rs485 on nano
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No, connecting ground is not mandatory.. In fact, i would not recommend it at all, especialy not on longer bus lengts.. Just use A&B
If you have shielded cables.. Connect the shielding to gnd on 1 side only and leave the other side unconnected..
This will provide shielding but prevent ground loop issues.
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Also keepin mind that those cheap rs485 adapters have a 120ohm load resistor and pull up and pulldown resistors installed for the rs485 bus..
Those should only ve installed on the ends of the data bus.. So remove them from the rest of the adapters if you use more than 2.
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@Reza Though your two pictures are both bus topologies, your first one is a star bus topology and your second is a linear bus topology. As to your second question "so in end of A and B , what am i do ?" Depending on a few factors such as equipment connected, cable type, cable length and data speed (baud rate) used, you may or may not need a termination resistor at the end of the line. For short runs you typically won't need them, but if you have hundreds of feet you are working with, you may want them, especially if you want to run at a higher baud like 115200 or higher. As to the resistor value, just do a google search for "RS485 termination resistor."
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