struct CB {
    volatile unsigned int TI;
    volatile unsigned int SOURCE_AD;
    volatile unsigned int DEST_AD;
    volatile unsigned int TXFR_LEN;
    volatile unsigned int STRIDE;
    volatile unsigned int NEXTCONBK;
    volatile unsigned int RES1;
    volatile unsigned int RES2;
    
};

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

struct PageInfo {
    void* p;  // physical address
    void* v;   // virtual address
};

struct PageInfo constPage;   
struct PageInfo instrPage;
struct PageInfo instrs[1024];


void playWav(char* filename, float samplerate)
{
    int fp= STDIN_FILENO;
    if(filename[0]!='-') 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);
    
    int bufPtr=0;
    float datanew, dataold = 0;
    short data;
    
    for (int i=0; i<22; i++)
       read(fp, &data, 2);  // read past header
    
    while (read(fp, &data, 2)) {
        float fmconstant = samplerate * 50.0e-6;  // for pre-emphisis filter.  50us time constant
        int clocksPerSample = 22500.0/samplerate*1400.0;  // for timing
        
        datanew = (float)(data)/32767;
        
        float sample = datanew + (dataold-datanew) / (1-fmconstant);  // fir of 1 + s tau
        float dval = sample*15.0;  // actual transmitted sample.  15 is bandwidth (about 75 kHz)
        
        int intval = (int)(round(dval));  // integer component
        float frac = (dval - (float)intval)/2 + 0.5;
        unsigned int fracval = frac*clocksPerSample;
         
        bufPtr++;
        while( ACCESS(DMABASE + 0x04 /* CurBlock*/) ==  (int)(instrs[bufPtr].p)) usleep(1000);
        ((struct CB*)(instrs[bufPtr].v))->SOURCE_AD = (int)constPage.p + 2048 + intval*4 - 4 ;
        
        bufPtr++;
        while( ACCESS(DMABASE + 0x04 /* CurBlock*/) ==  (int)(instrs[bufPtr].p)) usleep(1000);
        ((struct CB*)(instrs[bufPtr].v))->TXFR_LEN = clocksPerSample-fracval;
        
        bufPtr++;
        while( ACCESS(DMABASE + 0x04 /* CurBlock*/) ==  (int)(instrs[bufPtr].p)) usleep(1000);
        ((struct CB*)(instrs[bufPtr].v))->SOURCE_AD = (int)constPage.p + 2048 + intval*4+4;
        
        bufPtr=(bufPtr+1) % (1024);
        while( ACCESS(DMABASE + 0x04 /* CurBlock*/) ==  (int)(instrs[bufPtr].p)) usleep(1000);
        ((struct CB*)(instrs[bufPtr].v))->TXFR_LEN = fracval;
        
        dataold = datanew;
    }
    close(fp);
}

void unSetupDMA(){
    printf("exiting\n");
    struct DMAregs* DMA0 = (struct DMAregs*)&(ACCESS(DMABASE));
    DMA0->CS =1<<31;  // reset dma controller
    
}

void handSig() {
    exit(0);
}
void setupDMA( float centerFreq ){

  atexit(unSetupDMA);
  signal (SIGINT, handSig);
  signal (SIGTERM, handSig);
  signal (SIGHUP, handSig);
  signal (SIGQUIT, handSig);

   // allocate a few pages of ram
   getRealMemPage(&constPage.v, &constPage.p);
   
   int centerFreqDivider = (int)((500.0 / centerFreq) * (float)(1<<12) + 0.5);
   
   // make data page contents - it's essientially 1024 different commands for the
   // DMA controller to send to the clock module at the correct time.
   for (int i=0; i<1024; i++)
     ((int*)(constPage.v))[i] = (0x5a << 24) + centerFreqDivider - 512 + i;
   
   
   int instrCnt = 0;
   
   while (instrCnt<1024) {
     getRealMemPage(&instrPage.v, &instrPage.p);
     
     // make copy instructions
     struct CB* instr0= (struct CB*)instrPage.v;
     
     for (int i=0; i<4096/sizeof(struct CB); i++) {
       instrs[instrCnt].v = (void*)((int)instrPage.v + sizeof(struct CB)*i);
       instrs[instrCnt].p = (void*)((int)instrPage.p + sizeof(struct CB)*i);
       instr0->SOURCE_AD = (unsigned int)constPage.p+2048;
       instr0->DEST_AD = PWMBASE+0x18 /* FIF1 */;
       instr0->TXFR_LEN = 4;
       instr0->STRIDE = 0;
       //instr0->NEXTCONBK = (int)instrPage.p + sizeof(struct CB)*(i+1);
       instr0->TI = (1/* DREQ  */<<6) | (5 /* PWM */<<16) |  (1<<26/* no wide*/) ;
       instr0->RES1 = 0;
       instr0->RES2 = 0;
       
       if (i%2) {
         instr0->DEST_AD = CM_GP0DIV;
         instr0->STRIDE = 4;
         instr0->TI = (1<<26/* no wide*/) ;
       }
       
       if (instrCnt!=0) ((struct CB*)(instrs[instrCnt-1].v))->NEXTCONBK = (int)instrs[instrCnt].p;
       instr0++;
       instrCnt++;
     }
   }
   ((struct CB*)(instrs[1023].v))->NEXTCONBK = (int)instrs[0].p;
   
   // set up a clock for the PWM
   ACCESS(CLKBASE + 40*4 /*PWMCLK_CNTL*/) = 0x5A000026;
   usleep(1000);
   ACCESS(CLKBASE + 41*4 /*PWMCLK_DIV*/)  = 0x5A002800;
   ACCESS(CLKBASE + 40*4 /*PWMCLK_CNTL*/) = 0x5A000016;
   usleep(1000); 

   // set up pwm
   ACCESS(PWMBASE + 0x0 /* CTRL*/) = 0;
   usleep(1000);
   ACCESS(PWMBASE + 0x4 /* status*/) = -1;  // clear errors
   usleep(1000);
   ACCESS(PWMBASE + 0x0 /* CTRL*/) = -1; //(1<<13 /* Use fifo */) | (1<<10 /* repeat */) | (1<<9 /* serializer */) | (1<<8 /* enable ch */) ;
   usleep(1000);
   ACCESS(PWMBASE + 0x8 /* DMAC*/) = (1<<31 /* DMA enable */) | 0x0707;
   
   //activate dma
   struct DMAregs* DMA0 = (struct DMAregs*)&(ACCESS(DMABASE));
   DMA0->CS =1<<31;  // reset
   DMA0->CONBLK_AD=0; 
   DMA0->TI=0; 
   DMA0->CONBLK_AD = (unsigned int)(instrPage.p);
   DMA0->CS =(1<<0)|(255 <<16);  // enable bit = 0, clear end flag = 1, prio=19-16
}



int main(int argc, char **argv)
{
    
    if (argc>1) {
      setup_fm();
      setupDMA(argc>2?atof(argv[2]):103.3);
      playWav(argv[1], argc>3?atof(argv[3]):22500);
    } else
      fprintf(stderr, "Usage:   program wavfile.wav [freq] [sample rate]\n\nWhere wavfile is 16 bit 22.5kHz Mono.  Set wavfile to '-' to use stdin.\nfreq is in Mhz (default 103.3)\nsample rate of wav file in Hz\n\nPlay an empty file to transmit silence\n");
    
    return 0;

} // main