C++ program to talk to the open source libftdi driver (http://www.intra2net.com/en/developer/libftdi/) to read data from Sparkfun's USB Weather Board. Ships by default on the Rascal, http://rascalmicro.com

weather_usb.cpp

/* weather_usb.cpp

   Weather station client using libftdi

   compile:  g++ -l ftdi -o weather_usb weather_usb.cpp

   This program is distributed under the BSD license
*/

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

int main(int argc, char* argv[])
{
    int ret;
    //int f = 0;
    //char c[4096];
    struct ftdi_context ftdic;
    std::string accum;

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

    if ((ret = ftdi_usb_open(&ftdic, 0x0403, 0x6001)) < 0)
    {
        fprintf(stderr, "unable to open ftdi device: %d (%s)\n", ret, ftdi_get_error_string(&ftdic));
        return EXIT_FAILURE;
    }

    while(1) 
    {
        char c[4096];
        memset(c,0,sizeof(c));
        int n = ftdi_read_data(&ftdic, (unsigned char*)c, sizeof(c));
        accum = accum + c;

        //
        // erase anything before the last full $...*
        //
        size_t last_asterisk_pos = accum.find_last_of('*');
        if (last_asterisk_pos == std::string::npos) continue;
        size_t last_dollar_sign_with_trailing_asterisk = accum.find_last_of('$', last_asterisk_pos);
        if (last_dollar_sign_with_trailing_asterisk == std::string::npos) continue;
        accum = accum.substr(last_dollar_sign_with_trailing_asterisk);

        //
        // print out first complete $...* and remove from buffer
        //
        size_t asterisk_pos = accum.find_first_of('*');
        std::string s = accum.substr(0,asterisk_pos+1);
        printf("%s\n",s.c_str());
        accum = accum.substr(asterisk_pos+1);

        //
        // this version only prints one line of output
        //
        break;
    }

    if ((ret = ftdi_usb_close(&ftdic)) < 0)
    {
        fprintf(stderr, "unable to close ftdi device: %d (%s)\n", ret, ftdi_get_error_string(&ftdic));
        return EXIT_FAILURE;
    }

    ftdi_deinit(&ftdic);

    return EXIT_SUCCESS;
}