On Sunday 12 March 2017 13:05:58 Sebastian Kuzminsky wrote:
> On March 12, 2017 5:31:42 AM MDT, MH <mhemc2nos...@googlemail.com>
wrote:
> >Hello,
> >
> >I have a question about the behaviour of the halui bit pins and would
> >like to confirm that I understand the code correctly. I could not
> >answer
> >my question from the halui documentation.
> >
> >Do these pins activate on both a rising and a falling edge ?
> >
> >It like to use the input pin halui.program.pause to pause a running
> >program if I get a signal that might indicate that the material sheet
> >*might* have moved and the operator needs to check.
> >
> >Having a cursory look at the linuxcnc source code I suspect the halui
> >pins come from linuxcnc-dev/src/emc/usr_intf/halui.cc
> >
> >And in halui.cc these line (with lines numbers):
> >
> > 1114 static int sendProgramPause()
> > 1115 {
> > 1116 EMC_TASK_PLAN_PAUSE emc_task_plan_pause_msg;
> > 1117
> > 1118 return emcCommandSend(emc_task_plan_pause_msg);
> >
> >...
> >
> > 1544 static int check_bit_changed(bool halpin, bool &newpin)
> > 1545 {
> > 1546 if (halpin != newpin) {
> > 1547 newpin = halpin;
> > 1548 return halpin;
> > 1549 }
> > 1550 return 0;
> > 1551 }
> >
> >...
> >
> > 1654 if (check_bit_changed(new_halui_data.program_pause,
> >old_halui_data.program_pause) != 0)
> > 1655 sendProgramPause();
> >
> >That line 1654 looks to me as if both edges would trigger the msg
> >emc_task_plan_pause_msg to be send.
> >
> >Is that correct ?
>
> Almost. Look at line 1548, if the pin has switched state it turns the
> new state. So that function returns True on a positive edge, only.
>
I must be getting dense Seb, but I read that snippet around 1548 as
changing the return if they are not equal. Its not checking for a rising
edge, its checking for in-equality. Or so it looks to me.
line 1654 OTOH, would send it only on the rising edge with its !=0 test.
I think... I haven't carved any C to speak of since K&R #2 was out +
maybe 5 years.
> I notice now that the names of the variables inside the function are
> the opposite of what it seems they should be, that's confusing...
Cheers, Gene Heskett
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>
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