ESP8266 Community Forum

- Tue Jul 18, 2017 7:29 am #68308

How do you plan on adding it to the ESP8266? Are you going to build a board for it?

Indeed. ESP12E/F module with various peripherals; now for client I have to add this RS485 communication.

Using a separate module is not my ideal solution; I prefer to have everything on board as much as possible. The part that makes me most uncomfortable here is that I can hardly do any testing before going for PCB prototype production. As it's all digital it's basically a matter of carefully reading (and re-reading, and double checking) the connections based on the data sheets, and it should work. That's the upside.

R74 what value should that one have?

You would not be using the 3.3 volts on the RS485 side connection.

What do you mean with this? Different voltage needed? I have 5V and 12V available.

- Tue Jul 18, 2017 7:50 am #68311

The part that makes me most uncomfortable here is that I can hardly do any testing before going for PCB prototype production.

What makes me uncomfortable is you wanting to go into production after asking these questions. I recommend you have someone with experience look over your design first. And I mean all aspects.

Typically a 120 Ohm termination resistance is used at the end of each line. But on short lines it isn't as necessary. I would use 220 Ohms. The two 470 and the 220 would be close enough to 120.

You don't need to send power to the other device. Just the two serial lines and a common/ground connection.

- Tue Jul 18, 2017 8:00 am #68312 Prototype only; and not want to but have to. Going to try and get my hands on some of the MAX3485 chips to do some proper tests.
It's a modification of an existing system of which I have already working prototypes; suddenly the need for this kind of communication as it's to be built into a fridge. Normally using WiFi for communication. So it's not that bad, it's just that I've never had to touch RS485 communication.

- Tue Jul 18, 2017 1:06 pm #68323 So if you are building a data interface into the fridge end, is it defined how this should be interrogated from outside over the RS485?

If you have freedom of choice then it might be worth considering a standard like MODBUS which is commonly used for things like this.

There are also MODBUS libraries for Arduino / ESP8266. E.g. https://github.com/andresarmento/modbus-esp8266