Hi,
i have a STM32F407VGT6. It have 5 volt tolerant input/output pins. I want to do RS485 communication using MAX485. But the Max485 logic is 5v. And my mcu have 3.3v logic. so i want to know can i use two 5 volt pull up(10k) in the RX TX pin of the mcu ?

I will not use it for long time,i will just use this for testing purpose. can i do that ?

in my logic when ever the mcu will provide high logic the max485 will detect logic high of 5v beacuse of the pull up,and when the mcu will provide logic low,the max485 will receive logic low,cause the pull up resistance is 10k.

 

hi Ehsan,
Welcome to AAC.
I use these low cost bi-directional level shifters, I have one running at 20MHz.

https://www.amazon.co.uk/TOOGOO-cha...264&sr=8-3&keywords=bidirectional+logic+level

Also eBay
https://www.ebay.co.uk/sch/i.html?_...GOO(R)+4+channel+logic+level+shifter&_sacat=0

E

 

You should be able to just hook it on to your STM chip if the port pins are 5V tolerant.
The MAX485 input signals need to be over 2V for a High, so 3.3V will be fine.
No pullups or level shifters required.

 

@dendad... thank you i will test that and let you know