Sorry if this is the wrong forum but I don't see a forum for the Atmel START.
Using Atmel START and Atmel Studio 7 to create an I2C project for the ATSAMD21G18 (Adafruit Feather M0). I created a simple project with only Delay and I2C drivers selected on START. When I build the resultant project in Studio (without ANY modifications) I get a warning "Requested I2C baudrate too low, please check". I had selected the speed at 400KHz in START. The resulting speed is verrrrry slow! Using i2c_m_sync_set_baudrate to change the speed (after disabling the hardware and re-enabling) seems to have no effect.