There are two I2C ports on the 40-pin header, I2C0 and I2C1. Both are 3.3v voltage level. You should check your device to make sure which I2C is attached to and what the voltage level is.
What’s the pull-up voltage level? There is 3.3v pull-up inside the module. Did you use a oscilloscope to observe the waveform of I2C data/clk to make sure the communication is correct?
@Trumany
Yes, i can get the waveform of I2C data/clk.
pull-up of ADS1115 is 3.3v (PCA9685 is 3.3v too.)
I2C works very Well. (i tried PCA 9685)
There is problem using ADS1115. (I tried ADS1115 on arduino, no prolem.)