For one reason and another I've returned to a puzzle that 2 years ago I didn't have time to investigate fully. This time I'm hoping to make more headway, but we'll see how far I get :-)
When we built our house we were required to install and maintain a treatment plant for our waste. In itself this was a saga (for another day) but the result is that we have a treatment plant a short distance from the house that processes all our... waste. It's worked well but it's now a couple of years old and so I'm starting to pay more attention and consider the maintenance that will be required.
Part of the problem is that it's a total black box. It sits there making a few noises and apart from the "red light of doom" on top of the cabinet it has zero external visibility without opening the cabinet. Living in Scotland we're well accustomed to the weather and frankly the chances that this particular system will go wrong on a fine summers day are very remote. When the red light comes on it will likely barely be visible through the rain or snow! Which brings me back to the puzzle...
The controller for the system has a comm port. Oddly it's a 3.5mm audio jack. Not quite what I was expecting.
It's worth mentioning at this point that we have asked the manufacturer whether we can buy a box that will connect and provide us with data, but they're not really targetting individual homes which explains the 4 figure sum they wanted to connect the system to a cloud based monitor with an ongoing fee! :-( They also don't seem willing or able to provide any details about the comm port.
The simple reason I'm interested is to monitor the system from the warmth of the house :-) We have a very useful Home Assistant setup that we are slowly expanding and adding the treatment system to it seems like an obvious step. Of course, adding it means we need access to the data :-)
When I last looked I went as far as getting a 3.5mm connector with outputs that I could connect to and ran a cable to the nearby data cabinet. So I have 4 outputs from the port.
Obviously at this point I have no idea what the outputs are (no docs appear to exist online for the controller at this level of detail). As there are 4 and the devices that are sold that connect appear to use a DB9 serial port connector on the other end, I am tempted to think they will be a VCC, GND, RX and TX?
I have found that one connection is a steady 5V and one is a steady GND, so it may be that I am on the right lines? I'm hoping a logic analyser will arrive tomorrow which will no doubt lead me down another rabbit hole... :-)
As this is all new territory for me any thoughts or suggestions are welcome :-)