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I've dealt with others here having issues with that MAX485 module. You may need to remove R7 from that MAX485 board (and remove or disable any termination connected to the gas analyzer). Also make sure to connect 3 wires (A, B, and GND) between the MAX485 board and the gas analyzer. Please refer...

What is the specific MAX485 module you're using? Since you mentioned ModScan, I assume you've already tested communicating to the gas analyzer from a computer using a USB to RS-485 adapter and ModScan. Is this correct? I recommend using ModSim (which is a Modbus Slave simulator) on a computer...

If Ethernet communication was previously working, but now it is not, something must have changed. Here are some ideas of things to check/try: Confirm that there is an Ethernet link on both your computer and the AMF controller (there may be an LED on or near the Ethernet jack, and in Windows...

Can you please clarify this statement? Is it the USB communication that was working and is no longer working or was the Ethernet communication previously working?

That video shows two methods - Manual (i.e. Static IP) and Automatic (DHCP). Can you share the exact steps you performed and settings for both the AMF controller and your computer? Do you have an Ethernet cable connected directly from your computer to the AMF controller or are you using an...

Thanks for providing an update on this. I'm glad to hear you got it working properly. This type of scenario is exactly why I encourage taking the extra time to dig into and understand the root cause of an issue before declaring it fixed.

I don't understand this. What is a "connection" when using Modbus RTU? So then what setting in Open ModScan should be increased if you have a Modbus RTU slave that takes a long time before responding to requests and Open ModScan"s requests are timing out?

@SaNNy It seems that the Slave Response Timeout setting in the Modbus Protocol Selections window has no effect (I was only able to test using a serial connection). With no slave devices connected, the Number of Polls counter increments at the rate dictated by only the Scan Rate setting...

I'm able to see both my FTDI-chip USB to RS-485 converters in Open ModScan's connection window. Does Window's Device Manager show your converter under the Ports category? Do you know what type of chip is in the your converter you're using? It's possible Open ModScan is not able to detect your...

Thank you for the explanation. But if you are still powering the RS-485 module from 3.3V instead of the required 5V, then you are using the RS-485 module outside of its specified operating conditions, and therefore, unexpected behavior may occur. I'm not saying this will necessarily solve the...

I would interpret your screenshot as OpenModScan did not find any Modbus devices. Perhaps your computer and the Modbus/ TCP server are on different subnets. I see you're scanning for devices on the 192.168.1.xxx subnet. Is your computer's IP address also on this subnet (i.e. does it start with...

I realized that this comment may lead you to try to power the RS-485 module with 5V, while still using the 3.3V-powered ESP32. Don't do that. According to this guide (https://learn.sparkfun.com/tutorials/esp32-thing-hookup-guide/hardware-overview), the ESP32's I/O pins are NOT 5V tolerant, so...

I believe that RS-485 module requires 5V, so the issue may be caused by powering it using 3.3V instead of the required 5V. Additionally, you really should have 3 wires between the RS-485 module and the inverter (+, -, and ground). Without that 3rd ground wire, the two devices may not share the...

Yep, just one of the many quirks of Modbus. You're not the first to be confused by this, and certainly won't be the last. This "off by one" addressing issue is one of the most common mistakes made when configuring Modbus devices.

Are you sure you're not confusing the scanning status (i.e. what device ID it's currently trying to scan) with the actual discovered devices? In your screenshot, the scanning is 100% complete and the Device Id shows 10 because that was the highest Device Id you configured it to scan, not because...

You must be used to using 0-based addressing. This software appears to use 1-based addressing, just like WinTECH's ModScan. Take a look here for more details: https://control.com/forums/threads/modbus-register-numbering.49844/

Hm...curious. The only explanation I can think of is that one of the wires in the Ethernet cable was either broken, making only intermittent connection, or the wire was not making good contact to the Danfoss device's terminal (for example, only on the insulation, not the conductor). Of course...

I doubt Modbus Poll has any special error handling, nor would any other master. Something else is probably going on here. Just to confirm the root cause, what exactly did you do to resolve the issue? You said you changed the cables, I assume that means you got new cabling. What's different...

I don't think the Delay setting in Home Assistant will make any difference, as it only applies to the very first request sent, and seems to exist more for Modbus/TCP devices than Modbus RTU devices. From the Home Assistant Modbus documentation:

OK, that's good news then. As I said, if both TXD and RXD LEDs are blinking when the Danfoss device is connected, that means communications is 90% working - the request from home assistant is getting to the Danfoss device and the Danfoss device is responding. This means all communication...