[ECOS] Select() issues

[ECOS] Select() issues

[Andre-John Mas]

Hi,

We have a solution working on the AdderII platform, using eCos.
One component of the application is a serial terminal, with
termios support. While putting the UI through its paces we
came across a small issue:

If we hit enter a number of times prior to the first select()
call, select() does not return when a key is pressed. I
thought that it could be to a full UART buffer, but trying

cin.ignore()

or

tcflush(fd,TCIOFLUSH)

prior to the select does not fix the issue.

My code looks something as follows:

   struct termios ts, ots; /* termios setting, old termios setting */
   int            fd = STDIN_FILENO;
   struct timeval tv;
   struct timeval *tvPtr = NULL;

   tcgetattr( fd, &ts );
   ots = ts;
   ts.c_flag &= ~(ICANON);
   tcsetattr(fd, TCSAFLUSH, &ts);

   if ( this->timeout > -1 )
   {
       tv.tv_sec = this->timeout;
       tv.tv_usec = 0;
       tvPtr = &tv;
   }

   FD_ZERO( &fds );
   FD_SET( STDIN_FILENO, &fds );

   int result = select(fd + 1, &fds, NULL, NULL, tvPtr);

Am I missing something? Any help would be appreciated.

Andre



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Re: [ECOS] Select() issues

[Andrew Lunn]

>    struct termios ts, ots; /* termios setting, old termios setting */
>    int            fd = STDIN_FILENO;

Im not an eCos termios expert, but shouldn't this be a file handle
returned by opening /dev/termios0 and not standard in?

         Andrew

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Re: [ECOS] Select() issues

[Andre-John Mas]

Does tcflush(fd,TCIOFLUSH) actually work?

I did a few tests, removing the code for modifying the terminal
attributes and find that I pass straight through select, if I
had hit a few enters before getting to the tcflush statement.

Andre

On 9-Jan-07, at 15:21 , Andre-John Mas wrote:

> Hi,
>
> We have a solution working on the AdderII platform, using eCos.
> One component of the application is a serial terminal, with
> termios support. While putting the UI through its paces we
> came across a small issue:
>
> If we hit enter a number of times prior to the first select()
> call, select() does not return when a key is pressed. I
> thought that it could be to a full UART buffer, but trying
>
> cin.ignore()
>
> or
>
> tcflush(fd,TCIOFLUSH)
>
> prior to the select does not fix the issue.
>
> My code looks something as follows:
>
>    struct termios ts, ots; /* termios setting, old termios setting */
>    int            fd = STDIN_FILENO;
>    struct timeval tv;
>    struct timeval *tvPtr = NULL;
>
>    tcgetattr( fd, &ts );
>    ots = ts;
>    ts.c_flag &= ~(ICANON);
>    tcsetattr(fd, TCSAFLUSH, &ts);
>
>    if ( this->timeout > -1 )
>    {
>        tv.tv_sec = this->timeout;
>        tv.tv_usec = 0;
>        tvPtr = &tv;
>    }
>
>    FD_ZERO( &fds );
>    FD_SET( STDIN_FILENO, &fds );
>
>    int result = select(fd + 1, &fds, NULL, NULL, tvPtr);
>
> Am I missing something? Any help would be appreciated.
>
> Andre
>
>
>
> --  
> Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ 
> ecos
> and search the list archive: http://ecos.sourceware.org/ml/ecos- 
> discuss


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Re: Re: [ECOS] Select() issues

[Andre-John Mas]

Andrew Lunn wrote:
> 
> >    struct termios ts, ots; /* termios setting, old termios setting */
> >    int            fd = STDIN_FILENO;
> 
> Im not an eCos termios expert, but shouldn't this be a file handle
> returned by opening /dev/termios0 and not standard in?
> 
>          Andrew
> 


On 10-Jan-07, at 10:32 , Andrew Lunn wrote:

   struct termios ts, ots; /* termios setting, old termios setting */
   int            fd = STDIN_FILENO;

Im not an eCos termios expert, but shouldn't this be a file handle
returned by opening /dev/termios0 and not standard in?

         Andrew

Up until this particular issue I have had no problems using "standard in".
I will look to see what effect opening /dev/termios0, but most examples
I have seen use STDIN_FILENO directly.

