[Lazarus] SdpoSerial Tx and Rx buffers?

[Bo Berglund]

On Wed, 16 Feb 2011 10:53:32 +0100, Michael Schnell
<mschnell at lumino.de> wrote:

>On 02/15/2011 01:49 AM, Paulo Costa wrote:
>>
>> The SdpoSerial component creates a thread to listen and generates an 
>> event when bytes are received. So reading can be non-blocking.
>> The write methods are direct calls to the Synaser ones and they are 
>> blocking.
>>
>So I feel that SdpoSerial needs a buffer to hold the data read from the 
>interface until the main thread is inclined to bother. The size of this 
>buffer should somehow be configurable.
>

In my application I use an object that encapsulates the communication
with the instrument. I create an SdpoSerial object to do the actual
serial comm, but I also had to create a TCommBuffer class to handle
the data *from* the RS232 receive. So in the receive event of the
SdpoSerial I just dump incoming characters into this TCommBuffer
object, which keeps track of write and read indices.

The data are stuffed into a dynamic byte array, which is enlarged on
demand (but in large chunks so the overhead of expansion will not be
noticed).
I did this for receive in order to handle the "strange" protocol used
by the instrumentation.

Maybe I should expand this and use the same for transmit also, such
that the main application merely adds data to the buffer and a thread
sends the data onwards into the blocking WriteData method?
That way I can monitor the difference of the read and write indices as
a "remaining to be sent" value in a wait loop in my main application.

I might even let the thread create the SdpoSerial object so it is only
touched by the thread itself...
But I don't know what would happen because the SdpoSerial object has
internal threads of its own, I believe.

-- 

Bo Berglund
Developer in Sweden