libmodbus

WAIT_DATA()

Asked by William Sallum

Hi !

I´m porting libmodbus to a non-Linux microcontroller-based device, and I need to understand how the function WAIT_DATA() works.
Then I could port it to another language.

Could someone help me please?

thanks in advance

william

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Stéphane Raimbault
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Stéphane Raimbault (sra) said : 		#1

It's just a macro with a select (POSIX system call), a macro is used because I need to call it more than one time and I don't want a function with too many parameters.

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William Sallum (wsallum) said : 		#2

Ok Stéphane, so basically the purpose of WAIT_DATA() is check if there is data to be read from serial port or socket, setting a timeout of " tv " . The data read is stored into descriptor " mb_param->fd ".

After that, the " read " command consumes the receive buffer from " fd " and store into " p_msg ".

Am I right ?

thanks

william

Revision history for this message
Best Stéphane Raimbault (sra) said : 		#3

2010/4/14 William Sallum <email address hidden>:
> Question #107314 on libmodbus changed:
> https://answers.launchpad.net/libmodbus/+question/107314
>
>    Status: Answered => Open
>
> William Sallum is still having a problem:
> Ok Stéphane, so basically the purpose of WAIT_DATA() is check if there
> is data to be read from serial port or socket, setting a timeout of  "
> tv  " . The data read is stored into descriptor " mb_param->fd ".
>
> After that, the " read " command  consumes the receive buffer from " fd
> " and store into " p_msg ".
>
> Am I right ?
>

Yes.

PS: Take care to fetch the code from github (see link on home page).

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William Sallum (wsallum) said : 		#4

Thank you Stéphane.

PS: Ok ! (I was fetching the code from libmodbus-2.0.3).

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William Sallum (wsallum) said : 		#5

Thanks Stéphane Raimbault, that solved my question.

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Stéphane Raimbault (sra) said : 		#6

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