[Gambas-user] using events of serial ports for reading how_?

[T Lee Davidson]

On 08/13/2018 08:36 AM, PICCORO McKAY Lenz wrote:
> 2018-08-11 20:47 GMT-04:00 T Lee Davidson <t.lee.davidson at gmail.com <mailto:t.lee.davidson at gmail.com>>:
> 
>     No, there should not "always be data to read". If the printer responds there should be data to read *after a certain amount of
>     time*. You have to give the printer/driver time to respond. Your program does not.
> 
> but, does not raised automatically the event when data happened?

The _Read event should be triggered if there is data to read. But, again, your program does not allow time for the serial
communication to be effected and the _Read event raised.


>     And, you cannot rightly say that the event is never raised if you do not allow time for that to happen, which, again, your
> 
> if i removed rhe "rp" function the "Read" event never reaised

You don't give it a chance to be raised!

You create the printer object, open its port, write to the printer requesting a status report, and then *immediately* you
manually read the response. After that, for some odd reason, you read the "dataread" property twice, and then the program ends.

If you don't call the "rp" function, the program drops through the two "dataread" property reads and ends. When did you expect
the _Read event would have a chance to be raised?


> here there's no "certaing amount of time" due there's no read operatin forced manually

Not sure exactly what you mean with that statement, but it may be the very idea I am trying to impress upon you. Your manual
read subroutine gives the printer 500 milliseconds to respond. Why don't you give the Main module at least 500 milliseconds to
allow the printer to respond and raise the _Read event?

Or, why not use a semaphore that is visible to the Main module and loop until the _Read event has had an opportunity to fill the
"databuffer"?


>     Finally, if a Stream is being WATCHed, the program can (will?) hang if the Stream is not closed prior to application exit.
> 
> i not watched the stream.. and ..

You may not have specified that the SerialPort stream should be watched, but it would be logical that Gambas automatically
WATCHes a SerialPort in order to be be able to raise the _Read event. (http://gambaswiki.org/wiki/lang/open)


> the problem does not happen if i used gambas 3.1 and 3.4 do you know?

I have no idea what you mean.


___
Lee