Or i need to put them external?Thanks,
You can decide whether pull-ups are enabled or not when configuring each pin. See PORTn_PCRx register.
The pull-up resistors will have a wider tolerance spread than external ones though.
I agree with Mark. It is better to add external pull-up resistor. The internal resistor is a weak pull-up. So you need add a strong pull-up external to ensure communication is good on no good layout condition. Hope my reply can help you.
Thanks Mark and Paul,
I'll perform some tests using internal pullups, if i'll found problems i'll install external.
Will keep you updated
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