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Problem with pin RB8 of DSPIC33FJ128MC804

bluesea

I use a dspic33FJ128MC804,

My problem is
When I 
1. Enable pin RB8 as output pin (TRISBbits.TRISB8 = 0 )
2. and set LATBBits.LATB8 = 1;

pin RB8 is set to 1. But after that it become 0, and 1 again,  (As figure)

----------------------                    -------------------------------
                        |                   |                                   |
                        |                   |                                   |
                       ------------------                                    ------------------------------------------

Sometime when I set it to zero, but it become 1 ...

But if I use a VOM or Oscilloscope to observer the logic of this pin, It will become Zero permanently
---------------------
                       |
                       |
                       |
                       --------------------------------------------------------------------------------------


How can I solve this problem?
I've read some thread in forum, I disable JTAG  (_FICD(JTAGEN_OFF)  but problem is still can't solve .

  • I guess your code is like this:

     

    TRISBbits.TRISB8 = 0;
    LATBBits.LATB8 = 1;
    LATBBits.LATB8 = 0;
    LATBBits.LATB8 = 1;
    LATBBits.LATB8 = 0;

    If the clock frequency is very high, can be dificult for the pin port to follow the instructions specialy if you have a capacitive load.

    You can try:

     

    a) A faster osciloscope (or a faster scope horizontal sweep speed)

    b) A x10 mode scope probe (usualy makes a lower capacitive load)

    c) To eliminate the last line  (LATBBits.LATB8 = 0;)  and see if the line stays at 1 (3.3V)

    d) What is the duration pulse you need?  Maybe you need a delay rooutine. You can try one of two aproaches:

    d1.

    TRISBbits.TRISB8 = 0;
    LATBBits.LATB8 = 1;
    LATBBits.LATB8 = 0; LATBBits.LATB8 = 0; LATBBits.LATB8 = 0; LATBBits.LATB8 = 0; LATBBits.LATB8 = 0; LATBBits.LATB8 = 0;
    LATBBits.LATB8 = 1; LATBBits.LATB8 = 1; LATBBits.LATB8 = 1; LATBBits.LATB8 = 1; LATBBits.LATB8 = 1; LATBBits.LATB8 = 1;
    LATBBits.LATB8 = 0;

    or:

     

    void MyDelay()

    {

      int delay1;

      for(delay1=0;delay1<1000;delay1++){};

    }

     

    main()

    {

      TRISBbits.TRISB8 = 0;
      LATBBits.LATB8 = 1;
      LATBBits.LATB8 = 0;
      LATBBits.LATB8 = 1;
      LATBBits.LATB8 = 0;
    }

     

    I hope one of the approaches should help.

     

    Regards,

    Luis