I'm running raspbian on my pi and followed this tutorial to get the i2c going. i2cdetect -y 1 used to detect my i2c devices but doesn't anymore. The sensor is connected like this:
Could this be a software issue?
Just to make sure,
You have connected VCC to 5v, SDA to SDA, SCL to SCL and GND to GN.
First of all, what do you see when you type
i2cdetect -y 1 (assuming you have 2nd version of Raspberry Pi, else type
i2cdetect -y 0) ?
Do you see an empty address i2c table ?
If yes, then, According to the documentation here
"There are two operating modes for the SRF02. I2C mode and Serial Mode. This is set with the Mode pin, connected to 0v Ground for Serial Mode and left unconnected (or tied to +5v Vcc) for I2C Mode. "
Have you tried to connect the mode pin to +5volts yet ?
All the device not work directly on raspberry pi I2c bus without change, maybe you can try to add/remove the pull-up resistor.
Are you sure the device is adapted to raspberry pi spec ?
sometime you need to remove the pull-up resistor from the device (if you device is for arduino) because the raspberry have pull-up (1k8) integrated and the arduino not.