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interfacing 3.3V and 5V microcontroller

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icemetal

icemetal

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I have this 2 MCUone works with 3.3V and the other with 5V and I want to send a signal from the 5V MCU to the 3.3V MCU, what can I do with out burning the 3.3V MCU?

here is my circuit

Clipboard01.jpg
 

if you are sending from the 5 volt uC only then just use voltage dividers


but if you send from the 3.3 too you will need buffers
 
If you just want to send from the 5V to the 3.3V, then use a potential divider.

The first method on this page:

**broken link removed**

---------- Post added at 19:32 ---------- Previous post was at 19:28 ----------

To send from the 3.3V to the 5V, read my post (post 2) here:

https://www.edaboard.com/threads/241723/
 
Assuming that there is a pullup in the target side pin it will but you will get an inverted signal
 

Thank you, what I mean, do I need to put a resistor between the divider and the transistor?
Clipboard02.jpg
 

**broken link removed**

u can use that method also.. play around with resistor value.. so you can get equal or less 3.3V.
 

You don't need a divider, a 10K resistor from U2 to the base will work fine.
If there is no pullup in U1 then connect a 10k resistor from the collector to 3v3 and connect the pic pin to the collector.

If you want to use a divider then connect the middle point of the divider directly to the pic
 

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