I have same problem as several others have reported: I2C seems not to be working correctly. I’m trying to get the pololu MinIMU-9 v2 connected to the primary I2C pin 20/21 to work. Running the sample application from pololu works flawless on an MEGA (github.com/pololu/l3g-arduino). On the DUE something is blocking in the communication and the SDA line is pulled low and left in this state. The MinIMU-9 v2 is 3.3/5 volt compliant (built in level converters) so I don’t thing I is an electrical issue. The strange part is, that the SDA line is permantly held low after the first communication approach, and stays there.
I’m using a 20x4 I2C LCD on SDA1/SCL1 with no problems – apart from the external applied pull up resisters. I don’t have analyzing tools for debugging the I2C so I really don’t know where the communication stops/hangs– only oscilloscope available.
I found another thread with similar issue and (http://forum.arduino.cc/index.php?topic=217442.0
) tried the alternative wire.cpp with no luck. I’m kind of stuck with this problem
Edit - Seems to be hardware related... The 2 x 1.5 Kohm is to low for the pololu MinIMU-9 v2. Must find a way to replace with 4,7 K or higher values. The thing is, that the wire(?) lib stop with SDA line pulled low, and i don't know why. Must bee somthing with ack or similar.....