#4 problem with modem status signals

[Gunter Heuckeroth]

Hello,
I have a strange behavior when using com0com port pair, setting modem status lines via EscapeCommFunction() and reading status via GetCommModemStatus() (standard "pin connection" is set for modem pair):

DTR not set:
CTS follows RTS.

DTR set
DCD set, DSR and CTS off, regardless of state of RTS

RTS set, toggling DTR:
RTS and DTR on -> DCD on (rest off)
DTR off, RTS on -> CTS on (rest off)

Did I do something wrong or is this failure reproducable?

best regards,
Gunter Heuckeroth

[Vyacheslav Frolov]

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Did you test return value of EscapeCommFunction() for error?

[Gunter Heuckeroth]

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Yes.

I wrote a small delphi program to test this. Should I attach program (and source)?

[Vyacheslav Frolov]

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Yes, attach program and source.

[Gunter Heuckeroth]

exe of test program

[Gunter Heuckeroth]

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attached exe of test program
File Added: test_bin.zip

[Gunter Heuckeroth]

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attached source
File Added: test_src.zip

[Gunter Heuckeroth]

delphi sourcee of test program

[Vyacheslav Frolov]

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rbDSR: TRadioButton;
...
rbCTS: TRadioButton;
rbDCD: TRadioButton;
...
rbCTS.Checked := (ldw_Stat and $10) <> 0;
rbDSR.Checked := (ldw_Stat and $20) <> 0;
rbDCD.Checked := (ldw_Stat and $80) <> 0;

Only one radio button can be in the checked state at the moment.
You always see the last one. So if DCD is in the checked state
then DSR and CTS are in not checked state.

[Gunter Heuckeroth]

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Hello Vyacheslav,

thanks for this advise.
Working for such a long time with delphi, and then trapped this way is bitter....
I've packed each radiobutton in a separate panel, and now it works as expected.

Gunter