Open source PLC Wifi

Question

I'm working on a project that involves a device called the plduino (aka Open Source PLC). This is the website for the device:

https://www.digital-loggers.com/plc.html

and the GitHub:

https://github.com/digitalloggers/PLDuino

Using the examples on the GitHub, I've been able to figure out other parts- storing on the SD card, the GUI, digital IO, etc. But I haven't been able to figure out the WiFi module (which seems to be through a ESP8266 device). I looked through the libraries directory on the GitHub link, but didn't find anything that looked like it connected to the internet or could send or receive data. The documentation says the device can connect to wifi, but is otherwise very little help.

Has anyone used this before? How do I make this device connect to wifi?

Answer 1

This is not particularly easy to figure out. The ESP8266 is addressable via a serial port. The ESP8266 firmware is called NodeMCU, which sits on top of the ESP8266 firmware and allows you write Lua code to implement custom Wifi functions. The PLC comes with example Lua that starts a webserver and publishes a webpage that allows you to check and set the status of the PLC (but only if you connect to the PLC, which is in access point mode.)

If you want it to behave like wifi on a normal desktop computer, you have to do some Lua programming (I could not find any Lua code online that did basic things out of the box, but there are a fair number of examples and snippets on the NodeMCU sites.)

In spite of how cool this device is, I ultimately decided it was just too much work to get the Wifi integration working (the Arduino stuff is of course pretty easy). You also have the problem of how to get your data logs somewhere. Since the data is on the Duino and the ESP8266 is the web interface, you either have to poll the Duino (which the example code does) and upload to a site (e.g. AWS), or log the data on the Duino, then send it over the serial port for upload -- MORE Lua and Duino coding. Plus if you want to put your data on AWS IoT (for example) the Duino/NodeMCU technically does not support the TLS 1.2 and X.509 cert handling you need to register (although they are apparently some workarounds now.) Life. Is. Too. Short. For. That.

I switched to Raspberry Pi, which is about 1000 times simpler, even though it does not have the cool features like open collectors and optical isolators. I'm now looking at Pi enclosures, such as the nice BC packaging from Phoenix Contacts. I decided it was simpler to make my own custom PLC for my home HVAC automation project than it was to code the DL-PLC. Bummer. Maybe they'll do a Pi version of this someday.

The repositories for my DL-PLC and RPi projects are on GitHub (https://github.com/dglcinc/HVAC-plc and https://github.com/dglcinc/HVAC-pi), you may find my Lua code and implementation notes useful if you want to get the wifi working on the DL-PLC. I did get it working in station mode (so you can join it to your home access point, address it with a DHCP IP, etc.) but that's about as far as I got.