#include <stdio.h>
#include <ftdi.h>

#define HC595_CT (1) // number of '595 chips

int main(int argc, char **argv)
{
    struct ftdi_context ftdic;
    int f,i, err;

    unsigned char buf[2*8*HC595_CT+1]; // latch pulse, 8*HC595_CT clock pulses

    if ((f=ftdi_init(&ftdic)) < 0)
    {
        fprintf(stderr, "ftdi_init failed\n");
        return f;
    }


    f = ftdi_usb_open(&ftdic, 0x0403, 0x6001);

    if (f < 0 && f != -5)
    {
        fprintf(stderr, "unable to open ftdi device: %d (%s)\n", f, ftdi_get_error_string(&ftdic));
        exit(-1);
    }

    printf("ftdi open succeeded: %d\n",f);

    // FTDI cable assignments:
    #define BIT_DATA (1<<0)  // 1: TXD, "data"
    #define BIT_CLOCK (1<<2) // 4: RTS, "clock"
    #define BIT_LATCH (1<<3) // 8: CTS, "latch"

    ftdi_set_bitmode(&ftdic, BIT_DATA | BIT_CLOCK | BIT_LATCH, BITMODE_BITBANG);

    // set zero
    *buf=0;
    f = ftdi_write_data(&ftdic, buf, 1);

    unsigned char *b=buf;
    unsigned char data;
    unsigned char state;

    if (argc == 2) {
      data=atof(argv[1]);
    } else {
      data=0x5a;
    }

    printf("sending data %d\n",data);

    for (i=0; i<8; i++) {
      state=(data & (128L>>i))?BIT_DATA:0;
      *b++=state;
      state |= BIT_CLOCK;
      *b++=state;
    }
    *b++=BIT_LATCH;

    f = ftdi_write_data(&ftdic, buf, (b-buf));

    ftdi_disable_bitbang(&ftdic);
    ftdi_usb_close(&ftdic);
    ftdi_deinit(&ftdic);
}