jackkitley:
The wires are a live 12V, a ground and a data wire which is 5V.
This is not documented in the manual or website. How did you determine this is the function of each of the three wires?
There are multiple mentions on the web regarding the make and the temperature probe used.
A good few of those where they simply replaced the existing probe with a DS18B20.
Bob.
I use a Saleae logic analyzer, much cheaper then a scope and will decode the protocol for you. Just select one if it does not work try another. Personally I have both, I use the scope to figure out what is happening then the logic analyzer to decode it. A protocol is a standard set of rules that allow electronic devices to communicate with each other. These rules include what type of data may be transmitted, what commands are used to send and receive data, and how data transfers are confirmed. RS232 is the standard defines the electrical characteristics and timing of signals, the meaning of signals, and the physical size and pinout of connectors. To simplify it RS232 is a physical layer standard, a protocol is how the data is processed regardless of how it is physically transferred. This response is to help you get started in solving your problem, not solve it for you.
Good Luck & Have Fun!
Gil
ballscrewbob:
@PerehamaThere are multiple mentions on the web regarding the make and the temperature probe used.
A good few of those where they simply replaced the existing probe with a DS18B20.Bob.
I admit I have not read those articles in detail. The DS18B20 is a digital thermometer.
I was assuming that what the were doing was using the digital device instead of thermocuples to read say the temperature at the Solar Panel or the Geyser. If you look at the diagram that I posted earlier there is unidirectional communications from the Solar Panel to the C Box.
The OP seems to want to replace the Display Unit not just read temperatures. However since people use the DS18B20 the coms to the Display Unit probably operate using 1 wire plus ground in the same way. Though of course the we dont know the message formats used by the Display Unit.
So far I have drawn a blank on getting details of the Display Unit protocol. An answer to @Perehama's question about how the OP knows what the functions of the wires might give a few more clues.
There is a tutorial on using the DS180B20 with the Arduino here;
https://www.youtube.com/watch?v=1GD29sXLOJ0
That is still a long way from replacing the Display Unit though.