My project is as follows:

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I need to choose an USB-to-UART converter to be able to communicate with an MCU from my PC through a serial interface. I was thiking of using this part : FT234XD-R (datasheet).

I have one question: Can this chip be interfaced with a 3.3 V MCU?

In the datasheet they give application examples: USB-to-RS232, USB-to-RS422 and USB-to-RS485 converters, but they do not give a USB-to-UART converter example. I need to make sure that the voltage levels of the RXD/TXD pins can be handled by my MCU, for example I know that RS232, RS422 and RS485 voltage levels cannot be handled by a 3.3 V MCU.

  • \$\begingroup\$ You may be interested in the difference between UART (the communication protocol) and RS232/422/485 (electrical standards), in this linked answer. Designers almost always skip converting to RS232 voltages when connecting two UART ports on a single board, as it's overkill for short distances. electronics.stackexchange.com/questions/110478/… \$\endgroup\$
    – Willa
    Commented Jul 6, 2022 at 15:55

1 Answer 1


It's safe to use with an MCU directly. This is what the chip is designed for.

Apply 3.3V to VCCIO for 3V3 logic, or use the on-chip regulator by shorting the 3.3VOUT pin (pin-3) to VCCIO pin (Don't forget to place a decoupling capacitor to this pin). You can use the on-chip 3V3 regulator to supply your MCU and externals if the total consumption is less than 50 mA.

If you want to convert the logic-level RX/TX signals to RS-232, -422, or -485 then use an extra transceiver such as MAX232, MAX485, etc.


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