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I am working on a project that involves a Solar Charge Controller. 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).

What I want to be able to do is to communicate (or at least read from) the charge controller from a Raspberry Pi.

This person has proved that it can be done (see link). 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.

Simply using the provided USB converter cable is not working for me right now with the Pi.


So my question(s):

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?

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)?


Note that this Hackster project does something similar with splicing an ethernet cable to a UART breakout module.

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  • \$\begingroup\$ What company makes the driver for the RS485 converter? \$\endgroup\$ – Voltage Spike Oct 1 at 17:42
  • \$\begingroup\$ as far as I can tell, it is the manufacturer of the solar charge controller, EPEVER, that makes the converter \$\endgroup\$ – Eric Czajkowski Oct 1 at 18:03
  • \$\begingroup\$ @EricCzajkowski - Welcome to the site :-) (a) The mention of "Ethernet RS-485 communication interface" confused me. After looking at all your links, I do not believe there is an actual Ethernet interface at all. RJ45 =/= Ethernet. I know RJ45-RJ45 cables are often colloquially referred to as Ethernet cables, but that isn't their only use. They are often used for serial connections going to a terminal server in datacentres, for example. (b) 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? \$\endgroup\$ – SamGibson Oct 1 at 19:19
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    \$\begingroup\$ @SamGibson Thanks for that clarification. No I have not been able to test this using the Windows software. I may need to try to that just to prove that this works at a minimum. \$\endgroup\$ – Eric Czajkowski Oct 2 at 20:08
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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?

If you can find drivers for the R Pi then you can use the converter. I'd start by finding out what chip is in the propriety RS485 to USB, they might have a linux driver.

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)?

You will need a pinout and find the voltage, if you have an oscilloscope, it should be easy to find the pins that carry the RS485 and if they are using any additional pins for signaling (some RS485 converters also have GPIO's). By the looks of the webpage, they are only using the two differential pins and you could use any RS485 converter that is compatible with the voltage (which is probably 5V or 3.3V). Make sure the RS485 converter is compatable and find the two data pins and you should be able to roll your own.

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  • \$\begingroup\$ The software and driver provided by the mfr. all appears to be Windows-centric. \$\endgroup\$ – Eric Czajkowski Oct 1 at 18:04
  • \$\begingroup\$ There is already a Raspberry Pi project on GitHub to use another USB to RS485 adapter that already has a linux driver, due to original cable (which uses EXAR chipset) had some driver issues. \$\endgroup\$ – Justme Oct 1 at 20:08
  • \$\begingroup\$ @Justme do you have a link for the GitHub project? \$\endgroup\$ – Eric Czajkowski Oct 2 at 20:09
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Here is what I have gathered here from the answers, comments, and some additional research:

1) The cable that shipped with the device should work for my purposes. However, I will need to be able to install the correct driver(s). Upon further research, I was able to figure out that the device manufacturer downloads include a Windows installer for this XR21V1410 chip, which seems to have Linux drivers available.

2) The two converter USBs are indeed configured differently in that they use different chips, which require different drivers.

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