on the ' OpenI2C(MASTER, SLEW_OFF) ' function, MASTER must be 0x8000 ( I2C module enabled)
and SLEW_OFF must be the Baud Rate Generator (I2CxBRG), which is I2CxBRG = (FCY/FSCL – FCY/10,000,000) – 1
If you refer to your processor's datasheet, BRG is explained in the I2c section .
Correction:-
Actually, for the dsPIC30F4011 processor;
I2CBRG = (FCY/FSCL – FCY/1,111,111) – 1 (just referred to your processor datasheet)
and MASTER must be 0xFFFF