Voltage Shifting > Arduino Uno 4 is 5v only?

[InfiniteBSOD]

Hello,

My first foray into this so bare with me if I have misunderstood something.
I am really not trying to come across as a "wise-a**" but just want to understand so please read the post in the spirit I wrote it.

I am looking for hardware to run JTAGenum on and was almost ready to hit the "purchase" button on the Uno Rev4 WiFi / BT.
However I upon further research it only supports 5v and not 3,3v & 5v.
Well ok "The R4 Wi-Fi does have a pair of 3.3 V GPIOs in the Qwiic connector which should make it easy to connect to I2C hardware, especially those with a Qwiic or STEMMA QT connector. However, this isn’t on the Minima. Otherwise, you need to ensure that any hardware you want to use is compatible with 5 V."

So unsure if you can use those specific GPIO's since the Qwiic-connector doesn't seem to be a standard GPIO-pin?

Looking here:
https://github.com/cyphunk/JTAGenum/wiki/Embedded-Analysis#voltage-shifting
this phrase here gave me a bit of head-scratching:
"For 3.3v and 5v targets, you can use either Arduino or RaspberryPi without modification.
Some Arduino boards are switchable between 3.3v and 5v."

So the first sentence in that quote says you can use Arduino or RPi "as-is".
The second sentence says that some Ardunio's are switchable between 3,3 and 5v.

I would pref run JTAGenum on a device that offers both 3,3v and 5v without having to solder anything, possibly just adding a "shield" which I understand is something you can "snap on" if you buy the shield pre-assembled. Any suggestions?

I don't actually know what voltage (3,3 or 5v) the devices I will run JTAGenum against will have.
I checked on my first "use-case" and err....the voltage adapter is 12v but guess that doesn't say anything about the actual UART-pinout voltage?

Sorry for rambling, just trying to make an informed decision on which board to purchase to cover both 3,3v and 5v and that won't require soldering.

Best Regards and thank you in advance - InfiniteBSOD

[cyphunk]

I'm sorry for the long delay. I work at an art supply shop these days so rarely get in front of a computer.

I see how the language around device voltage compatibility is confusing. I can't quickly resolve the confusion because it is true that there are many Arduino versions with different voltage level logic. The Uno, if I remember, is really just 5v. The Arduino Mini can be purchased in 3.3v or 5V versions (and with some physical modification could be switched). The Teensy clones are 3.3v.

In some target case that expect 5v logic levels you may find they detect 3v signals as well. This is because the target determines a HIGH bit based on a voltage range and sometimes that range is 2.2v up to 5v in 5v targets. See this image from here which shows some logic level specifications where you can more clearly see overlap:

From that image you can see that if a CMOS 3.3v device sends a signal to a TTL 5v device the TTL device will have no issue detecting HIGH (1) and LOW (0). When the TTL responds with 5v signals to the CMOS 3.3v device we might have issues, or we might not. It will depend on the tolerances of the CMOS device, its processor and supporting component tolerances. Will they overheat and become damaged? Or will be survive. Its generally not advised to push it.

I find it best to have multiple Arduinos in my toolkit which each have different native voltages and I choose the one that matches the target im attaching it to.

About raspberry Pi. All of its GPIO's are at 3.3v.

I hope this helps