LIDAR lite and Beaglebone Black I2C signals

In my previous post about the LIDAR lite I said its I2C signals were 5V. Well, if you go to their new support page you can check in this FAQ that I was wrong. They are 3.3V.

If you connect 5V to any of the 3.3V pins of the Beaglebone you will probably kill it so just to make sure I power up my Rigol scope (I got it after listening to this eevblog review, thanks Dave;-) and check the voltage on one of the I2C pins of the LIDAR lite. Humm… in the unconnected pin I have 3.6V. A little higher then 3.3V. Lets check the Beaglebone absolute maximum ratings. I’m using the I2C2 pins (connector P9, pins 19 and 20). From the Beaglebone electronic diagram they go into the TI AM3358 processor. In the AM3358 datasheet I see that the maximum voltage is 3.8V… we are pretty close to the maximum but it should be ok. This is the processor chip so we need to be careful! If I measure the voltage on the I2C2 Beaglebone side (unconnected pins) I get 3.2V.

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