CODEWITHSUNDEEP
linuxserial-portmodbusrs485libmodbus
Achim
Achim

Reputation: 442

Timeout Modbus RTU Devices after reconnect RS232/RS485 Adapter

I've problems with a MODBUS RTU connection to devices after a disconnect & reconnect of the RS232. The system is build up the following way:

In general this works fine, even over weeks. But once one disconnects the RS232 cable and reconnects it after some seconds (or minutes or hours), the libmodbus gets timeout-errors on every access to the MODBUS device. This is very annoying, because it is difficult to get it back to work again. Only a lot of further disconnects of both ends of the RS232-RS485-Adapter will bring it back, after some minutes and up to 10 retries.

Any idea what could cause this problem?

Any help what to do to prevent this and immediately work after reconnect the RS232 cable?

(Yes, one possible solution is to simply let the RS232 cable be always connected. But sometime somebody need to do something and forgot about the consequences - I think this is not a realistic option)

Upvotes: 0

Views: 677

Answers (1)

Achim
Achim

Reputation: 442

I've got an solution, with help of mikrocontroller.net forum:

Using another RS232 → RS485 adapter DeLock 62919 and powering with +5V on the clamps by dedicated power-supply, did the job!

Now the communication comes up again, even after RS232 was un- and replugged

Upvotes: 0

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