Hello
I try to connect UART/Serial connection to my board but i read that only 3.3v is allowed to connect. saddly my device work on 5-6v Serial.
Can someone confirm that Portenta H7 can only work with 3.3 volt devices ?
i dont want to burn it quick if something goes wrong.
To be sure, use the two channel logic level converter
thank you . I will try that but maybe someone already try or have some data what voltage range can be used on portenta H7 because i cant find any details . So probably also for this board if i want to program i2c eeprom have to get also level converter becasue they work on 5v?
See the datasheet
https://www.st.com/resource/en/datasheet/stm32h747ag.pdf
chapter 6.2 "Absolute maximum rating"
According to above, the maximum input voltage for most Potenta H7 pins is 4.0v, so you definitely need to use logic level converter
now is clear for me 
thank you for information and help