I have some nodes that are connected to a server with RS485. I use stm32f103 microcontroller with MAX485 in nodes. We use modebus connection. The driver is connected to a nano pi m3 as server. The baudrate is 115200.
The problem is that sometimes I lose a node. It means that I don't receive any data, not a wrong data. There is also no pattern, for example one day I don't receive data from first node and the other day I don't have data of the 3rd one. If it helps, I reset the system by unplugging it every day. Also the address of each node is identical.
I used a shielded twisted pair for rs485 and I connected the ground of nodes to the ground of driver. I also used two 120 ohm resistors to terminate the line,
one in driver and the other in the last node, the intermediate nodes do not have any 120 ohm resistors.
The question is that it may be a hardware problem or a software?
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N. Parsa
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I've had inconsistent data when there were unsoldered ground connections between the two terminal ends. each node had to be soldered to the main lead back to the collection device even when the wires were shielded. – trapspring Mar 27 '18 at 21:01