Interrupt triggering by static ???? [solved]

I have a sketch running on mega 2560 and two interrupts executing update code, one of the interrupts (4 on p19) triggers sporadically if I run a wire accross any of the other pins and touch the conductor, I have tried Rising/Falling/Low scenarios using 220r resistor but the result is the same. The sketch switches the remaining pins high and low in a loop using port manipulation as well as there being an lcd matrix display, Any help appreciated !

T.

What is supplying the interrupt signal, and is there a pullup or pulldown resistor?

The interrupt is a push switch, I have tried pull up and down with 220r resistor connected to the ard 5v and gnd pins with rising and falling scenarios respec tively with the same result

t

tawn10: The interrupt is a push switch, I have tried pull up and down with 220r resistor connected to the ard 5v and gnd pins with rising and falling scenarios respec tively with the same result

t

also using internal pullup and both internal and external, lower r value minimises the effect ie it is worse with a 1k pullup

May be a hardware fault, I have just remembered that the reset button seems to be non functional, unless there may be a common reason for this to happen ??

Hi,

I have had interrupts triggered by switching in nearby wiring or ICs, in my case I was able to move my wires around to avoid the crosstalk - might be worth a try for you.

Duane B.

tawn10: The interrupt is a push switch, I have tried pull up and down with 220r resistor connected to the ard 5v and gnd pins with rising and falling scenarios respec tively with the same result

Can you draw a sketch (diagram) of your wiring? All this describing doesn't really work. And maybe post your code as well.

I will get a diagram together, the code is lengthy !

I have resolved the problem, In my port manipulation routine when closing a single port the loop was just setting all bits to zero, I masked the remaining bits and this resolved the problem, so to clarify an already low bit was being set to low in a loop. also altered the order in which pins were set high and low to reduce supply ripple.

T