USB ↔ RS485 Serial Converter

• 1: GmM USB RS485 Converter
• 2: MCS-83F USB RS485 Converter

1 - GmM USB RS485 Converter

This module provides an 1 Channel USB to RS485 Converter.

It’s one of the most common designs, sold under various different brands.

It is very convenient to use, and works quite well despite being based on a fake FT232RL chip. Seems to run reliable up to 115200 bps. But the bias and termination resistors can’t get disabled (unless removed completely), so there should only be one of those modules on any bus, either at the beginning or the end.

That being said, those modules communicate well with various RS485 and Modbus RTU based devices like power meters or solar inverters. Some use cases might require the use of an additional USB isolator though, as there is none build-in.

The 4 jumpers in the middle of the board bridge GND, TX, RX and +5V from the USB-Serial side to the RS485 one. By removing those, and connecting to the pins directly, the module can work either as a pure USB ↔ TTL serial converter, or a TTL ↔ RS485 converter.

Pros

• PCB and components seem to be good quality, works flawlessly
• USB Type B Socket, Plug-in Screw Terminals and its compact board design make it a perfect choice for DIN Rail mounting
• Very decent price-performance ratio

Cons

• FAKE FT232RL chip (Serial A50285BI)
• Not possible to disable the 120 Ω termination or the 4.7 KΩ A&B bias resistors

General Overview / Specs

Further Information

• https://www.edn.com/usb-to-rs-485-dmx-first-look/
• https://www.voltlog.com/identifying-replacing-a-fake-ftdi-ft232r-chip-voltlog-314/
• https://www.youtube.com/watch?v=1GE-gKgHxZI

Availability / Order

AliExpress

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Case / Mounting / DIN-Rail

3D Printed Case

I’ve designed a DIN-Rail mountable case for this board, it will soon be available on eBay.de

As most of my cases for electronic devices, it has been printed using insulating and flame-retardant (UL 94 HB) DuraPro ABS filament from Extrudr.

STL Files for 3D Printing

The .stl files for the DIN-Rail case are available on Cults3D.com

2 - MCS-83F USB RS485 Converter

This module provides an 1 Channel USB to RS485 Converter.

It is very convenient to use, and works quite well despite being based on a fake FT232RL chip. Seems to run reliable up to 115200 bps.

That being said, those modules communicate well with various RS485 and Modbus RTU based devices like power meters or solar inverters.

Pros

• PCB and components seem to be good quality, works flawlessly
• USB Type B Socket, Plug-in Screw Terminals and its compact board design make it a perfect choice for DIN Rail mounting
• Decent price-performance ratio

Cons

• FAKE FT232RL chip (Serial A50285BI)

General Overview / Specs

Availability / Order

AliExpress

• https://s.click.aliexpress.com/e/_c4NVBZoL
• https://s.click.aliexpress.com/e/_c4Lz7Job
• https://s.click.aliexpress.com/e/_c3b7wDCb
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• https://s.click.aliexpress.com/e/_c3PQdjkF