Post by thread:hands causing interrupt to PIC16C73

I have a hairy problem. I wrote a program that waits in a loop for an interrupt to be generated from PORTB pins. When debugging the software everything is fine. However, when testing the hardware some unpredictable errors occur. That is specifically when you come close with your hands to the circuit inputs (PORTB <7:6>), an interrupt is generated making the circuit go haywire. If anyone had this problem before please some response will be readily appreciated. Franck. PS: Please use the same subject for mail sorting purposes. Thank you for your comprehension

>I have a hairy problem. I wrote a program that waits in a loop for an >interrupt to be generated from PORTB pins. When debugging the software >everything is fine. However, when testing the hardware some unpredictable >errors occur. That is specifically when you come close with your hands to >the circuit inputs (PORTB <7:6>), an interrupt is generated making the >circuit go haywire. Sounds like maybe you don't have all your pins tied down. Make sure you have ALL the pins on the pic (all the ones you aren't using for something else) tied either to high or ground through big resistors (10K works fine). CMOS chips don't like having floating pins. Dan

Put 0.1uF film caps on all and any input lines. This is common for any project you do. {Quote hidden}> -----Original Message----- > From: Dan Walkowski [SMTP:spam_OUTwalkowskTakeThisOuTINTERVAL.COM] > Sent: Wednesday, April 08, 1998 2:25 PM > To: .....PICLISTKILLspam@spam@MITVMA.MIT.EDU > Subject: Re: hands causing interrupt to PIC16C73 > > >I have a hairy problem. I wrote a program that waits in a loop for an > >interrupt to be generated from PORTB pins. When debugging the > software > >everything is fine. However, when testing the hardware some > unpredictable > >errors occur. That is specifically when you come close with your > hands to > >the circuit inputs (PORTB <7:6>), an interrupt is generated making > the > >circuit go haywire. > > Sounds like maybe you don't have all your pins tied down. Make sure > you > have ALL the pins on the pic (all the ones you aren't using for > something > else) tied either to high or ground through big resistors (10K works > fine). > CMOS chips don't like having floating pins. > > Dan

John Bellini wrote: > > Put 0.1uF film caps on all and any input lines. This is common for any > project you do. Not mine. I do however put 0.1uF ceramic (not film) caps on the +5V. It's easier to reprogram the (presumably unused) inputs as outputs. Then no pull up resistors or filter caps are necessary.

Franck, Sounds like PB6 and 7 are floating or very high impedance. Have you left PB7 and 6 as floating inputs? - what's connected to them? Steve Lawther ______________________________ Reply Separator _________________________________ Subject: hands causing interrupt to PIC16C73 Author: MIME:frougi01KILLspamUTOPIA.POLY.EDU at INTERNET-HUSKY Date: 09/04/98 09:31 I have a hairy problem. I wrote a program that waits in a loop for an interrupt to be generated from PORTB pins. When debugging the software everything is fine. However, when testing the hardware some unpredictable errors occur. That is specifically when you come close with your hands to the circuit inputs (PORTB <7:6>), an interrupt is generated making the circuit go haywire. If anyone had this problem before please some response will be readily appreciated. Franck. PS: Please use the same subject for mail sorting purposes. Thank you for your comprehension

Hi. What is causing the interrupt must be the static charge of the hand (or some martians maybe...). Try putting a couple of pF and a couple of kOhm to the ground, this might help. Your input pin must be left floating (or real close) to be disturbed by the proximity of your hand. Jacques. > {Original Message removed}

At 02:25 PM 4/8/98 -0700, you wrote: >>I have a hairy problem. I wrote a program that waits in a loop for an >>interrupt to be generated from PORTB pins. When debugging the software >>everything is fine. However, when testing the hardware some unpredictable >>errors occur. That is specifically when you come close with your hands to >>the circuit inputs (PORTB <7:6>), an interrupt is generated making the >>circuit go haywire. > >Sounds like maybe you don't have all your pins tied down. Make sure you >have ALL the pins on the pic (all the ones you aren't using for something >else) tied either to high or ground through big resistors (10K works fine). > CMOS chips don't like having floating pins. > >Dan > I set all unused pins to outputs to prevent ESD damage and noise pickup. Anybody want to flame me on this?