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ISO1410: Connection to UART port

JH Shin
Guru 10070 points
Part Number: ISO1410

Tool/software:

Hello,

My customer wants to implement isolated UART to RS485 communication using ISO1410BDW.

Please tell us how to connect TXD, RXD, CTS, RTS of UART port to ISO1410BDW.

Thank you.

JH

  • 0
    Guru 306800 points

    The four UART signals are usually used with RS-232 and are unidirectional.

    RS-485 usually is a half-duplex bus for a single signal. It is possible to use these four signals independently; this is usually called RS-422, and you'd need two ISO1410 devices.

  • 0 in reply to Clemens Ladisch
    Guru 10070 points

    Hello Clemens,

    Thank you for your reply.

    Does this mean that users can't implement communication between UART and RS485 with MCU + 1 isolated RS485 tnasceiver(ISO1410BDW)?

    My customer wants to know how to connect DE, D, R, /RE of the circuit below with TXD, RXD, CTS, RTS of MCU UART.

    Thanks,

    JH

  • 0 in reply to JH Shin
    Guru 306800 points

    RS-485 is an electrical specification; it does not define the protocol of the data that is transmitted.

    What protocol are the other devices on the RS-485 bus using?

  • 0 in reply to Clemens Ladisch
    Guru 10070 points

    The customer wants to connect ISO1410 to UART port of below MCU to communicate. So they are asking for TI's guide on how to connect UART pins of MCU, TXD, RXD, CTS, RTS to ISO1410.

    Is protocol information absolutely necessary for connection guidance?

    Thank you.

  • 0 in reply to JH Shin
    Guru 306800 points

    With what other devices should this MCU communicate? It is not possible to communicate without knowing the protocol.

  • 0 in reply to Clemens Ladisch
    TI__Mastermind 25690 points

    Hello JH, 

    As Clemens has said, the RS-232 protocol describes a single-ended physical layer to communicate with one other device. ISO1410 is designed to support RS-485 and RS-422 which describe a differential physical layer that supports multiple devices on the same bus. 

    TXD, RXD, CTS, RTS are usually used with RS-232. However, you can map the pin functions to ISO1410 as shown below and the MCU will need to be configured to handle the ISO1410 signals since CTS and RTS aren't the same purpose as DE and /RE. DE and /RE can also be tied to VCC and GND respectably to set the driver and receiver to always be enabled.  

    MCU pins ISO1410 RS-485 logic pins
    TXD D
    RXD R
    CTS (clear to send) DE (driver enable - optional) 
    RTS (request to send) /RE (receiver enable - optional)

    Best,
    Andrew