In recent time I came across situations where RS485 ports caused lots of problems. The ports basically “burnt down” due to severe EM surges in industrial environment. As a work-around we used to bring in the systems from the site to our repair workshop, repair the device and then re-installed it on the client site. The equipment was expensive and we could not keep many drop-in replacements for that. Then what we did was to add a small hardware which basically translated the RS485 data into TCP/IP over Ethernet. The results were exceptional. This not only completely eliminated the damages due to surges but also reduced the customer annoyance, the logistic and support expanses we faced every time we received a May-day call. So, why should we replace or phase out the RS485 systems with Ethernet:
- Better isolation and hence no burning cases, this reduces cost
- Ethernet is faster
- Ethernet may provide different logical channels on the same physical medium like in one device, I used two TCP ports on same IP. One port for RS485 communication while the other one for digital triggers. This completely eliminated the “muddling” issue of two different data sources while using single physical Ethernet port.
- Much better stack structure in Ethernet as you have lots of options like TCP client, server, HTTP server, SNMP etc. according to requirement.
- Easier and smoother integration with existing TCP/IP-based network like local LAN.
Currently there are low-cost microcontrollers with built-in Ethernet controllers options like those offered by Microchip, TI and many others. This has eroded the myth of cost effectiveness of RS485 over Ethernet. Infact, keeping in view the running cost of both systems, Ethernet is much cheaper than RS485. Therefore, while designing a new system, Ethernet should be preferred over RS485 and if RS485 is already installed, low-cost converters can be used to transport data over Ethernet.