i2cdetect? http://www.lm-sensors.org/wiki/man/i2cdetect http://www.lm-sensors.org/wiki/man/i2cdetect Both the web page and the program itself will inform you

i2cdetect? http://www.lm-sensors.org/wiki/man/i2cdetect http://www.lm-sensors.org/wiki/man/i2cdetect Both the web page and the program itself will inform you that running it could cause Armageddon, but assuming all you have plugged into your i2c bus is an LCD it really shouldn't cause any harm. On Raspbian, you'll have to apt-get install i2c-tools to install this (and you'll have to modprobe in the i2c drivers as described in my blog post). On the Adafruit distro it comes pre-installed. Running i2cdetect on my Pi which currently has one of those LED matrix devices I talked about in the blog results in this: pi@raspberrypi ~ $ sudo i2cdetect 1 WARNING! This program can confuse your I2C bus, cause data loss and worse! I will probe file /dev/i2c-1. I will probe address range 0x03-0x77. Continue? [Y/n] y 0 1 2 3 4 5 6 7 8 9 a b c d e f 00: -- -- -- -- -- -- -- -- -- -- -- -- -- 10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 70: 70 -- -- -- -- -- -- -- (Telling me it detected a device at 0x70, which is correct for this device). I don't have the LCD you have so I'm not sure if it is properly detected by i2cdetect, but that's what I'd try first.