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UART RS422 Interface (full Duplex) using SN65HVD1791

Oliver Borges
Prodigy 10 points
Other Parts Discussed in Thread: SN65HVD1791

Hello,

we are looking for a short application note / schematic how to design a uart (5V microcontroller Rx & Tx) to RS422 (one differential pair for Rx, one for Tx) full duplex Interface.

We found the SN65HVD1791 but beed some advise for the design.

Could you provide us an example circuit, please?

Thanks in advance,

Yours faithfully

Oliver Borges

  • 0
    TI__Guru 62920 points
    Hi Oliver,

    I'm not aware of any application notes on this topic in particular, but if you have some questions on how to proceed we would be happy to try to give some guidance. Typically for this kind of application there is not a lot of complicated circuitry - the microcontroller will interface to the single-ended IO of the RS-485 transceiver (like D, R, DE, and /RE), and the differential signals will connect to the bus. For a full-duplex point-to-point link, RS-422 will be terminated using a 100-Ohm resistor placed across the A and B inputs at the receiver. If the application requires extended protection against electrical transients (like ESD events or surges) beyond what is handled by the transceiver, external protection devices like transient voltage suppressors may be placed on the bus as well.

    There is a good selection of general application notes on RS-422 and RS-485 here:
    www.ti.com/.../rs-485-technical-documents.page;docCategoryId=1

    If you have any other questions, please let me know.

    Regards,
    Max