ADM2486 with i.MX8M plus

Hello

I want to use ADM2486 with i.MX8M Plus. But I'm not familiar with RS-485.

Please let me know how to control "RE".

Is it OK to connect RE and DE, or do I have to control using GPIO?

I'll use Linux Ubuntu.



added OS info.
[edited by: ms-ms at 8:54 AM (GMT -5) on 10 Nov 2021]
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  • Hello, thanks for your query,

    ADM2486 is a half duplex RS-485 transceiver, so the same A/B signal lines are used for both transmitting and receiving, but not at the same time. The device must be configured to either transmit or receive, DE and #RE pins are used for this flow control. Typical half duplex connection is to connect both #RE and DE together, and control from the processor using a single transmit/receiver signal (DE/#RE). 

    When DE/#RE signal is driven high by the processor, the ADM2486 is in transmit mode, all data applied to the TxD pin will be send to the RS-485 bus, and the RxD receiver output will remain inactive. When the DE/#RE signal is driven low by the processor, the ADM2486 is in receive mode, all incoming data from the RS-485 bus will be received at the RxD pin, and the TxD transmitter input will remain inactive. 

    In this configuration it's worth adding a weak pullup resistor to the RxD pin (eg. 47kohm) to pull this high when the receiver is inactive. 

    The DE/#RE pin can be driven by a GPIO, or some UART blocks have the facility to drive this pin, usually listed in the UART manual as "hardware flow control" 

    Regards,

    Neil 

Reply
  • Hello, thanks for your query,

    ADM2486 is a half duplex RS-485 transceiver, so the same A/B signal lines are used for both transmitting and receiving, but not at the same time. The device must be configured to either transmit or receive, DE and #RE pins are used for this flow control. Typical half duplex connection is to connect both #RE and DE together, and control from the processor using a single transmit/receiver signal (DE/#RE). 

    When DE/#RE signal is driven high by the processor, the ADM2486 is in transmit mode, all data applied to the TxD pin will be send to the RS-485 bus, and the RxD receiver output will remain inactive. When the DE/#RE signal is driven low by the processor, the ADM2486 is in receive mode, all incoming data from the RS-485 bus will be received at the RxD pin, and the TxD transmitter input will remain inactive. 

    In this configuration it's worth adding a weak pullup resistor to the RxD pin (eg. 47kohm) to pull this high when the receiver is inactive. 

    The DE/#RE pin can be driven by a GPIO, or some UART blocks have the facility to drive this pin, usually listed in the UART manual as "hardware flow control" 

    Regards,

    Neil 

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