Our request is gone before the application notices

KaiBell0628 · 5 May 2025, 12:52 UTC

Closed
KA
KaiBell0628
FR10 inspection request gets missed between polls. PLC pulses it; application sometimes clears it too. Who owns this bit? Ordinary job signals, separate safety controls.

16 replies

VI
VictorBell0620
Replying to KaiBell0628

Those two writers need sorting out first. Get both owners to draw who sets and clears each signal.

2 points
KA
KaiBell0628
Replying to VictorBell0620

Both owners say the other one clears it. Helpful.

5 points
VI
VictorBell0620
Replying to KaiBell0628

Bring the code to the meeting.

10 points
MI
MiaChan1079
Replying to KaiBell0628

And take one captured missed request with you. It gives the discussion a real sequence to explain. Otherwise you can spend an afternoon agreeing how a handshake ought to work while leaving the existing one untouched.

23 points
VI
VictorBell0620
Replying to MiaChan1079

Yes. Show them that occurrence.

10 points
KA
KaiBell0628
Replying to MiaChan1079

Trace found. PLC clears on its timer; app clears after acknowledgement. Two writers confirmed.

7 points
VI
VictorBell0620
Replying to KaiBell0628

Now agree one writer per field, plus the conditions for changing it. Put the agreement beside the signal list.

7 points
AD
AdaAdams0129
Replying to KaiBell0628

Does the application distinguish a newly issued job from a request still present after reconnect? Holding the request will help it see the value, but the job identity may still need attention.

3 points
KA
KaiBell0628
Replying to AdaAdams0129

No. It calls every first high reading a new job.

7 points
MI
MiaChan1079
Replying to KaiBell0628

That needs a recovery rule too. The operator should not have to infer whether work was accepted before the connection went away. A retained job reference and a visible unresolved state are possibilities for the interface review.

20 points
VI
VictorBennett0707
Replying to MiaChan1079

We had a class exercise that looked perfect until we closed and reopened the monitor. It immediately submitted the same job twice. The students thought they had broken the robot. They had exposed a missing case in my example. Walk through a request missed entirely, a request accepted before disconnect and a result returned while the application is away. Ask what each side knows at every step. That is a useful lesson even before any code changes, and it gives whoever supports the cell a fighting chance of explaining a stuck screen.

5 points
VI
VictorBell0620
Replying to VictorBennett0707

Ouch. Yes, add those cases.

21 points
KA
KaiBell0628
Replying to VictorBennett0707

Added to the review. Nobody is changing the polling interval as the whole fix now.

17 points
AD
AdaAdams0129
Replying to KaiBell0628

Who will own the remaining unresolved-job decision during a shift? The interface can display uncertainty correctly and still leave production waiting if no one is assigned to handle it.

18 points
KA
KaiBell0628
Replying to AdaAdams0129

Shift lead, with controls backup. Draft agreed; still needs the joint tests.

2 points
VI
VictorBell0620
Replying to KaiBell0628

Put those names on the handover. Otherwise it's back to calling whoever wrote the first version.

21 points

Discussion closed

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