Re: Change from 3.23 to 3.24 - program doesn't work?

[Gary E. Miller]

Yo David!

I can't see how that ever worked.  Your program does not check
if the receiver JSON has the data you are trying to read.

Take a look at example.c for ideas on what is missing.

On Mon, 20 Jun 2022 06:26:46 +0100
David Taylor <gm8arv@yahoo.co.uk> wrote:

> I have a program which works under 3.23 but appears to run but not
> read gps data under 3.24.  The part I am uncertain about is:
> 
>      status = gps_open (GPSD_SHARED_MEMORY, DEFAULT_GPSD_PORT,
> &gpsdata);
> 
>    #if GPSD_API_MAJOR_VERSION >= 7
>      if (gps_read (&gpsdata, NULL, 0) == -1) {
>    #else
>      if (gps_read (&gpsdata) == -1) {
>    #endif
>      } else {
> 
>        used  = gpsdata.satellites_used;
>        visible = gpsdata.satellites_visible;
>        int i; double snr_total=0;
>        for(i=0; i<=visible; i++) {
>            if (gpsdata.skyview[i].used > 0 && gpsdata.skyview[i].ss >
> 1) { snr_total+=gpsdata.skyview[i].ss;
>            }
>        }
>        gps_close (&gpsdata);
> 
> I am uncertain whether any changes would affect this code.
> 
> This is a fresh install of 3.24, compiled from source, on a fresh
> install of the Raspberry Pi OS.  cgps works correctly.  gpsd started
> manually shows as running.  No attempt to use systemd - yet.
> 
> Versions:
> 
> Linux RasPi-22 5.15.32-v7l+ #1538 SMP Thu Mar 31 19:39:41 BST 2022
> armv7l GNU/Linux
> 
> cgps: 3.24.1~dev (revision release-3.24-138-g5a53fe309)
> 
> 
> The full program below in case it helps....
> 
> ____________________________________
> /* Copyright (c) 2018-2021 David Taylor <gpsd@david.taylor.name>
> 
> Permission to use, copy, modify, and distribute this software for
> any purpose without fee is hereby granted, provided that the above
> copyright notice and this permission notice appear in all copies.
> 
> The user of the software is responsible for ensuring the accuracy
> of any data produced by the software.
> 
> This software may not be used in safety-critical
> or life-critical systems. */
> 
> #include <gps.h>
> #include <stdio.h>
> #include <string.h>
> 
> int main (int argc, char **argv) {
>    int status, used, visible;
>    struct gps_data_t gpsdata;
> 
>    #define OID_VISIBLE ".1.3.6.1.2.1.25.1.31"
>    #define OID_USED ".1.3.6.1.2.1.25.1.32"
>    #define OID_SNR_AVG ".1.3.6.1.2.1.25.1.33"
> 
>    if ((argc > 2) && (strcmp ("-g", argv[1]) == 0))
>    {
>      status = gps_open (GPSD_SHARED_MEMORY, DEFAULT_GPSD_PORT,
> &gpsdata);
> 
>    #if GPSD_API_MAJOR_VERSION >= 7
>      if (gps_read (&gpsdata, NULL, 0) == -1) {
>    #else
>      if (gps_read (&gpsdata) == -1) {
>    #endif
>      } else {
> 
>        used  = gpsdata.satellites_used;
>        visible = gpsdata.satellites_visible;
>        int i; double snr_total=0;
>        for(i=0; i<=visible; i++) {
>            if (gpsdata.skyview[i].used > 0 && gpsdata.skyview[i].ss >
> 1) { snr_total+=gpsdata.skyview[i].ss;
>            }
>        }
>        gps_close (&gpsdata);
>        double snr_avg = 0.0;
>        if (used > 0) {
>            snr_avg = snr_total / used;
>        }
>        if (strcmp (OID_VISIBLE, argv[2]) == 0) {
>          printf (OID_VISIBLE);
>          printf ("\n");
>          printf ("gauge\n");
>          printf ("%d\n", visible);
>        }
>        if (strcmp (OID_USED, argv[2]) == 0) {
>          printf (OID_USED);
>          printf ("\n");
>          printf ("gauge\n");
>          printf ("%d\n", used);
>        }
>        if (strcmp (OID_SNR_AVG, argv[2]) == 0) {
>          printf (OID_SNR_AVG);
>          printf ("\n");
>          printf ("gauge\n");
>          printf ("%lf\n", snr_avg);
>        }
>      }
>    }
>    return 0;
> }
> ____________________________________
> 
> Thanks,
> David




RGDS
GARY
---------------------------------------------------------------------------
Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
        gem@rellim.com  Tel:+1 541 382 8588

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    "If you can't measure it, you can't improve it." - Lord Kelvin

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