ftdi_testlogic.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <ftdi.h>
#include <assert.h>
#include <math.h>

/*
 * Input: RxD
 * OUT0: CTS
 * OUT1: DTR
 * OUT2: DSR
 * OUT3: DCD
 */

static void print_help_and_exit()
{
   fprintf(stderr, "Usage: ftdi_testlogic <bits_count>\n");
   exit(-1);
}

static void print_binary(int arg, int bits_count)
{
   int i;
   for(i = bits_count-1; i >= 0; i--)
   {
      printf("%d", (arg & (1 << i)) >> i);
   }
}

int main(int argc, char **argv)
{
   if(argc != 2) print_help_and_exit();

   int bits_count = atoi(argv[1]);

    struct ftdi_context *ftdi = ftdi_new();
    assert(ftdi != NULL);

    ftdi_set_interface(ftdi, INTERFACE_A);
    assert(ftdi_usb_open(ftdi, 0x0403, 0x6001) >= 0);
    assert(ftdi_set_bitmode(ftdi, 0xfc, BITMODE_BITBANG) == 0);

   int i;
   char buf[2];
   for(i = 0; i < pow(2, bits_count); i++)
   {
      buf[0] = i << 3; // Bypass TXD (output in normal mode), RXD (needed for input) and RTS (not easily available on FOCA breakout)
      ftdi_write_data(ftdi, buf, 1);
      usleep(10000);
      ftdi_read_pins(ftdi, buf);

      print_binary(i, bits_count);
      printf(" => %d\n", (buf[0] & 2) >> 1);
   }
}