[SDL] Event and serial port

[benang at cs.its.ac.id]

OIC, thanks. Then using a thread to handle the serial port is unavoidable
then. And I thought it can be done in SDL_event so that I didn't have to
use a thread. So that's one more thread to add to the program. Sigh... I
don't like threading very much. Have a bad experience with it.

> This is a two part answer. First I will attempt to address working
> with a serial device. Secondly I will talk about SDL events.
>
> SDL does not provider support for serial port devices. You will have
> to use platform specific code to access the serial device -- or a
> cross-platform library that implements the platform specific code for
> serial device access on various platforms. The main point: SDL has no
> built in support for serial devices.
>
> Onto events. SDL provides reserved an event type for the programmer to
> implement his own events. Just as the event type for mouse movements
> is SDL_MOUSEMOTION, the event type for this programmer-defined
> SDL_event is SDL_USEREVENT.
>
> The SDL_UserEvent structure is structured to give you your own
> tier-two event code. Instead of being named "type" it is named "code."
> It also gives you two pointers which you can point at arbitrary
> objects containing arbitrary amounts of data, or cast / union and use
> as scalar data types (which you probably want if you're just receiving
> characters.) So it's pretty flexible.
>
> typedef struct{
>   Uint8 type; // must be SDL_USEREVENT i think
>   int code;
>   void *data1;
>   void *data2;
> } SDL_UserEvent;
>
> So theoretically, on many platforms you should be able to register
> your hook / callback routine that your kernel will invoke within your
> program, in between execution of your main thread (in a manner of
> speaking,) which can then allocate an SDL_UserEvent on the heap
> (malloc(),) and use SDL_PushEvent(eventPtr) into the SDL event queue.
>
> However personally I recommend against this. The SDL event queue can
> easily create a lot more overhead than should be necessary for just
> receiving input from a character stream. Also I imagine if your device
> or connection went awry and your SDL program started receiving data
> very quickly, it may slow down immensely, or fill up more quickly than
> it's emptying (spend more time in interrupts than in main execution)
> and run out of memory (that's not a fun thing to do, especially on
> Windows.)
>
> If you are not committed to C or C++, I highly recommend Python. There
> are some _really_ simple cross-platform serial I/O libraries out
> there. For SDL in Python visit Pygame.org.
>
> On 10/30/06, benang at cs.its.ac.id <benang at cs.its.ac.id> wrote:
>> Hi, first of all I'll say thank you to those who replied my last post a
>> week ago. I've been away for a week to my hometown.
>>
>> The application I'm developing uses a device that's attached to serial
>> port. The device is used as input and output. The device has a program
>> embedded in it that can send (input) and receive (output) a string and
>> it's built like a NULL modem. The input is in a form of a button. If the
>> button is pressed, it'll send a series of string continuously (until I
>> send a string to the device to stop it). And the output is in a form of
>> a
>> LED. If I send a string to it, the LED will blink. My question is, can
>> this be handled in SDL_Event?
>>
>> Thanks in advance.
>>