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I am working on Rs485 protocol using PIC24f microcontroller and sp3485c as rs485 transceiver ic . I have kept one pic as master and another pic as slave . when i am transmitting any data from master my slave is not receiving any data it shows junk data by (testing in debugger pickit3). Please suggest me how to solve this issue?

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  • \$\begingroup\$ Does it work when you just connect the Tx and Rx pins of the micros directly, leaving out the RS 485 driver chips? \$\endgroup\$
    – tomnexus
    Dec 29, 2015 at 6:36
  • \$\begingroup\$ ya by connecting tx and rx pins directly it is receiving data... \$\endgroup\$ Dec 29, 2015 at 6:50
  • \$\begingroup\$ Do you keep the RE' and DE high on one chip, and low on the other, without changing them? These chips might take a while to turn the bus around, so you can't just change it for the length of one byte. Also, are you using a reasonable data rate? \$\endgroup\$
    – tomnexus
    Dec 29, 2015 at 10:42

1 Answer 1

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This is the most common method of interconnecting RS485 devices: -

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Note two important things: -

  • 0V is common to all slaves and master
  • End-of-wire termination resistors (LT) are used

Here's another example: -

enter image description here

And another here that tries to avoid earth fault currents in an installation: -

enter image description here

This one is quite pretty too: -

enter image description here

Note that the black circles around the red and green pair imply a screened cable that is earthed.

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