Never mind. We will be gentle. :)

First thing first, what is pin 0?
>From Datasheet ( not all the alternative functions are listed here) :
Pin 1: Vdd
Pin 2: GP5
Pin 3: GP4
Pin 4: GP3 (input only) or /MCLR 
Pin 5: GP2
Pin 6: GP1
Pin 7: GP0
Pin 8: Vss

So please re-describe your connection using this pin definition
in the datasheet. Another thing is the configuration?

Regards,
Xiaofan

-----Original Message-----
From: Andrew [mailto:andrew@ugh.net.au]
Sent: Monday, August 22, 2005 4:56 PM
To: piclist@mit.edu
Subject: [PIC] finger triggered circuit


Hi,

This is my first PIC project so be gentle! :-)

My circuit consists of a 12V battery (giving off 13V according to my 
meter) connected to a 7805. The 7805 has a 35uF capacitor from ground 
to output. The multimeter says the output voltage is 4.98V. This 5V 
supply is connect to a 12F629 which has LEDs on pins 2 & 4 and a DC 
operated piezo on pin 5 (the LEDs and piezo are just for debugging - 
I'll try to do something useful when this works!). pins 0, 1 & 3 are 
configured as inputs. Pin 0 is tied to -ve, 1 & 3 are unconnected. All 
this is wired on a breadboard.

My problem is that the chip doesn't always seem to start - it's 
programmed to give a short burst on the piezo at boot. The thing that 
makes it start when it doesn't want to is me placing my finger above 
the chip (sometimes I need to actually touch the plastic case of the 
PIC). Even once booted nothing much works but one problem at a time :-)

Having a look on the web I find the piclist page re floating inputs 
with the line:

"Some of these chips froze just  by placing a finger near them, some 
won't start, some start but run 'funny'."

Seems to be my problem however all the internal pull-up resistors 
should be enabled - WPU is 0x37, OPTION_REG is 0x7F - so all inputs 
(apart from GP0) should read as 1 if I have understood correctly.

Any suggestions?

Thanks,

Andrew

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