I use a KW41Z board as a master and a LTC3207 LED driver as a slave device and try to set up a communication between this devices. I have checked the accelerometer example and it was relatively simple, now I use almost the same code with some modifications as changing I2C1 bus to I2C0, setting up SDA/SCL ports (I use pull-down resistor in my ports configuration in this case), addresses, etc. The SDA/SCL lines are both connected to the voltage source with two ~10k ohm resistors for each connection. No matter what I send, the ack bit is always received, even if the I2C lines are only connected to the board ports and to the voltage source. What can be possibly wrong? I had the same issue with setting up some digital temperature sensor working on One Wire protocol by using GPIO ports.