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Author Topic: RS485 to RS422 connection  (Read 153 times)

PLCwannabe

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RS485 to RS422 connection
« on: November 21, 2022, 11:40:53 AM »
I'm trying to set up a serial connection between an APX scale display (4 channel display) and BRX. The APX Display has 3 comm connections, 1 & 2 are for RS232 and comm 3 is for RS422/485. Comm 3 has a 5 pin connector, with terminals marked as RxA,RxB,TxA,TxB and Grnd. What is the correct way to connect this to the BRX onboard serial 3 pin connectors? I have tried many different combinations but none have worked.

Concerning the rs232 comm ports, I have used a streamin instruction to read the scale display values, which works well. But it only streams in 1 channel value, and I need to read all 4 channels. Can rs232 be used to poll the APX for all the values at once with a MRX instructrion? Does rs232 also use a slave id? (I can't find any config settings on the APX for master/slave or for id/address).

franji1

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Re: RS485 to RS422 connection
« Reply #1 on: November 21, 2022, 01:12:49 PM »
Can you provide a link to a manual?  The pdf was just a "spec" sheet.

The on-board serial port on BRX MPUs are RS-232 only.  You would need to purchase one of the BX-P serial POMs or a BX-SERIO module to get 422/485.  Not sure if RS-232 is an option for you.

EDIT - SORRY you CAN do RS-485 half-duplex with 3 pins (differential pair).  However, I have no clue about the wiring on the scale side.
« Last Edit: November 21, 2022, 03:23:30 PM by franji1 »