Datasheet

Connect the i2c SDA data pin to your i2c data pin. On the classic Arduino

Uno/Duemilanove/Diecimila/etc this is Analog pin #4

Unfortunately, the i2c lines on most microcontrollers are fixed so you're going to have to stick with

those pins.

You may be wondering, how is it OK to connect a 3.3V chip like the TSL2561 to 5.0V data pins

like the Arduino? Isn't that bad? Well, in this specific case its OK. I2c uses pullup lines to the

3.3V power pin, so the data is actually being sent at 3.3V. As long as all the sensors/device on

the i2c bus are running on 3.3V power, we're fine. However, don't use a 5.0v powered i2c

device (like the DS1307) with pullups at the same time as a 3.3V device like the TSL2561! If

you want to use this sensor with a datalogger that uses the DS1307, remove any/all of the

pullup resistors from the DS1307 SDA/SCL pins. The pullups built into the TSL2561 will then

be active and keep the voltage at 3.3V which is safe for both the RTC and the sensor.

