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So I would not run low level MCU GPIO level signals over the cable wires. In this example, the QScreen Controller selects the serial A/D by outputting a LOW signal on /SS. The SPI can transfer data much more rapidly than an asynchronous serial link - its maximum rate is 2 Megabits/second. UART transmitted data is organized into packets. If one or the other end fail to see the heartbeat packets come or get acknowledgement of them then know that your cable is either disconnected or has broken wires. So take advantage of that and let your systems MCUs implement heart beat handshaking directly though the RS485 communications layer using appropriately designed small packets. Cable jacket: Made from high-quality PVC, the outermost jacket layer has high elasticity, helping to protect the cable from strong environmental impacts. There is a huge benefit of the RS-485 electrical layer protocol that allows for long distance communications in the presence of multiple volts of common mode voltage differences between the two ends. In this tutorial, we are going to learn about the RS485 communication protocol and how to implement it with the two Arduino Nano we have with us and how to use the MAX485 RS485 to UART conversion Module.

I recently bought some RS485 cable, it had two pairs, both had stripes. The device ships with an Ethernet RS-485 communication interface as well as a RS-485 to USB cable, which is said to be able to communicate with a PC using proprietary Windows based software (and driver, I think). But I notice that he describes using a (different) RS-485 to USB converter and splicing from the Ethernet cable to the converter, rather than using the converter cable that ships with the charge controller. What company makes the driver for the RS485 converter? 2 Alphanumeric LCD, and MAX485 UART to RS485 converter IC connected to each end of an Ethernet Cat-6E cable via an RJ45 connector. Simply using the provided USB converter cable is not working for me right now with the Pi. Is it necessary to do the ethernet cable splicing as indicated in the above link, or should I simply be able to use the provided USB cable? Note that this Hackster project does something similar with splicing an ethernet cable to a UART breakout module. The mention of "Ethernet RS-485 communication interface" confused me. You might make it work anyway, with a bit of stuffing at the protocol level, or it might "just work" with sparse communication and a receiver that interprets 0V differential as idle.

The RS485 protocol uses differential data signals for improved noise immunity; thus RS485 can communicate over greater distances than RS232. This way, the lines will be biased to known voltages and nodes will not interpret the noise from undriven lines as actual data; without biasing resistors, the data lines float in such a way that electrical noise sensitivity is greatest when all device stations are silent or unpowered. For these secondary devices you have to implement your periodic heart beat check in some device specific way. The only way this would not work is if the secondary device only takes "write only to device" transmissions with no possibility of any acknowledgement or return result. A PoE device needs to accept both variations in either polarity (4 possibilities) to be fully standards-compliant, in addition to the signalling that a standards-compliant source requires to enable the power on that port. If an existing standard has some value to you, then you might have a look at PoE. A ground connection is also necessary to ensure that the communicating devices have a common voltage reference. RS232 is by far the most common protocol.

The far better situation is to realize that connected cables enable communications and disconnected cables impede communications. For devices where you have to consider the devices at the far end of your cables to be unable to be modified, either hardware or software wise, you have to get clever regarding how you determine if the device is connected. This can vary greatly depending upon the device. To make sure that your USB to RS-485 cable & the device RS-485 port are working, have you tried using them with a Windows PC and the manufacturer's s/w? No I have not been able to test this using the Windows software. Signal High and Lows are measured against the GND level so shifting the GND level will have a disastrous effect on the data transfer. Is it likely that the shipped cable is configured differently or do I simply have no way of knowing that (short of dissecting the cable)? One uses the data lines for 10/100 Ethernet, so that there are still 2 unused pairs in that cable.