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PICList Thread
'need help for RTCC'
1999\11\11@153808 by hanjay chen

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<x-flowed>All,
   i am doing an experiment, using RTCC as an input counter from a push
button, and output to a 7-segment LED. the problem is when i push the input
button, i can't see any increment from the display. but it does increase the
count when everytime my finger touch the input pin or wire, or pull out the
input wire and insert back to the board and push the button. i have no idea
what happened to this, anyone can help me, thank you!
    for the "option" function i set it as "3Fh", ic=pic16x55, Xtal=8 MHz.

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</x-flowed>

1999\11\11@154432 by Harrison Cooper

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Is the switch grounding the input (typically how I would do it), and a pull
up on the input pin?

ie....it sees a logic hi normally, and pulls low when the switch is
activated.

1999\11\11@155513 by Quentin

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face
If you use the external TMR input, treat it like any other PIC input.
> but it does increase the
> count when everytime my finger touch the input pin or wire
Which tells me you are not using a pullup resistor, or if you switch
positive through the switch, you are not using a pull down resistor.
`>10K to <100K should do.

Quentin

1999\11\11@212204 by spamdogg

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   You might try to decouple the circuit.  Use a .1uF cap evey 2'' in both
directions on the board.  Also a finger touch or probe touch to a circuit causes
a response by the circuit because you or the probe are close to ground and when
the circuit is touched the current and voltage values can change.  Try the
decoupling and simulate the code on MPLAB.

Scott

hanjay chen wrote:

{Quote hidden}

1999\11\11@213453 by Mark Willis

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Can you tell us how the input circuit's set up?  (I'm suspecting
something like no pull-up resistor, do you have a resistor pull-up to
Vcc then the switch to ground or something?)  If that resistor's not
there, you get "unexpected" results (I think I just haven't remembered
your circuit from earlier <G>  Spend today fixing phone lines in rain &
wind, a little tired.)  Decoupling definitely, if a pull-up's there <G>

 Mark

Scott wrote:
>
>     You might try to decouple the circuit.  Use a .1uF cap evey 2'' in both
> directions on the board.  Also a finger touch or probe touch to a circuit caus
es
{Quote hidden}

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1999\11\12@181938 by hanjay chen

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<x-flowed>>Can you tell us how the input circuit's set up?  (I'm suspecting
>something like no pull-up resistor, do you have a resistor pull-up to
>Vcc then the switch to ground or something?)  If that resistor's not
>there, you get "unexpected" results (I think I just haven't remembered your
>circuit from earlier   Mark

THANK YOU MARK!
  I didn't put any resistor btw Vcc and input switch at the first time,
after you told me, i tried. here was how i wired the input switch.  GND-->
Push button switch-->RTCC pin(#1)
  Second Time:
        GND--> Push button switch ==> RTCC/22kohm -->Vcc(+5V)

Result is: still the same.... :( , it doesn't count, and only count when my
finger touches the lead(RTCC). I also found, when i hold the lead(RTCC input
wire) it counted so fast and the light so dim almost couldn't see from the
7-Segment LED, and i didn't push the input button only hold the lead(RTCC).
       Is there anything wrong, can anyone tell me where i did wrong at the
input circuit. Thank You Very Much!!!

Tools i am using: PIC-ICE for PIC 16XX


>Scott wrote:
> >
> >     You might try to decouple the circuit.  Use a .1uF cap evey 2'' in
>both directions on the board.

Dear Scott, I am using a breadboard for the wiring, can u help me how to
decouple the circuit and both directions, and i am not kinda lost here.
Thank You for your help!!!

 Also a finger touch or probe touch to a circuit causes
{Quote hidden}

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</x-flowed>

1999\11\12@201441 by Jinx

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It sounds as though the RTCC is counting or at least reacting to mains
hum on your finger. In that case, could I suggest the obvious, that is, get
the multimeter out and check all wire and components. Have you actually
measured Vcc voltage on RTCC ? It would seem the pin is floating.

Jinx

>    Second Time:
>          GND--> Push button switch ==> RTCC/22kohm -->Vcc(+5V)
>
> Result is: still the same.... :( , it doesn't count, and only count when
my
> finger touches the lead(RTCC). I also found, when i hold the lead(RTCC
input
> wire) it counted so fast and the light so dim almost couldn't see from the
> 7-Segment LED, and i didn't push the input button only hold the
lead(RTCC).
>         Is there anything wrong, can anyone tell me where i did wrong at
the
> input circuit. Thank You Very Much!!!
>
> Tools i am using: PIC-ICE for PIC 16XX

1999\11\12@201650 by Jinx

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BTW, you say you can hold the lead on RTCC. How long is it ?

Jinx

>    Second Time:
>          GND--> Push button switch ==> RTCC/22kohm -->Vcc(+5V)
>
> Result is: still the same.... :( , it doesn't count, and only count when
my
> finger touches the lead(RTCC). I also found, when i hold the lead(RTCC
input
> wire) it counted so fast and the light so dim almost couldn't see from the
> 7-Segment LED, and i didn't push the input button only hold the
lead(RTCC).
>         Is there anything wrong, can anyone tell me where i did wrong at
the
> input circuit. Thank You Very Much!!!
>
> Tools i am using: PIC-ICE for PIC 16XX

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