Re: [rtl] Using C++ in rtlinux

[Juergen Liesmann]

Hi,

I have a newbie question.

I will write a control program for my telescope. There a three 
stepper motors. No hardware inputs at the moment. The steppers
are controlled by a 8255 chip. I must control each bit of the
two ports independent of the other bits. 

With the functions:
set bit
reset bit
flip bit
flip bit periodic

To start I have used the example from:
/usr/src/rtlinux-3.0-pre10/examples/frank
with the prepatched kernel 2.2.18.

pthread_make_periodic_np(pthread_self(), gethrtime(), msg.period );

The tasks runs and I can change msg.period with a new msg. It works
great.

Now to the problem. Sometimes i must stop the task and restart the
task later. But if I stop the task with pthread_suspend_np(pthread_self())
I can can not restart the task.

Here is a piece of the code:

...
void *thread_code(void *t)                                                      
{                                                                               
  int fifo = (int) t;                                                           
  int taskno = fifo - 1;                                                        
  struct my_msg_struct msg;                                                     

  while (1) {                                                                   
    int ret;                                                                    
    int err;                                                                    
    rtl_printf("Task %d: waiting\n", fifo - 1);
    ret = pthread_wait_np();                                                    
    rtl_printf("Task %d: wakeup\n", fifo - 1);                              
    if ((err = rtf_get (taskno + 1, &msg, sizeof(msg))) == sizeof(msg)) {       

// run periodic
      if (command == 10) {
        pthread_make_periodic_np(pthread_self(), gethrtime(), msg.period );           
      }                                                                         

// set bit                                                                      
      if (command == 13) {
        set_bit ...
        pthread_suspend_np(pthread_self());                                     
      }                                                                         

// stop
      if (command == 20) {                                                      
        pthread_suspend_np(pthread_self());                                     
      }                                                                         
                                                                                
    } 

... 

int my_handler(unsigned int fifo)                                               
{                                                                               
  struct my_msg_struct msg;                                                     
  int err;                                                                      
                                                                                
  while ((err = rtf_get(17, &msg, sizeof(msg))) == sizeof(msg)) {               
                                                                                
    rtf_put (msg.kanal + 1, &msg, sizeof(msg));                                 
    rtl_printf("FIFO send \"%d\" to task %d; period %d\n", msg.command,         
                                msg.kanal, msg.zeit);                           
    pthread_wakeup_np (tasks [msg.kanal]);                                      
  }                                                                             
  if (err != 0) {                                                               
    return -EINVAL;                                                             
  }                                                                             
  return 0;                                                                     
}                                                                               


I have cut some lines ;)

If I send the msg:
command 10 msg.period = 10000000
and sometimes later the msg
command 10 msg.period = 20000000
it works great

but if I send
command 13 msg.period = 0
it works, but if I send this msg a second time the task at
ret = pthread_wait_np(); 
will not wake up.

Has anyone a hint for me?

thank you
-- 
Juergen Liesmann
Hauptstr. 22
27248 Ehrenburg
Germany
Tel.: +49 4275 963030  Fax:  +49 721 151 203 706
Email: [EMAIL PROTECTED]
Web: http://www.ra-dec.de
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