Retry function - I2C hung state handling PIC XC8

Question

This may be a very borderline Stack Overflow question, but I decided to post here because I'm dealing with the I2C protocol for a PIC MCU in XC8.

I'm learning how to talk with devices over I2C and it's going quite well, but I'm not sure of the best way to deal with a hung state from a not-acknowledge from a slave. The problem comes from the while() loops and the program not progressing until they're met (or not true - you know what I mean). My first method was with a watch dog reset, but I didn't like re-initializing everything any time something goes wrong.

I've consolidated all the writing of the registers to a function:

void I2Cwrite(unsigned char SLAVE, unsigned char REG, unsigned char DATA)
{
    SSPCON2bits.SEN = 1; // RESET
    while(SSPCON2bits.SEN == 1);
    SSPBUF = SLAVE;
    PIR1bits.SSPIF = 0;
    while(PIR1bits.SSPIF == 0);
    while(SSPCON2bits.ACKSTAT == 1);
    SSPBUF = REG;
    PIR1bits.SSPIF = 0;
    while(PIR1bits.SSPIF == 0);
    while(SSPCON2bits.ACKSTAT == 1);
    SSPBUF = DATA;
    PIR1bits.SSPIF = 0;
    while(PIR1bits.SSPIF == 0);
    while(SSPCON2bits.ACKSTAT == 1);
    PIR1bits.SSPIF = 0;
    SSPCON2bits.PEN = 1;
    while(PIR1bits.SSPIF == 0);
}

Then all I have to do is write my data to a function like this:

I2Cwrite(DRVwrite, 0x01, 0x07);
I2Cwrite(DRVwrite, 0x1A, 0b11011110);
I2Cwrite(DRVwrite, 0x16, 0b01010110);
I2Cwrite(DRVwrite, 0x17, 0b01011110);
I2Cwrite(DRVwrite, 0x1E, 0b00110000);
I2Cwrite(DRVwrite, 0x1B, 0b10011100);

If I fall into a hung state mid write, what is a good way to jump to the start of that particular I2C write function and try again?

Answer 1

The answer involves a Timer 2 to keep track of timing, and loops to give the ability of restarting from the beginning. The main send function is now grouped in a while(1) loop to allow multiple retries or parts. Each section of potential hung state is broken into a PART.

Timer 2 is set to a high priority interrupt, when overflows (because it has been waiting for too long) it sets a variable called TIMEOUT to 1. The ISR looks like:

void __interrupt(high_priority) High_ISR(void)
{
    if(PIR1bits.TMR2IF == 1)
    {
        TIMEOUT = 1;
        PIR1bits.TMR2IF = 0;
    }
}

When the program jumps back after servicing the ISR into waiting in the while loop, the while loops now have a function in them that breaks the wait if TIMEOUT equals 1.

void I2Cwrite(unsigned char SLAVE, unsigned char REG, unsigned char DATA)
{
    while(1)
    {
        TMR2 = 0;
        T2CONbits.TMR2ON = 1;
        
        if(PART == 0)
        {
            SSPCON2bits.SEN = 1; // RESET
            while(SSPCON2bits.SEN == 1);
            SSPBUF = SLAVE;
            PIR1bits.SSPIF = 0;
            while(PIR1bits.SSPIF == 0);
            while(SSPCON2bits.ACKSTAT == 1)
            {
                if(TIMEOUT == 1)
                {
                    break;
                }
            }
            T2CONbits.TMR2ON = 0;
        }
        if(PART == 1)
        {
            SSPBUF = REG;
            PIR1bits.SSPIF = 0;
            while(PIR1bits.SSPIF == 0);
            while(SSPCON2bits.ACKSTAT == 1)
            {
                if(TIMEOUT == 1)
                {
                    break;
                }
            }
            T2CONbits.TMR2ON = 0;
        }
        if(PART == 2)
        {
            SSPBUF = DATA;
            PIR1bits.SSPIF = 0;
            while(PIR1bits.SSPIF == 0);
            while(SSPCON2bits.ACKSTAT == 1)
            {
                if(TIMEOUT == 1)
                {
                    break;
                }
            }
            T2CONbits.TMR2ON = 0;
        }
        if(PART == 3)
        {
            PIR1bits.SSPIF = 0;
            SSPCON2bits.PEN = 1;
            while(PIR1bits.SSPIF == 0)
            {
                if(TIMEOUT == 1)
                {
                    break;
                }
            }
            T2CONbits.TMR2ON = 0;
        }
        if(TIMEOUT == 1) /////// Try again and start from beginning
        {
            PART = 0;
            TIMEOUT = 0;
        }
        else
        {
            if(PART == 3) // If the last part has been sent, break the while(1) loop
            {
                PART = 0;
                break;
            }
            else
            {
                PART++;
            }
        }
    }
}