====== SDK Script gps2serial-GNSStoGPS.are ======
<code c gps2serial-gnsstogps.are>
    /* DESC: This script sends the local GPS NMEA stream to the serial interface.
     * DESC: It checks for the correct CR/LF end of line characters and convert messages $GN to $GP 
     * Copyright (C) 2013-2021) NetModule AG, Switzerland
     */
    /* Options to configure by user*/
    SER_SPEED = (int) argv[2]; /* Serial Baud Rate 4800, 9600, 19200, 38400, 57600, 115200 */
    SER_DATABIT = 8; /*  number of data bits (5, 6, 7, 8) */
    SER_STOPBIT = 1; /*  number of stop bits (1, 2) */
    SER_PARITY = 0; /* parity (0=no parity, 1=odd parity, 2=even parity) */
    SER_FLOW = 0; /*  flow control (0=none, 1=xon/xoff, 2=hardware) */
    DEV = "SERIAL1"; /*  name of the Serial Interface */

    /* default values */
    local_ip = "127.0.0.1";
    local_port = (int) nb_config_get("gpsd.0.port");

    gpsd = -1;

    // start serial connection
    int start_serial() {
       if (nb_config_get("serial.0.status") != "2") {
          nb_syslog("serial not assinged to SDK\n");
          exit(2);
       }
       // printf("set serial attributes\n");
       if ((rc = nb_serial_setattr(DEV, SER_SPEED, SER_DATABIT, SER_STOPBIT, SER_PARITY, SER_FLOW)) != 0) {
          nb_syslog("ERROR: unable to set serial attributes (rc %d) to %s\n", rc, DEV);
          return -1;
       }
       // nb_syslog("Open serial device %s\n", DEV);
       if ((fd = nb_serial_open(DEV)) < 0) {
          nb_syslog("ERROR: can't open serial port %s\n", DEV);
          return -1;
       }
       return fd;
    }
    // restart GPS deamon
    int gpsd_restart() {
       nb_syslog("Restarting GPS daemon");

       nb_config_set("gpsd.0.status=0");
       do {
          sleep(3);
       } while (nb_config_done != 0)

       nb_config_set("gpsd.0.status=1");
       do {
          sleep(5);
       } while (nb_config_done != 0)
       return 0;
    }

    // start TCP Socket for GPS deamon loop 
    int gpsd_connect() {
       nb_syslog("Connecting to GPS daemon");

       gpsd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
       if (gpsd < 0) {
          nb_syslog("ERROR: Unable to open socket");
          exit(-1);
       }
       for (attempt = 0; attempt <= 15; attempt++) {
          sleep(15);

          if (connect(gpsd, local_ip, local_port) < 0) {
             nb_syslog("Could not connect to daemon");
             if (attempt == 12) {
                nb_syslog("Unable to connect, restarting daemon");
                gpsd_restart();
             }
          } else {
             break;
          }
       }
       nb_syslog("Connected to daemon, requesting NMEA");
       send(gpsd, "R=1\n");

       nb_syslog("Processing NMEA");

       return gpsd;
    }

    string checksum(string s) {
       pos = strchr(s, "*");

       if (is_void(pos))
          return s; /* no checksum to correct */

       cs = 0;
       chars = explode(s);
       for (i = 1; i < pos; i++) {
          /* skip $ and *XX */
          c = ord(chars[i]);
          cs ^= c;
       }
       r = sprintf("%s%02X%s", substr(s, 0, pos + 1), cs, substr(s, pos + 3));
       return r;
    }

    /* main() */

    if (argc < 2) {
       usage();
    }

    /* starting serial */
    nb_syslog("starting serial");
    if ((serial_fd = start_serial()) < 0) {
       nb_syslog("Could not start serial, exiting\n");
       exit(4);
    }

    /* process NMEA stream */
    nb_syslog("Processing NMEA data");
    while (1) {
       /* connect to gpsd */
       if (gpsd < 0) {
          gpsd = gpsd_connect(gpsd);
          if (gpsd < 0) {
             nb_syslog("ERROR: Unable to connect to daemon");
             sleep(5);
             continue;
          }
       }

       /* wait for client socket data  */
       rv = select(gpsd, 3);

       if (rv == -1) {
          nb_syslog("ERROR: select failed, re-connecting");
          close(gpsd);
          gpsd = -1;
          continue;
       } else if (rv == 0) {
          /* nothing received */
          continue;
       }

       data = recv(gpsd);
       len = strlen(data);
       /* Check for correct framing: CR+LF */
       if (len > 2) {
          if (strrchr(data, "\r") != len - 2 || strrchr(data, "\n") != len - 1) {
             nb_syslog("ERROR: NMEA framing wrong");
             close(gpsd);
             gpsd = -1;
             gpsd_restart();
             continue;
          }
       }

       if (len == 0) {
          nb_syslog("ERROR: no data, re-connecting");
          close(gpsd);
          gpsd = -1;
          continue;
       }
       /* Convert message $GN to $GP for backward compatibility */
       if (strstr(data, "$GN") == 0) {
          ;
          a_arr = explode(data);
          a_arr[2] = "P";
          data = checksum(implode(a_arr));
       }
       /* skip all messages different from GPGGA 
        * if(strstr(data,"$GPGGA")==())
        * continue;
        */
       sent = write(serial_fd, data, len);
       nb_syslog("sending Data via serial interface");
       if (write(serial_fd, data, len) != len) {
          nb_syslog("Unable to send message via Serial, data %s, len: %i\n", data, len);
       }
    }

    close(gpsd);
    close(serial_fd);
    exit(6);
</code>