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Configurable for RS-422 ?

Walter Wang
Prodigy 20 points

Other Parts Discussed in Thread: OMAP3530

I have an application where I will use the beagleboard or gumstix (OMAP3530) to  communicate with an RS-232 device and RS-422 device. I have been unsuccessful in finding any information regarding RS-422 support. Can anyone tell me whether the OMAP3530 can be configured for RS-422? If so , would it be as simple as an ioctl function call? Thanks alot.

  • 0
    TI__Mastermind 41665 points

    My understanding of RS-422 is that it requires different hardware (differential drivers) than what is available with the standard RS-232 UART interface the OMAP3530 boards typically provide. This being said you would need some external adapter to use RS-422 (a quick Google search turns up dozens of these).

    On the positive side, my understanding of the RS-422 adapters is that they are directly compatible with RS-232, such that if you had one you would be able to leverage the existing UART drivers, unless you had some specialized protocol you needed to use on top of the RS-422 interface.

  • 0 in reply to Bernie Thompson TI
    Prodigy 20 points

    Thanks for the helpful quick response.

     

     

  • 0 in reply to Bernie Thompson TI
    Prodigy 10 points

    You must have correct hardware driver for the RS-422 interface.

    http://en.wikipedia.org/wiki/RS-422

    Voltage Levels −6V to +6V (maximum differential Voltage)
    Mark (1) Negative Voltages
    Space (0) Positive voltages

    The powerswing is maximum +/- 6 volt as the RS-232 can have up to +/- 15 volt and RS-422 has differential signals both for TX and RX.

    http://en.wikipedia.org/wiki/RS-232

    There should exist a simple adapter that is able to handle signals directly from MCU given voltages and power the RS-422 to correct levels.

    Think that RS-485 uses currents..

    Voltage levels -7 V to +12 V (Common Mode)
    6 V Max (Differential)
    Receiver levels:
     Binary 1 (OFF)
    (Voa-Vob < -200 mV)
     Binary 0 (ON) (Voa-Vob > +200 mV)

    So use the correct chip for correct interface or take care of the different with external components.