[fpc-pascal] Using built-in serial instead of synaser and the like for Linux console app?

[Michael Van Canneyt]

On Tue, 1 Sep 2020, Bo Berglund via fpc-pascal wrote:

> On Tue, 01 Sep 2020 10:22:08 +0200, Bo Berglund via fpc-pascal
> <fpc-pascal at lists.freepascal.org> wrote:
>
>> Maybe I could tie the timeout to the actual baud used? Slower speeds
>> use longer timeout etc? Timeout could be set to the time it takes to
>> transfer the number of bytes to read?
>>
>> And both arguments could be made properties of the class such that the
>> user can tweak performance a bit?
>
> I tried to do this:
>
>  TComPortReadThread=class(TThread)
>  private
>    FBuffer: TBytes;
>    FPacketSize: integer; default 10;
>    FReadTimeout: integer; default 10;
>  public
>    MustDie: boolean;
>    Owner: TFpSerialPort;
>    property ReadPacketSize: integer read FPacketSize write
> FPacketSize; //How many bytes to read in each operation
>    property ReadTimeout: integer read FReadTimeout write
> FReadTimeout;    //Max time to wait for data in thread
>  protected
>    procedure CallEvent;
>    procedure Execute; override;
>  published
>    property Terminated;
>  end;
>
> But I cannot set the default value of the two new fields FPacketSize
> and FReadTimeout, I get an error in the above code (and variations of
> the same).
> Is there no way to declare a property to have a default non-zero
> value?

You must set it on the property:

Property property ReadPacketSize: integer read FPacketSize write FPacketSize default 10;

Note that this does not actually set the property to the indicated value. It
is only a hint for the streaming system:

You must still set the default value in the constructor.

>
> Note that the thread itself has no idea what is the baudrate in use so
> it cannot calculate the proper value at the start of Execute...
> And there is no Create method either that I can use.

The constructor can always be overridden.

Michael.