John,

1. do you have pull up resister on porta,0.
2. how are you driving the buzzer. you should
    use a transistor with it.
  so far is hardware problem unless you didn't mention all this.

Andre





John Esposito wrote:

> I am a beginner at PIC programming and built a test circuit using the
> 16C84.  The circuit uses a magnetic switch for an input and when the switch
> closes, and LED and piezo buzzer turn on.  Simple right?  Well, not for me!
>
> Here is the problem:  when I physically move closer to the breadboard (with
> the mag switch open), the LED turns on (but not the buzzer), getting
> brighter as I get closer to the breadboard.  Once this happens, the
> operation of the circuit is all messed up.  If I close the switch,
> sometimes the LED goes on, sometimes the buzzer sounds, sometimes both, and
> sometimes the LED works opposite, i.e. when the switch is open, the LED is
> ON, and vice-versa.
>
> Brief description on the circuit:  10 MHz Crystal (ECS) w/ 33 pF caps
> directly to ground; PORTA<0> switch input, PORTA<1> led output, PORTA<2>
> piezo output.
> LED output feeds an 74HC04 inverter; output of inverter to LED cathode; LED
> anode through 100 ohm resistor to +5V.  All unused 74HC04 inputs direct to
> ground.  All unused PIC I/O are configured as outputs and left unconnected
> to anything.  !MCLR pulled up to +5V.
>
> As for hardware, I configure the I/O ports on reset, and basically run a
> tight loop scanning the inputs, and changing the outputs based on the
> input.
>
> Any ideas?  Hardware or software?  I can't do much else until I figure out
> what is going on here.
>
> Thanks in advance for the help.
>
> --John