GPSD Service: open SHM data only after cgps start

[Hans Kurscheidt]

Hi@All,

I'm Hans, German Engineer, retired, living in France. This is my 1st post, here.

Running GPSD 3.16 on an SunxI H2+ OrangePi-Zero under Debian Jessie. Couldn't get anything newer for this distribution.

I use a CPP thread to open and collect GPS data via the gpsd.service.

-------------------

void *gps_get(void *threadid) {
    struct gps_data_t gps_data;

    if ((gps_open(GPSD_SHARED_MEMORY, NULL, &gps_data)) == -1) {
        printf("code: %d, reason: %s\n", errno, gps_errstr(errno));
        exit(-1);
    }
    while (1) {
            if ((gps_read(&gps_data)) == -1) {
                printf("error occured reading gps data. code: %d, reason: %s\n", errno, gps_errstr(errno));
            }
            else {
                if ((gps_data.status == STATUS_FIX) && gps_data.fix.mode == MODE_3D) {               

... read data from gps_data

               }
                else {
                    printf("no GPS data available\n");
                }
            }
        sleep(1);
    }
    gps_close(&gps_data);

-------------------------

Everything works fine, as long as I start e.g. cgps before my application;( Once opened, I can close it). If I don't start cgps, the open statement in my app executes w/out error, but the subsequent gps_read fails w/ Error 88 "unknown Error" forever. It looks like the open statement does not really open the device?? It also works, when I start cgps, while my app is already running for a while. As soon as cgps runs, my app receives data too.

Any suggestions?

Best Regards

hk