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I do have STM32F072RB microcontroller which works on 5V but also have output power pins on 3.3V.

I do have Wi-Fi module (ESP 8226) that works on 3.3V. I can power it with STM easily but what about UART pins? Will they switch themselves to 3.3V and work properly? When not, how do I connect RX and TX busses so they can work properly?

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  • \$\begingroup\$ I think you are confusing microcontroller power supply (which would probably be 3.3V in case of STM32F) with some development board power supply (likely 5V). That board will have internal power regulator that will lower voltage from 5V to 3.3V to power uC. Which means that you can connect both modules. Just remember to have their grounds connected. \$\endgroup\$ – mactro Dec 15 '16 at 14:37
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Well, I think this is not a question for stack overflow. But I give my opinion anyway. I think you got it wrong. The STM32F072 does not work on a 5V power supply. The power supply must be below 3.6V. Most of the IOs are 5V tolerant, which means that if you apply 5V on them, it will not break the device. So in your case, power the STM32 with a 3V3 power supply and its solves your issue!

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  • \$\begingroup\$ That's right, I thought that STM32F072 works on 5V and it turns out that it works on 3.3V actually. Thanks! \$\endgroup\$ – Tomek Dec 21 '16 at 16:32

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