I’m also looking at doing more general-purpose data transfer rather than the usual “set register X to value Y” or “read register Z” uses that are typical. That said, my intent is to use it for under-table applications with bus lengths of around 1 meter (3’) or less, which appears to be practical, although I need to do some testing to quantify that. Even the simple serial control busses will be superior to I2C in terms of noise immunity and signal reliability, which translates into usable maximum length. Although it may be used to connect several related devices that are in close proximity together, it is not a substitute for a Layout Control Bus like LocoNet or LCC. It was intended to be short and very carefully specified. The key point to keep in mind is that I2C was not designed as a long general-use bus. I prefer to err on the side of caution and reliability. You may be able to work with longer bus lengths or different-sized resistors in practice, if conditions are right. But I’ll try to stick to fairly conservative specifications and the formal standards as much as possible.

You can probably find a source to contradict any statement on this page. There is a great deal written about I2C, much of it conflicting.

There are a number of additional features and characteristics of I2C I’m not covering here, as they don’t seem to be applicable to this kind of use. This page is focused on using I2C between computing devices like the Arduino, and for model railroad applications, although much of the basic information applies to any use of I2C. It is also called the Two-Wire Interface, or TWI, although that’s something of a misnomer as more wires are required if you count the shared ground. The I2C bus (formally written with a superscript, as I 2C) is a short-distance serial bus designed for use on a circuit board, but it can also be used between two (or more) closely-spaced microcontroller systems, such as Arduinos, with some care.

Wire library set i2c clock speed