I2C in MSP430F169 having USART module

shake4990 said:

      I2CIE |= TXRDYIE; //Enable Transmit interrupt

THis line enables interrupts for the TX event.

So the moment TXRDYIFG is set, the processor calls teh assigned ISR. I bet you don't have one, so the processor jumps into the void.
Sicn eyou want to handlew the TX event in your normal code flow (busy-waiting), you must not set any IE bit.

shake4990 said:

      I2CTCTL |= I2CTRX + I2CSTT + I2CSTP;      //Initiate Transfer

Setting I2CSTT adn I2CSTP at the same time, uses I2CNDAT register to determine the number of bytes to transmit. I don't see you setting it anywhere.
So you mus tnot set I2CSTP at this point. Rather set it when TXRDYIFG is set and you don't want to send more bytes. Then wait for it to clear again.

In I2CRead, you set I2CTRX, which actually causes transmit mode while you want to be in read mode. You must clear I2CTRX instead.
Here again, don't set I2CSTP. Set it when you got all the bytes you want. Do so before reading the last byte, so the USART won't start reading anothe rbyte before senting the stop.

In both functions, read and write, I2CRM needs to be set, because the number of bytes to transmit/receive is determined by software.

Also, the I2CSTP needs to be set before the last data byte is written to I2CDR, but not before the address has been acknowledged (unless you don't want to send anything but just to check for the slaves existence). Once TXRDYIFG is set, teh I2C expects you to write something to I2CDR, The flowchart doesn't show a way to end transmission here properly.
Similarly, when reading, you'll need to set I2CSTP before the last byte you want to read has arrived in I2CDR, else you will receive another byte.
According to the flowchart, the I2C doesn't wait until you actually read the byte before it acknowledges it and continues reading the next one.

I really don't like the USARTs I2C module. Much too high-level for easy use. :)

wow, thank you so much for all your time and effort! I really really appreciate it!

I actually did realize that after posting this code here, so I reformed it quite a bit and now my write function works perfectly, the problem is in the read function, where it is getting stuck at the receive interrupt place. And when I checked the register value of RXRDYIFG it was 0 only. So I dont know why is it showing that the code is stuck there. Can this be because of the character 'i' that I am using? Or it is the same reason of ISR that you mentioned above?

Also, while reading I will have to send the register address from where I want to read the data, so I will have to use the write function in read too!

Thank you once again! I don't know how to thank you more! :)

//I2C Initialisation

void I2C_Init(void)

{

      P3SEL |= 0x0A;    //Assign I2C pins to module

      P3DIR &= ~0x0A;

      U0CTL |= SYNC + I2C; // Synchronous, Switch USART0 to I2C mode, Set MSP430 as Master

      U0CTL &= ~I2CEN;

      I2CTCTL |= I2CTRX + I2CSSEL_2; // Set clock source as SMCLK, Transmit mode

      I2CSA = 0x48;     //Slave Address

      U0CTL |= I2CEN;   // Enable I2C

}

 //I2C Write Mode

void I2C_write(unsigned int address,unsigned char config)

{

    while (I2CDCTL & I2CBUSY); // waits for I2C to complete its working

    U0CTL |= MST;              // define Master Mode

    I2CTCTL |= I2CTRX;           // Transmit Mode

    I2CIFG &= ~TXRDYIFG;      // Clear Transmit Interrupt Flag

    I2CIE = TXRDYIE;          // enable Transmit ready interrupt

    I2CNDAT = 2;        // 2 bytes of data, counter

    I2CTCTL |= I2CSTT;  //Initiate Transfer

    I2CTCTL |= I2CSTP;   // I2C stop condition

    while((I2CIFG & TXRDYIFG)==0); //Wait for transmitter to be ready

    I2CDRB = address;                //Send register address

    while((I2CIFG & TXRDYIFG)==0); //Wait for transmitter to be ready

    I2CDRB = config;               // Send configuration data

    }

//I2C Read Mode

void I2C_read(unsigned int address, unsigned char i)

{

    while (I2CDCTL & I2CBUSY); // waits for I2C to complete its working

    U0CTL |= MST;              // define Master Mode

    I2CTCTL |= I2CTRX;         // Transmit Mode

    I2CIFG &= ~TXRDYIFG;      // Clear Transmit Interrupt Flag

    I2CIE = TXRDYIE;           // enable Transmit ready interrupt

    I2CNDAT = 1;

    I2CTCTL |= I2CSTT;              // Initiate transfer

    while((I2CIFG & TXRDYIFG)==0); 

    I2CDRB = address;   //Send data register address

    I2CTCTL &= ~I2CTRX;     // Receive Mode

    U0CTL |= MST;             // Master Mode

    I2CIFG &= ~RXRDYIFG;      // Clear Receive Interrupt Flag

    I2CIE &= ~TXRDYIE;        // Disable Transmit ready interrupt

    I2CIE = RXRDYIE;          // Enable Receive ready interrupt

    I2CNDAT = 1;

    I2CTCTL |= I2CSTT;        // Restart condition

    I2CTCTL |= I2CSTP;        // I2C stop condition

    while((I2CIFG & RXRDYIFG)==0);   //Wait for receiver to be ready

    i = I2CDRB;   // Receive Byte from AD7150

}

shake4990 said:

    I2CTCTL |= I2CSTT;        // Restart condition

    I2CTCTL |= I2CSTP;        // I2C stop condition

    while((I2CIFG & RXRDYIFG)==0);   //Wait for receiver to be ready

 

That's expected behavior with this code. :)

When you set I2CSTT, the USART sends start condition, slave address and direction, no matter whether it is a start or a restart. So when you set I2CSTP in the next line, the slave address hasn't been sent, the slave ahs not acked and no byte is in the process of receiving. So once the start is finished, no matter whether the slave has sent ACK or not, the stop will immediately follow and no byte is being requested and received ever.

You'll need to wait until I2CSTT is cleared, then set I2CSTP, then check for a NACK (no slave there) and when there was no NACK, then you may wait for a byte to come in.
(Maybe you'll need to check for a NACK before you set I2CSTP, I'm not sure of this detail)