Is it possible to create a RS485 bridge over Wifi using 2 ESP07's

Question

I've got a solar energy inverter that has a RS485 port for connecting a meter. You can place a separate energy meter in your distribution panel at home, that measures things like power usage, purchase and return of electricity. A two-core cable connects the meter output pins A and B to the RS485 port on the inverter.

A lot of meters on the market have the same protocol, not meaning it's just RS485 for transport but also the Modbus "format" of the data sent by the meter is understandable by the inverter. I tested this provisionally with a meter that's recommended by the inverter manufacturer, and it works. The problem is that the meter can only be connected to the inverter with a wire. There are no wireless options. I want to create a solution for transporting data from the meter to the inverter wirelessly.

My idea is as follows:

At the meter's RS485 connection pins, I just connect them to ESP07 input pins. The ESP07 should read the meter's data and send it over Wifi to another ESP at the inverter side. The ESP at the inverter receives the data over Wifi and generates an RS485 signal on two output pins that are connected to the inverter's RS485 port. In simple terms: a wireless RS485 bridge over Wifi. I cannot find a lot of resources on the internet about creating this by yourself. What I read somewhere is that there's a problem because RS485 is synchronous (think about baud rate), and Wifi is asynchronous.

What I'm thinking is that the ESP07 at inverter just independently generates a new RS485 signal based on the data it receives over Wifi. It acts like it's the meter. The only thing is that there could be an overall delay. Am I thinking correctly?

• Matt: Yes, that's possible. But you'll need both software and hardware, not only mcu chip, but also rs485 converter. Consider that on many occasions wired connection might be simpler, cheaper and more reliable.
• user2190492: Indeed I find internet sources speaking about specific hardware like a RS485 converter that is connected to the ESP. But I don't understand why you need specific hardware for this. In theory the signal is a voltage you can get as input to the pins on the ESP, in your software you can interpret the inputsignals on the pins?
• Matt: rs485 uses relatively high voltage levels, so, no, you can't. If you really wonder you can just grab and read datasheet (e.g. max485) to see what it does and why you can't connect directly.
• st2000: RS485 is 1 of many old standards meant to do different things. RS485 supports multiple drops over 1000+ meters of balanced pair wires designed for electrical noise rejection. Under known / well-understood circumstances, you could probably hack together something simple to allow the ESP processor to listen / decode the RS485 signal. But why take that chance when real RS485 interfaces are cheap & plentiful. Note, you should never (unless specifications state differently) drive a processor input higher then the processor's supply rail. Doing so may lock up or damage the processor.
• tepalia: You'll need RS485 to UART conversion modules on both the sender and receiver ESP07 units. dfrobot.com/product-2392.html