I2C implementation on Nuvoton N76E003

Question

I am trying to interface MCP23017 I2C based GPIO expander with nuvoton N76E003 microcontroller. I am developing in Keil C51.

Taking the reference of the given examples and some references online, I made a code to control the MCP23017's functions. However, I am not getting any response on the I2C bus. I am attaching my code with this. I am commented the code so it will be easier to understand.

I would be very glad for all your positive comments and criticism. Thanks. Sarth

#include "N76E003.h"
#include "Common.h"
#include "Delay.h"
#include "SFR_Macro.h"
#include "Function_define.h"

#define regular_I2C_pins              0
#define alternate_I2C_pins            1


#define regular_I2C_GPIOs()           do{P13_OpenDrain_Mode; P14_OpenDrain_Mode; clr_I2CPX;}while(0)

#define alternative_I2C_GPIOs()       do{P02_OpenDrain_Mode; P16_OpenDrain_Mode; set_I2CPX;}while(0)

#define I2C_GPIO_Init(mode)           do{if(mode != 0){alternative_I2C_GPIOs();}else{regular_I2C_GPIOs();}}while(0)

#define I2C_CLOCK               0x27
#define MCP23017_SLA            0x20
#define MCP23017_WR             0
#define MCP23017_RD             1
#define ERROR_CODE              0x78

void Init_I2C(void)
{
    I2C_GPIO_Init(regular_I2C_pins);
    I2CLK = I2C_CLOCK; //Set I2C clock rate
    set_I2CEN;         //Enable I2C hardware                          
}

void I2C_Error(void)
{
     while (1);    
}
void I2C_Process(void)
{
    /* Step1 */
    set_STA;                          /* Send Start bit to I2C device */
    clr_SI;
    while (!SI);                      //Check SI set or not
    if (I2STAT != 0x08)               //Check status value after every step
        I2C_Error();

    /* Step2 */
    clr_STA;                                    //STA=0
    I2DAT = (MCP23017_SLA | MCP23017_WR);
    clr_SI;
    while (!SI);                                //Check SI set or not
    if (I2STAT != 0x18)              
        I2C_Error();

    /* Step3 */
    I2DAT = 0x00;                               //address high for I2C EEPROM
    clr_SI;
    while (!SI);                                //Check SI set or not
    if (I2STAT != 0x28)              
        I2C_Error();

    /* Step4 */
    I2DAT = 0x00;                               //address low for I2C EEPROM
    clr_SI;
    while (!SI);                                //Check SI set or not
    if (I2STAT != 0x28)              
        I2C_Error();

    /* Step5 */
    I2DAT = (0x00);                             // Write to IODIRA register to declare port pins as output
    clr_SI;
    while (!SI);
    if (I2STAT != 0x18)
        I2C_Error();

    I2DAT = (0x00);                             // Declare the pins as outputs
    clr_SI;
    while (!SI);
    if (I2STAT != 0x18)
        I2C_Error();

     I2DAT = (0x00);                             // Write to IODIRB register to declare port pins as output
    clr_SI;
    while (!SI);
    if (I2STAT != 0x18)
        I2C_Error();

    I2DAT = (0x00);                             // Declare the pins as outputs
    clr_SI;
    while (!SI);
    if (I2STAT != 0x18)
        I2C_Error();

    I2DAT = (0x12);                             // Address port A
    clr_SI;
    while (!SI);
    if (I2STAT != 0x18)
        I2C_Error();

    I2DAT = (0xFF);                             // Make port A pins high
    clr_SI;
    while (!SI);
    if (I2STAT != 0x18)
        I2C_Error();

    I2DAT = (0x13);                             // Address port B
    clr_SI;
    while (!SI);
    if (I2STAT != 0x18)
        I2C_Error();

    I2DAT = (0xFF);                             // Make port B pins high
    clr_SI;
    while (!SI);
    if (I2STAT != 0x18)
        I2C_Error();

    /* Step6 */
    do{
        set_STO;
        clr_SI;

        set_STA;                   //Check if no ACK is returned by MCP23017
        clr_SI;
        while (!SI);              //Check SI set or not
        if (I2STAT != 0x08)       //Check status value after every step
            I2C_Error();

        clr_STA;
        I2DAT = (MCP23017_SLA | MCP23017_WR);
        clr_SI;
        while (!SI);                            //Check SI set or not
    }while (I2STAT != 0x18);

    /* Step7 */
    set_STO;
    clr_SI;
    while (STO);                                /* Check STOP signal */
}

void main(void)
{
    //Set_All_GPIO_Quasi_Mode;  
    Init_I2C();                                 //initial I2C circuit
    I2C_Process();                         
    while (1);
}

Answer 1

Check your slave address. It should be according to datasheet, page 15:

I2DAT = (((MCP23017_SLA | (A2 << 2) | (A1 << 1) | (A0 << 0)) << 1) | MCP23017_WR);