MSP430F5340: MSP430F5340 hangs while checking UCTXSTT bit

Rekha K1

Prodigy 220 points

Part Number: MSP430F5340

i am facing an issue where MSP hangs while checking for UCTXSTT bit.

below is my code:

UCB1I2CSA = ucSlaveAddress;
UCB1CTL1 &= ~UCSWRST;

UCB1CTL1 |= UCTR | UCTXSTT; // I2C tx, start condition

while (((UCB1CTL1 & UCTXSTT) == 0) && (UCB1IFG & UCTXIFG));

if i remove ((UCB1CTL1 & UCTXSTT) and monitor only IFG flag it works and later i am checking for NACK. code works fine without any NACK after start condition is generated.

But why is it hanging when i am checking for UCTXSTT bit. ?

Thanks

Rekha

over 4 years ago

0 Ling Zhu2 over 4 years ago

TI__Genius 9570 points

Hi Rekha,

Please refer to example code.

Is it possible device hangs on a repeated START condition?

1212.C.zip

Thanks,

Ling

0 Rekha K1 over 4 years ago in reply to Ling Zhu2

Prodigy 220 points

Hi,

device will not hang on repeated start i mean when MSP is switched from Transmit mode to receiver mode.

initially start bit is sent and then i am polling for UCTXSTT bit to clear. but it never happens.

i even referred example code but it has interrupt based approach. but my code follows polling method.

attaching my file.

i2c battry.txt

 //I2C function//

uint8_t ucRxdata[2] = { };
    UCB1I2CSA = ucSlaveAddress;               // set Slave Address as 0x55
    UCB1CTL1 &= ~UCSWRST;

    UCB1CTL1 |= UCTR | UCTXSTT;             // I2C tx, start condition

    for (g_uloopcount = 0; g_uloopcount < LOOP_COUNT; g_uloopcount++)
    {
        if (((UCB1CTL1 & UCTXSTT) == 0) && (UCB1IFG & UCTXIFG))
       // if ((UCB1IFG & UCTXIFG))
        {
            break;
        }
    }
    if (g_uloopcount == LOOP_COUNT)
    {
        /* Stop the I2C transmission */
        UCB1CTL1 |= UCTXSTP;
        //send previous value
        return prev_value;
    }
    /* Check for NACK/ACK - after start+address byte */
    if (UCB1IFG & UCNACKIFG)
    {
        /* Stop the I2C transmission */
        UCB1CTL1 |= UCTXSTP;

        /* Clear the interrupt flag */
        UCB1IFG &= ~UCNACKIFG;

        //should reset MSP if Battery Percentage I2C is called first time and encounters I2C error
        if(one_time_flag == false)
        {
            one_time_flag = true;
            return BatteryFuelGuageI2CMasterReceive(ucSlaveAddress, ucCmd, ucDataLength, prev_value);
        }
        else
        {
            //send previous value
            return prev_value;
        }
    }
    UCB1TXBUF = ucCmd;
    // wait until cmd got sent
    for (g_uloopcount = 0; g_uloopcount < LOOP_COUNT; g_uloopcount++)
    {
        if (UCB1IFG & UCTXIFG)
        {
            break;
        }
    }
    if (g_uloopcount == LOOP_COUNT)
    {
        /* Stop the I2C transmission */
        UCB1CTL1 |= UCTXSTP;
        //send previous value
        return prev_value;
    }
    UCB1CTL1 &= ~UCTR;
    UCB1CTL1 |= UCTXSTT;
    //wait till the start condition is cleared
    for (g_uloopcount = 0; g_uloopcount < LOOP_COUNT; g_uloopcount++)
    {
        if ((UCB1CTL1 & UCTXSTT) == 0)
        {
            break;
        }
    }
    if (g_uloopcount == LOOP_COUNT)
    {
        /* Stop the I2C transmission */
        UCB1CTL1 |= UCTXSTP;
        //send previous value
        return prev_value;
    }

    /* Check for ACK */
    if (UCB1IFG & UCNACKIFG)
    {
        /* Stop the I2C transmission */
        UCB1CTL1 |= UCTXSTP;

