On 2020-10-20 03:24, Ian MacArthur wrote:
> So, if you are comfortable with threads and such, that should be pretty
> straightforward. I you are not comfortable with threads... then this might
> be too complex a solution (sorry!)

	A possibly easier solution would just be to call fork() to start
	a separate process, then the child can handle sending data to the
	"Oszilloskop-App" as a realtime process, and the FLTK app can just
	kill the process ID to stop it.

	So if the FLTK app is simply a Start and Stop button for starting
	the data hose to the Oszilloskop-App, then the start button starts
	the child process to feed data to the scope, and stop kills the child
	to stop it, e.g.

#include <unistd.h>	// fork
#include <sys/types.h>	// kill()
#include <signal.h>	// kill()
..
pid_t G_child = 0;

// Your start button callback
void start_callback() {
    if ( (G_child = fork()) == 0 ) {
        // We are the child.. forever loop feed data to scope app
        while ( 1 ) {
            val = read_adc();   // whatever code reads the ADC
            write_scope(val);   // whatever code writes to the "Oszilloskop-App"
	    usleep(100);	// yield some cpu to the rest of the machine for the scope app to run
        }
    }
}

// Your stop button callback
void stop_callback() {
    if ( G_child == 0 ) return;     // child already stopped? early exit
    kill(G_child, 9);               // stop child
    if ( waitpid(G_child, NULL, 0); // wait for child to stop
,   G_child = 0;
}

	Depending on how "realtime" the data flow needs to be, you can use linux's
	realtime API to adjust the child process to be unaffected by some system
	hiccups, e.g. http://www.isy.liu.se/edu/kurs/TSEA81/lecture_linux_realtime.html

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