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CC1110: an I/O pin which has been configured as a output pin can cause an external interrupt ! why?

boomh
Prodigy 195 points
  • I am using CC1110 . I  use the P0_7 as an external interrupt source which connect with a  press button . so I configure  P0_7 as a input pin while all other pins of P0 as output pin, like this:

 P0SEL |= 0x03;  
  P0 |= 0x3f;      
  P0DIR |= 0x3f; 

the interrpt configration codes are the following:

   P0IF =0;
   P0IFG = 0x00;
 
   PICTL |= PICTL_P0ICON;        //fall edge
   PICTL |= PICTL_P0IENH;        

   INT_ENABLE(INUM_P0INT, INT_ON);

and the interrupt routine  are the following:

#pragma vector = P0INT_VECTOR
__interrupt void  KEY_ISR(void)
{
 
      INT_ENABLE(INUM_P0INT, INT_OFF);    
      if (P0IFG & BIT7)   {    //key
         
         P0IFG &= ~BIT7;      // Clear status flag for pin
         f_keyint = 1;    
      }
      else if (P0IFG & BIT6)  
         P0IFG &= ~BIT6;   

      else if (P0IFG & BIT5)   
         P0IFG &= ~BIT5;   
      else if (P0IFG & BIT4) 
         P0IFG &= ~BIT4;    
      P0IF =0;              // Clear CPU interrupt status flag
      INT_ENABLE(INUM_P0INT, INT_ON);
 }

at this time， a unusual phenomenon  presented : before  I press the button , external interrupt  occoured  frequently . the interrupt source is P0_5 or P0_4 .

what does the phenomenon mean?

any ideas? thanks a lot !

  • 0
    TI__Genius 12900 points

    What are pins P0.5 and P0.6 connected to on your board? Do you see any noise on these pins?

    From what I see, your code looks ok. However, the CC1110 datasheet states in section 12.4.4 that you should always clear the IO module's interrupt flags (P0IFG register) prior to clearing the CPU's interrupt flag (IRCON.P0IF). Another tip, you should implement some kind of software debounce on your button to be sure a single button click doesn't trigger multiple interrupts.

    Br,
    ABO 

    --
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  • 0 in reply to TIABO
    Prodigy 195 points

        thank you for your reply!

        now  the phenomenon  presented  enen when  I  connect nothing  at all  I/O ports.  (all pins are  impending ). It seems that  pressing key  is not needed   that the external interrupt  occoured  over and over. It  looks like it  works by itself .

       Regards:

       bob hong

  • 0 in reply to boomh
    TI__Guru* 86241 points

    Hi

    For Port 0 and port 2 you can only enable/disable interrupts for 4 and 4 pins at the time. That means that is interrupt is enabled for let's say port0 pin 4 - 7 any activity on either of these pins will cause an interrupt, even if the pin is configures as an output.

    If you use port1 instead you can enable/disable interrupts for each and every pin.

    Br

    Siri

  • 0 in reply to Siri
    Prodigy 195 points

    thank you ! I think this is not very convenient for a designer. I have to change my design again!

  • 0 in reply to Siri
    Prodigy 100 points

    Hi Siri
       I agreed with you.

       I designed it as either read or power supply in one grounp at the same time, for example , P0 for reading data, and P1 for power supply or interrupt.  there is a little bit complicate for designed of mutiple sensor or logical.