Re: [gpsd-dev] Example code for libgps using shared memory

[David Huichen Dai]

Hi Gary,

Please ignore my previous email. It turns out that the latest version of gpsd contains both the daemon and the libgps, so I shouldn't install another libgps using the apt-get install command.

And I would like to report that after installation, the path to the library libgps.so.23 (/usr/local/lib) will not be added to the environmental variable automatically. 

After I add the path to LD_LIBRARY_PATH manually, the code using the shared memory method works properly.

Thank you so much for your help.

David

+++++++++++++++++++++++++++++++++ 

On Thu, Nov 9, 2017 at 1:27 PM, David Huichen Dai <address@hidden> wrote:

Hi Gary,

Thanks for your reply.

I uninstalled the gpsd (3.9) from my computer, which were installed by the sudo apt-get install commands.

Next based on your instructions, I cloned the source code using:

git clone https://git.savannah.nongnu.org/git/gpsd.git

and install using:

scons && scons check && sudo scons udev-install

Now I have the latest version of gpsd

address@hidden:~$ gpsd -V

gpsd: 3.18~dev (revision release-3.17-21-g7e7c547)

Then I ran xgps, and it got a good fix.

I also captured packets on the loopback interface and found that xgps uses the socket to talk to gpsd because there were traffic to or from port 2947.

Afterwards, I compiled and ran the code you sent to me in your last email.

However, I got nothing at the terminal, not even the "no GPS data available".

I uninstalled and re-installed the gpslib-dev (with sudo apt-get commands), still the same result.

One more strange thing is, when I ran the code using socket to talk to gpsd, 

I could not get the coordinates either.

What do you think is the possible problem?

Thanks a lot~

David

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On Thu, Nov 9, 2017 at 2:46 AM, Gary E. Miller <address@hidden> wrote:

Yo David!

On Wed, 8 Nov 2017 21:12:46 +0800
David Huichen Dai <address@hidden> wrote:

> Below is my code. However, I am unable to obtain the coordinates. How
> do I achieve this?

Your code was corrupted by your emai client.  I cleaned it up, fixed
a warning.  Works for me.  See attached.


My gpsd is built locally from git head.

My gpsd is started this way: gpsd -n /dev/ttyS0

cgps says I have a good fix.

Here is how I built and ran it.  Sorry for the run together:

# gcc test.c -lgps -o test
# ./test
latitude: 44.068688, longitude: -121.314101, speed: 0.392819,
timestamp: 1510166605.000000

^C

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

            Veritas liberabit vos. -- Quid est veritas?
    "If you can’t measure it, you can’t improve it." - Lord Kelvin

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==================================================
David Huichen Dai, PhD

Research assistant
Lab of Broadband Network Switching Technology and Communication
Dept. of Computer Science and Technology
Tsinghua University, Beijing, P.R. China, 100084
Tel: 86-010-6277-3441
Email: address@hidden; address@hidden
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==================================================
David Huichen Dai, PhD

Research assistant
Lab of Broadband Network Switching Technology and Communication
Dept. of Computer Science and Technology
Tsinghua University, Beijing, P.R. China, 100084
Tel: 86-010-6277-3441
Email: address@hidden; address@hidden
==================================================