Opta RS485 port not working

Official Hardware Opta
1

Hello,

Bought 2 Opta RS485 units from Conrad.
Tried this example: https://docs.arduino.cc/tutorials/opta/getting-started-with-modbus-rtu?
Made all connections exaclty as shown, including 24 V supply from lab power supply.
Followed instructions exactly, client always logged " ... failed! Connection timed out".
Connected client to osciloscope, no signals visible.

Bought 3th device directly from Arduino. Same result.

Measured between A and ground, between B and ground, A and B, all with and without 330 ohm termination resistor. Nothing works on any of the 3 devices.

Does anyone has an idea what can be wrong?

Patrick

ArduinoIDE
ArduinoIDE1217×1311 120 KB

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1 Like
3

Hello @phacour

I've checked the sketch "Modbus RTU Client Kitchen Sink" from the ArduinoModBus library on the oscilloscope and I can see perfectly the bus.

A - A
GND- GND
B - B

Make sure the GND is connected

Please make sure you have the latest versions of the ArduinoModbus and ArduinoRS485