RS485 Communication Problems

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drmartin
Posts: 2
Joined: Tue Jul 09, 2024 8:57 pm

RS485 Communication Problems

Post by drmartin » Tue Jul 16, 2024 9:13 pm

I’m running v1.0.3 of the controller software on a version 15 main board. The VFD is a H100-3.7S2-1B made by Huajiang. It uses the same Modbus addresses and values as the H100 on the Tool Configuration window. I’ve verified this by using a Waveshare USB to RS485 adapter and Modbus master software and reading and writing to the various addresses. When the Buildbotics controller is connected to the VFD and correctly configured the status connection indicates “CRC error” most of the time with an occasional “OK”. If I send M03, M04, M05, or S commands from the MDI screen sometimes it works but most of the time it doesn’t. If I configure the USB to RS485 as a Modbus slave and connect it to the Buildbotics controller this is the data I see in the slave software log.

>4:36:25 PM: RX: 7f 3e 3f fe
>4:36:25 PM: RX: 7f 3e 3f fe fe de 6c fe
>4:36:25 PM: RX: 7f 3e 3f fe fe de 6c fe
>4:36:25 PM: RX: 7f 3e 3f fe fe de 6c fe
>4:36:25 PM: RX: 7f 3e 3f fe fe de 6c fe
>4:36:25 PM: RX: fa f2 fe ea fe fa ae a4 fe
>4:36:25 PM: RX: 7f 7e ea fe fa ae a4 fe
>4:36:25 PM: RX: 7f 7e ea fe fa ae a4 fe
>4:36:26 PM: RX: 7f 7e ea fe fa ae a4 fe
>4:36:26 PM: RX: 01 03 00 05 00 01 94 0b
>4:36:26 PM: Sent data: Function code:3.
>4:36:26 PM: TX: 01 03 02 01 90 b9 b8
>4:36:26 PM: RX: 01 06 02 00 00 00 88 72
>4:36:26 PM: Received address is not within viewable range, Received address:512.
>4:36:26 PM: TX: 01 06 02 00 00 00 88 72
>4:36:26 PM: RX: 01
>4:36:26 PM: RX: 01 06 02 00 00 00 88 72
>4:36:26 PM: RX: 01 06 02 00 00 00 88 72
>4:36:26 PM: Received address is not within viewable range, Received address:512.
>4:36:26 PM: TX: 01 06 02 00 00 00 88 72
>4:36:26 PM: RX: 7f 3e 3f fe fe de fe
>4:36:26 PM: RX: 7f 3e 3f fe fe de 6c fe
>4:36:26 PM: RX: 7f 3e 3f fe fe de 6c fe
>4:36:27 PM: RX: 7f 3e 3f fe fe de 6c fe
>4:36:27 PM: RX: 7f 3e 3f fe fe de 6c fe
>4:36:27 PM: RX: fa f2 fe ea fe fa ae a4 fe
>4:36:27 PM: RX: 7f 7e ea fe fa ae a4 fe
>4:36:27 PM: RX: 7f 7e ea fe fa ae a4 fe
>4:36:27 PM: RX: 7f 7e ea fe fa ae a4 fe
>4:36:27 PM: RX: c0 60 05 00 01 94 0b
>4:36:27 PM: RX: 01 03 00 05 00 01 94 0b
>4:36:27 PM: Sent data: Function code:3.
>4:36:27 PM: TX: 01 03 02 01 90 b9 b8

I’m seeing good 03 reads and 06 writes to slave ID 01 but I’m also seeing a lot of extra junk. I’m using about 2 feet of the green pair of a cat 5e cable. I’ve tried adding a 100ohm termination resistor and using a longer cable. I've also tried changing the baud, parity, and bus id settings.

Any thoughts on what might be causing it or other things to check?
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Doug
Posts: 364
Joined: Fri Feb 02, 2018 4:56 pm

Re: RS485 Communication Problems

Post by Doug » Wed Jul 17, 2024 3:33 pm

Try reversing the RS-485 pair.
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drmartin
Posts: 2
Joined: Tue Jul 09, 2024 8:57 pm

Re: RS485 Communication Problems

Post by drmartin » Wed Jul 17, 2024 5:45 pm

That fixed it. Thanks Doug.
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