[En-Nut-Discussion] GPIO Powersupply

Landsperger, Werner Werner.Landsperger at cassidian.com
Wed Jun 8 08:44:31 CEST 2011

Hi Ole,

meanwhile I can answered the question by myself. I've read just 5V but like you said in most cases (also ethernut3) there are 3.3V with a tolleranz of IO of 5V. So erverything works. 

By the way, using a voltage divider wouldn't be the best solution for signal processing. That was the reason of my question. 

despite of that thanks a lot! ;)



-----Original Message-----
From: en-nut-discussion-bounces at egnite.de [mailto:en-nut-discussion-bounces at egnite.de] On Behalf Of Ole Reinhardt
Sent: Tuesday, June 07, 2011 4:03 PM
To: en-nut-discussion at egnite.de
Subject: Re: [En-Nut-Discussion] GPIO Powersupply

Hi Werner,

> just a short Question:
> The Voltage of GPIO Pins are 5V right? Can I manipulate this voltage?
> For example to 3.3V?

Which architecture you are using?

On AVR GPIO voltage is 5V in most cases. Better said: same as the power supply of the CPU (some AVRs can be powered with 3.3V too, in this case you will have 3.3V GPIO voltage.)

On ARM most CPUs use 3.3V as GPIO voltage. Some architectures support 5V tollerant input pins. But carefully read your CPU manual before connecting any 5V signal to a 3.3V GPIO line!

If you have a 5V GPIO signal you could use a logic level translator to generate your 3V signal.

The most simple one is just a voltage divider (two resistors). But better use some specialised ICs like 74LVC8T245. 

There also exists specialised ICs for SPI busses or I2C busses that can be used bidirectional.

If you could specify your problem (little schematic for example) we could perhaps give you a better hint...


Ole Reinhardt


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