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I bought the official 7" touch screen. In the instructions, I was told to connect the GND and +5V connectors only, even if 4 wires were shipped. So that's what I did until now and things were working fine.

Today I received another 7" touch screen, but it came without a manual, so I looked up the wiring in the Internet and it told me to connect the SCL and SDA pins as well.

What's the benefit of connecting SCL and SDA to the official 7" touch screen? What can I get out of it?

My OS is Raspbian, which detects the screen automatically. I'm using Pi 2 and Pi 3.

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I²C is used for transmitting the touch data.

The full model names of the Pi 2 and Pi 3 are actually Pi 2B and Pi 3B. In those models, the I²C communication can be done through the display adapter. Same applies for the Pi 1 A+ and Pi 1 B+ (with +).

However, on the first editions Pi 1A and Pi 1B (without +), I²C needed to be set up with the separate wiring.

In the linked tutorial, a Pi 2B is used, so it would not have been necessary to connect the additional wires for the I²C bus.

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    Good to know. I wish the installation instructions included this bit of information. I originally had the SCL and SDA pins connected to my Pi 3, which caused intermittent conflicts with the HiFiBerry. Unplugging these pins resolved the conflicts with no apparent effects on the touchscreen. – Carlton Feb 15 '17 at 19:37

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