Hi,
I'm trying to use a RGB color sensor (https://learn.sparkfun.com/tutorials/isl29125-rgb-light-sensor-hookup-guide) with the SDA/SCL pins.
The problem is that I need to connect two sensors with only one arduino. Is it possible to do it, since arduino has only one SDA/SCL connection? How can I do this?
That chip has just one I2C address and it can not be changed.
You could use a multiplexer, there are a number of ways to do that. With a special chip or with a logic chip, or with a mux chip.
Google for: arduino i2c mux
and click also on Images for some examples.
According to the datasheet:
The device identifier bits of ISL29125 are internally hard-wired as "1000100".
I agree with what was said above, however, just for reference, the Arduino Due and the Teensy 3.x boards have 2 I2C busses.
You can use a 74HC4067 to multiplex nicely with the color sensors. Miltiplexing several devices that have the same I2C address is described very well in this document:
The chip is available in a DIP package, which lends itself nicely to breadboarding.