I am looking for some advice on how best to implement my project.
I am installing 42 large LED panels on a curving pedestrian bridge about 50 meters long. Each panel will respond to a passerby by changing color and fading back to the original color. This is a public art project in a hospital.
I have coded this project so that each Uno is in charge of one large panel, sensing the person and changing the color in response. While each Uno is independent, it can sense what it's immediate neighbor is doing and respond accordingly, for example if two people approach each other, the panel in the middle can turn a different color than it would normally with a single pedestrian.
I am currently trying to implement a system where all units can respond to the ambient light level on the bridge, for example, to adjust for day and night or changing weather conditions. This is necessary because one side of the bridge is a glass curtain wall exposed to the outside.
My question is about how best to communicate with all the Unos on the bridge. The information transmitted could be as simple as a single bit indicating day or night (as read and processed from a single "light meter" unit in the middle of the bridge), or as complex as an 8-bit light level transmitted to all panels.
To create an I2C network, I would have to use bus extenders due to the distances involved. This complicates my board design somewhat but I could do it if needed. The info to be transmitted could run at a VERY low rate.
I'm just not sure if a single TTL signal transmitted to all 42 units constitutes a "bus" and therefore would require bus extenders just like I2C. If that's the case, then I would just go with I2C and get all the extra capability.
Any advice or experience in a similar situation would be greatly appreciated!