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I am using beaglebone with kernel 4.4. I am trying to use the RS485, with pin 9.11 and pin 9.13 for tx/rx, and pin 9.27 as a GPIO control for the DE/RE pin. I bought a SN65HVD72, and connect it as described. I hook up the bus line to an oscilloscope. When I set the DE pin to high, and do 'echo hello > /dev/ttyO4', I can see there is bits signal in the oscilloscope on the bus B. But I could not see anything signal with bus A. Is this correct?

How do I know the RS485 is functioning?

And also how to I control DE/RE pin so that when I have transmitted a data package, then it turns to receiver enable mode?

  • Forget to comment about my solution, which is quite simple that just buy a rs485 chip that supports auto-direction control. – Peilang Liao Aug 30 '17 at 15:01

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