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I am trying to control a RS-485 RTU device (Love 16C-3) using a Python script (pymodbus library) that runs on a Windows 10 PC. The hardware is connected to the computer using a USB-RS232 cable.

In my initial test, the Python script is not able to read anything off the RS-485 device.

  1. What is the RS-485 pin out for the DB9 connector?
  2. Should a USB-RS485 cable be used instead?
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1 Answer 1

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RS-232 is RS-232, RS-485 is RS-485. They are mutually incompatible on the electrical layer, they use different voltages and signalling. You need a USB to RS-485 cable first.

There are no RS-485 signals (A and B) on a DB-9 in a USB to RS-232 cable.

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