Changing my code slightly, I now find that I now block at cin.get().
I wondering whether I am doing something wrong when changing to canocial
mode?

char InputHandler::DoPressAnyKey()
{
    struct termios  ts, ots;
    int             c  = 0;
    int             fd = STDIN_FILENO;  
                  
    cout << "--0\n";
          
    tcflush(fd,TCIOFLUSH);    
       
    cout << "--1\n";  
          
    WaitForData();
                        
    tcgetattr(fd, &ts);     /* save tty state */
    ots = ts;               /* structure copy */
    ts.c_lflag &= ~( ICANON );
    ts.c_cc[VMIN] = 1;
    ts.c_cc[VTIME] = 0;
    tcsetattr(fd, TCSAFLUSH, &ts);
         
    cout << "--2\n";
        
    // INFO: make sure to reset terminal attributes before
    //       leaving method 
        
    if ( !IsTimedOut() ) 
    {
       cout << "--2.1\n";
       c = cin.get();
       cout << "--2.2\n";
    }
    
    cout << "--3\n";
        
    tcsetattr(fd, TCSAFLUSH, &ots); /* restore TTY state */
    
    cout << "--4\n";
        
    if ( IsTimedOut() ) 
    {
        c = 0;
    }
    
    return c;
     
}

void InputHandler::WaitForData()
{
    int             fd = STDIN_FILENO;    
    fd_set          fds;
    struct timeval  tv;
    struct timeval  *tvPtr = NULL; 
    
    cout.flush();
           
    do
    {   
        // INFO: if the time out is not zero then define the timeval and have tvPtr
        //       refer to it. if it is zero then tvPtr uses a NULL value. I things this
        //       way to avoid having to duplicate the select call and also not need to
        //       worry about memory allocation/deallocation
        
        cout << "--a\n";
        
        if ( this->timeout != 0 )
        {
            tv.tv_sec = this->timeout; 
            tv.tv_usec = 0;
            tvPtr = &tv;
        }
        else
        {
            tvPtr = NULL;
        }
        FD_ZERO( &fds );
        FD_SET( STDIN_FILENO, &fds );

        cout << "--b\n";
        
        int result = select(fd + 1, &fds, NULL, NULL, tvPtr);
        
        cout << "--c\n";
        
        if ( result == 0 )
        {
            this->timedout = true;
            break;           
        }
        else if ( result > 0 && FD_ISSET(fd,&fds) )
        {      
            break;
        }
        
        cout << "--d\n";
    }
    while ( true );
  
    cout << "--e\n";
}



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Re: Re: [ECOS] Select() issues

[Andrew Lunn]

> Up until this particular issue I have had no problems using "standard in".
> I will look to see what effect opening /dev/termios0, but most examples
> I have seen use STDIN_FILENO directly.

Please could you point me at the eCos examples that do this?

> Changing my code slightly, I now find that I now block at cin.get().
> I wondering whether I am doing something wrong when changing to canocial
> mode?
> 
> char InputHandler::DoPressAnyKey()
> {
>     struct termios  ts, ots;
>     int             c  = 0;
>     int             fd = STDIN_FILENO;  
>                   
>     cout << "--0\n";
>           
>     tcflush(fd,TCIOFLUSH);    
>        
>     cout << "--1\n";  

You are using stdout, not the file descriptor for a /dev/termios0.  I
would first determine is you are using the correct file
descriptor. When this really is wrong, nothing will work......

            Andrew

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Re: [ECOS] Select() issues

[Andre-John Mas]

On 11-Jan-07, at 13:20 , Andrew Lunn wrote:

>> Up until this particular issue I have had no problems using  
>> "standard in".
>> I will look to see what effect opening /dev/termios0, but most  
>> examples
>> I have seen use STDIN_FILENO directly.
>
> Please could you point me at the eCos examples that do this?
>
>> Changing my code slightly, I now find that I now block at cin.get().
>> I wondering whether I am doing something wrong when changing to  
>> canocial
>> mode?
>>
>> char InputHandler::DoPressAnyKey()
>> {
>>     struct termios  ts, ots;
>>     int             c  = 0;
>>     int             fd = STDIN_FILENO;
>>
>>     cout << "--0\n";
>>
>>     tcflush(fd,TCIOFLUSH);
>>
>>     cout << "--1\n";
>
> You are using stdout, not the file descriptor for a /dev/termios0.  I
> would first determine is you are using the correct file
> descriptor. When this really is wrong, nothing will work......
>
>             Andrew
>

I changed the code to read:

    int             fd = open ( "/dev/termios0", O_RDONLY) ;

in all instances, but that seems to make no difference at all. I can get
input and modify termio settings, as in the previous case, but when I
hit multiple enters (or any key for that matter) before I get to the  
code,
the select() or cin.get() don't come back.

BTW It should be noted that Termios TTY channel #0, in my ecos config  
file,
points to /dev/ser0

Andre


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