3.3V Nano every?

Hardware Nano Family Nano Every
1

I am trying to make a board based on nano every and communicate with several I2C and SPI device. Most of the device runs at 3.3V but the nano every runs at 5V.
I saw some discussion that the nano every can also runs at 3.3V but the clock frequency will need some configuration.
Nano every at 3.3V - #10 by eslavko demonstrated the 3.3V operation of nano every.
Custom Arduino Nano Every at 3.3v discussed about the clock configuration needed.

I am going to keep the USB 5V as well as other potential 5V source and use the switcher to generate 3.7V and LDO to 3.3V at up to 2A.

Later, maybe also add a VCXO as extclk source to pin 44, controlled by a I2C DAC, and try to play with it later to see how fast can I push the SPI, I2C speed.

Am I missing anything?

One question is about the UPDI, if I am powering the ATMEGA4809 at 3.3V, will the UPDI pin tolerate 5V if that is come from other programmer? At least I need it at beginning to program the ATSAMD11, bootloader.

2

Check the ATmega4809 data sheet. I imagine that the answer is no.

3

Just use level shifters

4

From ATMEGA4809 datasheet, it seems OK to program at 3.3V, except it can be a little slower than 5V as it can not support 1.8Mbps.

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5

It seems the UPDI is the only pin might need level shifter to protect from outside?
Do I really need the level shifter on it?

6

It depends on what speed you want

7

Yes.
That's what you do.
It's not a big deal - especially considering the 'alternative' (all this updi dickering etc).

8

Why don't you just use a 3.3V programmer?
Then you won't need any additional hardware or translators

9

Yes. When connecting a 5V output to a 3.3V input, ALWAYS use a level shifter, unless the manufacturer clearly states that the pins on a 3.3V part are "5V tolerant".

10

@sonofcy 0.9Mbps seems good enough for me.

11

@jremington Thank you for the reply.
I understand the concept. In this case, the ATMEGA4809 itself are all "5V tolerant" because that is the original design voltage as used in Nano Every.
I am trying to reduce the voltage to 3.3V so all the sensors etc do not need the level shifter.

12

Why don't you just use a 3.3V programmer?
Then you won't need any additional hardware or translators
[/quote]

@jim-p Thank you for the suggestion.
Yes, since the ASMD11, which is going to be the programmer for the ATMEGA4809, is at 3.3V so in normal operation, that should do the job?
I am concerning on people used to use whatever UPDI programmer they are used for the nano every and connect to this board directly.[quote="jim-p, post:8, topic:1320389, full:true"]

13

ONLY if it is powered by 5V.

If it is powered by 3.3V, then the absolute maximum voltage you can apply to any pin is 3.8V.

This is made very clear in the ATmega4809 data sheet.

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14

Same is true for any board not just your design. Most FTDI programmers have a jumper for 3.3V or 5V. You need to instruct the person doing the programming to use a 3.3V programmer for your board