        /* Clear the interrupt flag */
        UCB1IFG &= ~UCNACKIFG;
        //should reset MSP if Battery Percentage I2C is called first time and encounters I2C error
        if (one_time_flag == false)
        {
            one_time_flag = true;
            return BatteryFuelGuageI2CMasterReceive(ucSlaveAddress, ucCmd, ucDataLength, prev_value);
        }
        else
        {
            //send previous value
            return prev_value;
        }
    }

    unsigned int uiCounter = 0;
    unsigned int uiRxCounter = 2;
    while (uiRxCounter > 0)
    {
        for (g_uloopcount = 0; g_uloopcount < LOOP_COUNT; g_uloopcount++)
        {
            if (UCB1IFG & UCRXIFG)
            {
                break;
            }
        }
        if (g_uloopcount == LOOP_COUNT)
        {
            /* Stop the I2C transmission */
            UCB1CTL1 |= UCTXSTP;
            //send previous value
            return prev_value;
        }

        /* Check for ACK */
        if (UCB1IFG & UCNACKIFG)
        {
            /* Stop the I2C transmission */
            UCB1CTL1 |= UCTXSTP;

            /* Clear the interrupt flag */
            UCB1IFG &= ~UCNACKIFG;

            if (one_time_flag == false)
            {
                one_time_flag = true;
                return BatteryFuelGuageI2CMasterReceive(ucSlaveAddress, ucCmd, ucDataLength, prev_value);
            }
            else
            {
                //send previous value
                return prev_value;
            }

        }
        ucRxdata[uiCounter] = UCB1RXBUF; // Receive data from fuel gauge
        if (uiCounter == 0)
        {
            //Send stop condition.
            UCB1CTL1 |= UCTXSTP;
        }
        uiCounter++;
        uiRxCounter--;
    }

    UCB1IFG &= ~UCRXIFG;
    /* Clear USCI_B1 TX int flag */
    UCB1IFG &= ~UCTXIFG;

    g_uBatteryInfo = (uint16_t) ucRxdata[0] << 8 | ucRxdata[1]; //Transmit received data byte by byte

    return g_uBatteryInfo;

Thanks

Rekha

0 Bruce McKenney47378 over 4 years ago in reply to Rekha K1

Guru 88530 points

As shown in User Guide (SLAU208Q) Fig 38-12, STT won't clear until you recognize TXIFG and put something into TXBUF.

So I can see how the if() in the code you attached can fail, but not how the while() you posted could hang (since there the sense of the test is reversed).

In any case, go through that Figure and assure that your code follows the required steps.

0 Rekha K1 over 4 years ago in reply to Bruce McKenney47378

Prodigy 220 points

Bruce McKenney47378 said:
As shown in User Guide (SLAU208Q) Fig 38-12, STT won't clear until you recognize TXIFG and put something into TXBUF

does this means my code is not checking for flags properly?

also i did not understand which figure you are talking about!!!

0 Bruce McKenney47378 over 4 years ago in reply to Rekha K1

Guru 88530 points

Yes, the indicated if() should only be checking for TXIFG, since until you act upon that STT will always be 1.

The Figure is the diagram in the F5 User Guide (Rev Q) p. 1006. There should be a link to this document on the Product page. I keep this (or equivalent) page open all the time when I'm trying to write I2C code.

0 Rekha K1 over 4 years ago in reply to Bruce McKenney47378

Prodigy 220 points

thank you for your quick response.

ok i modified my code to monitor IFG flag -> look for NACK -> if ACK is received -> confirms that STT is cleared and i continue with code flow.

is my approach correct?

Thanks

Rekha

0 Bruce McKenney47378 over 4 years ago in reply to Rekha K1

Guru 88530 points

Sounds about right. (I don't have the diagram in front of me.)

You didn't mention it, but in response to the TXIFG you must actually write to TXBUF in order to proceed. (The bus is stalled until you do that.)

What does it do when you run it?

0 Rekha K1 over 4 years ago in reply to Bruce McKenney47378

Prodigy 220 points

Hi,

yes i am writing to TxBUF in response to IFG flag.

when we run it : slave's register address is written to TXBUF, once this command is executed we restart I2C by changing MSP to receiver mode to receive data from slave.

0 Bruce McKenney47378 over 4 years ago in reply to Rekha K1

Guru 88530 points

That sounds like what you set out to do. Good to hear.

0 Rekha K1 over 4 years ago in reply to Bruce McKenney47378

Prodigy 220 points

Thank you very much for your constant support. i will go ahead and close this ticket.

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MSP430F5340: MSP430F5340 hangs while checking UCTXSTT bit