I2C Interface is not working on STNRG388A
We need to configure STNRG388A registers for using Pin 17(SDA) &amp; Pin 18(SCL) as I2C lines.
This can be done using the below code in I2C_Init()

//define SDA, SCL outputs, HiZ, Open drain, Fast
GPIO_Init(GPIO1, GPIO_PIN_6, GPIO_MODE_OUT_PP_HIGH_FAST); // Pin 17
GPIO_Init(GPIO1, GPIO_PIN_7, GPIO_MODE_OUT_PP_HIGH_FAST); // Pin 18
MSC-&gt;IDXADD = ((u8)0x13);
MSC-&gt;IDXDAT = ((u8)MSC_IOMXP2_SEL_P54 &amp; (u8)0x20);


Below line should be added in stlux385.h

#define MSC_IOMXP2_SEL_P54      ((u8)0x30) /*!&lt; Port2[5:4] I/O multiplexing scheme */