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Translator for UART 5v -> 3.3v needed

Max-ksb
Prodigy 50 points
Other Parts Discussed in Thread: SN74LVC1G34, PCA9306, SN74LV1T34

Hello I need a translator for the  tx-rx line. Atmega328 TX (5V) -> ESP8266 RX (3.3V).

Which one should I choose. Made a selection here https://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=ed90d86c9e

Thank you

  • 0
    TI__Guru* 97066 points

    Hi Max,

    It looks like you ahve a buffer, a buffer with output enable, a NAND gate, and an AND gate selected in that link.  Since all four of those devices have different functionality, I'm not sure what to tell you.

    If you just want to translate 5V down to 3.3V unidirectionally (ie the signal never goes back from 3V to 5V), then I would recommend using the SN74LVC1G34. Just supply the device with 3.3V, and input 5V. The device will down-translate and the output will be at 3.3V.

    If you need to also up-translate from 3.3V to 5V, it gets a little more complicated (but not much). Let me know if you need that as well.

    You might find these videos interesting on how auto-bidirectional level translators work: The Logic Minute

    Some of the concepts apply across all translators.

  • 0 in reply to Emrys Maier
    Prodigy 50 points

    Hello, oh ok, I tried using your search and got those results. Ok thanks, thats great. You're right. The UART-signal (57600 baud) has to be translated from 5v down to 3.3. (TX 5V-powered Atmega down to RX 3.3V-powered ESP8266-Chip)
    That helped me.

    Maybe for the next time. Which one would you recommend for the other director? If I have to translate from 3.3 -> 5V? Signals are eg as in this case UART or could be in furure also I2C.

  • 0 in reply to Max-ksb
    TI__Guru* 97066 points
    For I2C I would recommend the PCA9306 - it's a device specifically designed for I2C applications.

    A generic 3.3V to 5V translator would be SN74LV1T34.

    Come back any time if you need help :)