[En-Nut-Discussion] GPIO Powersupply

Ole Reinhardt ole.reinhardt at embedded-it.de
Tue Jun 7 16:03:01 CEST 2011

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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