ATmega328 and w5500 - reset pin on 5v or 3.3.v?

Using Arduino Microcontrollers
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Hi :slight_smile:

My question:
If I have an Atmega328 and a w5500 on the same board, and I want to connect a reset button which will reset both at the same time, how do I do that, knowing one works at 3.3V and the other at 5V?

My speculations:
Looking at datasheet of the w5500, it says "3.3V operation with 5V I/O signal tolerance", so I guess that means I can send 5V to the reset pin and then connect both ICs from the same +5V Vcc with a pullup 10k resistor?

Isn't it correct that using an arduino and a w5500 ethernet module, you would connect the reset pins of both boards? In this case how does it work? My guess is the reset pin of the w5500 is connected to the 5V.

Looking at this schema for example:
http://wizwiki.net/wiki/lib/exe/fetch.php/osh:w5500_ethernet_shield:w5500_ethernet_shield_v10_sch.pdf

It looks like the reset pin on the w5500 is connected to the +3.3V but also connected to the reset pin on the arduino uno, which I know is connected to the +5V source, how does this work?!

Thank you so much in advance!!

Cheers
Simon

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Thank you for the quick reply spycatcher.

So something like this would work? (see attachment) Which diodes should I use?

Also, are the capacitors necessary? I added them because I often see a 100nF capacitor next to reset switches, I guess to avoid voltage fluctuations which could create a reset by mistake?

schematics.png
schematics.png772×503 21.6 KB

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And are you sure it would not simply be possible to drop the +3.3V and do it like this (attached), based on the w5500 datasheet saying "3.3V operation with 5V I/O signal tolerance"?

Thank you :slight_smile:

schematics-only5V.png

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That's great info mate thanks!!

I currently use an arduino and a w5500 module which from what I can see seems to have the reset pin of the w5500 directly connected to the RST pin of the module, and I connected this pin directly to the arduino Reset pin - that seems to work fine.
So I guess I'll try to simplify the setup and go for +5V on the reset pin.

PS: Just FYI your website www.uk-pcb.co.uk does not seem to respond - thought you might wanna know :wink:

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