I am trying to decode the communications protocol between a minisplit indoor unit and the outdoor unit. As described in this thread: Reddit - The heart of the internet
It is using a 0-60V serial signal centered around 30V — the outdoor control board keeps the signal at 30V and the indoor unit pulls it low to 0V to send the data. For replies the outdoor unit pulls the signal high to 60V.
The logic analyser was able to decode the serial signal when set to LSB byte order, 1200 baud rate, 8 data bits, 1 stop bit and even parity.
Before I attempt to build a circuit to turn that into something an Arduino could read, does this protocol sound at all familiar? Is there an existing component that could read it ?
0 to 60VDC 1200 baud rate, 8-bit data, and 1-stop bit is a fairly common method, but the actual data is proprietary. The obvious way to decode is to change settings on the A/C and record the data. Eventually, with enough data points, say 60, 61, 62, 63, etc up to 70 degrees might allow you to decode all the data.
To be clear, I’m only concerned with the physical layer – how to get this into and out of the serial pins on the Arduino. Once I get it into bytes I know how to deal with it.
So now that we know you are really asking about is
the answer is copper wires called dupont for testing but you will likely use some sort of perfboard and solder headers to it to insert the arduino and use something like a screw header for the permanent wiring.
If I connect 60V directly to the Arduino it will release all the internal smoke and stop working!
I need something to convert the level to something the Arduino can handle. I know how to build a circuit to do that, I’m wondering if this is a known format where I can buy a level converter on Amazon for a few bucks rather than design it myself.
I have not heard of a level converter for that voltage, but a voltage divider should work. I am sure there are on-line calculators to choose the resistors needed to get 5V when the peak is 60V. The opto couple mentioned in post 7 is also a great idea if you can find a 60/5 arrangement.
Maybe it would help if I distinguished between a circuit and a device. A circuit is a road map for building something. A device is a circuit that someone else has built.
I want to buy a device. For other serial hardware protocols, it’s very easy to buy a pre-made device that converts the signal to Arduino logic levels. I can go on Amazon and buy a RS-232 or RS-485 adapter, in bulk they might be a dollar each — far cheaper than I could build something myself.
So my question is, is this protocol an established one? Something with an RS- number? Does anyone recognize it? Or is it something proprietary the manufacturer came up with? If it’s the latter I will have to design my own circuit and build my own device. I’d rather skip that step if possible.
All the “RS” standards were developed by Bell Labs as standards for non-Bell equipment to be connected to telephone company communications equipment. The “RS” means recommended standard. Since the Bell labs went away a generation ago, there are no new electrical standards for telephone equipment.
