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THVD1426: How to achieve auto-direction control by using THVD1426

Gary Zeng
Intellectual 1860 points

Part Number: THVD1426
Other Parts Discussed in Thread: THVD1406, THVD1450

Hi team,

My customer wants to use THVD1426 to achieve auto-direction contorl for half-duplex RS485.

image.png

As you can see, customer needs to use 1x GPIO from MCU to control direction. Customer doesn't have enough GPIO on MCU. And customer doesn't want to use full-duplex device.

Do we have relevant design to achieve auto-direction control of THVD1426?

  • 0
    TI__Mastermind 25192 points

    Hi Gary,

    Please reference this auto direction control app note as the customer seems to not understand it: https://www.ti.com/lit/an/slla574/slla574.pdf 

    THVD1426 (or THVD1406) can have /RE and /SHDN tied to GND. Both of these auto direction transceivers do not need any GPIO control from the MCU to change the driver/receiver direction.

    Another common approach is that they can use a regular half duplex transceiver like the THVD1450, where they can tied the DE and /RE pins together. This common RS-485 direction implementation makes it so when the line is high, the driver is enabled and receiver is disabled. And vice versa, when the line is low, the driver is disabled and the receiver is enabled.

    Best,

    Ethan