Unused pins


Senior Member
I remember reading sometime ago that an unused pin on a PICAXE (I'm using an 08M), shouldn't be left "loose", but can't remember what to do...
Should it be tied to the ground or 5V ?



Senior Member
It depends on the application -these are not CMOS logic gates!In general unused pins can be left floating, but there may be power savings in some cases if pins are tied hi/lo. <b>What are you doing? </b>

Simple LED flashing/sounds/datacomms PICAXE circuits are not fussy,but READADC stuff can be due to stray signals. A weak but firm pullup/down via 10k Ohms is then usually attached to a pin. Of course you can force pins high or low under software too.

HTH ? Stan

Edited by - manuka on 29/08/2007 02:57:16


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Senior Member
Thanks Stan.
Some additional info: The unused pin will be Input3, so it can't be made an output. The lowest power consumption is also a requirement, so should it be better to tie it to ground or 5V ?


Senior Member
The answer is &quot;yes&quot;.

Whatever is closest on your circuit board. The input has a high impedance, once tied to either rail it will consume nanoamps (or less).