Maybe this can help....
Schematic diagram for connection MAX485 ili more popularat 75176 IC to any AVR.
No need for special pins for controllin data flow in or out. This isa hardware auto switch, I had tested severely on many projects...
Jumpers
J1,J3 : 485 bus suppy ! Only on master device and MUST be jumpered.
J2: bus terminator. MUST if your device is at end off 485 bus. (first or at end)
ALSO very important. If possible, try to always use shielded cable, so with TREE wires. R6 should be at least 0.5W !!! Without this resistor is possible but have to be carefful fg flying GND's currents if connecting two electrical different words.
Regards !
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