CCS/MSP430FR2476: I2C Communication not reading in real data

Michelle Bryson

Part Number: MSP430FR2476

Tool/software: Code Composer Studio

I am trying to program I2C communication between the MSP430 and a battery gauge (LTC2943). My read functions are only returning zeros. This is the read function:

void i2cReceive(uint8_t regAddress, uint8_t buffer, uint8_t bufferSize){
    uint8_t i;

    EUSCI_B_I2C_setSlaveAddress(EUSCI_B0_BASE, LTC2943_SLAVE_ADDRESS);
    EUSCI_B_I2C_setMode(EUSCI_B0_BASE, EUSCI_B_I2C_TRANSMIT_MODE);
    EUSCI_B_I2C_enable(EUSCI_B0_BASE);

    while (EUSCI_B_I2C_SENDING_STOP == EUSCI_B_I2C_masterIsStopSent(EUSCI_B0_BASE));
    EUSCI_B_I2C_masterSendStart(EUSCI_B0_BASE);

    // switch to receiver mode
    EUSCI_B_I2C_setMode(EUSCI_B0_BASE, EUSCI_B_I2C_RECEIVE_MODE);

    for(i=0; i<bufferSize; i++){
        buffer = EUSCI_B_I2C_masterReceiveMultiByteNext(EUSCI_B0_BASE);
        buffer++;
    }

    EUSCI_B_I2C_masterReceiveMultiByteStop(EUSCI_B0_BASE);
}

And this is one of the functions to read from a specific register:

uint8_t getControl(){
    uint8_t control = 0;
    i2cReceive(CONTROL_ADDRESS, control, sizeof(control));

    return control;
}

Sometimes it would get stuck in this while loop in i2cReceive():

while (EUSCI_B_I2C_SENDING_STOP == EUSCI_B_I2C_masterIsStopSent(EUSCI_B0_BASE));

When I commented that line out, it would run, but every register would return zero. I also tried using different functions like EUSCI_B_I2C_slaveGetData() but that just returned 255 each time.

over 5 years ago

0 Bruce McKenney over 5 years ago

Guru 100785 points

> EUSCI_B_I2C_masterSendStart(EUSCI_B0_BASE);

> EUSCI_B_I2C_setMode(EUSCI_B0_BASE, EUSCI_B_I2C_RECEIVE_MODE);

I think you need to send regAddress to the device somewhere in here, maybe something like

> EUSCI_B_I2C_masterSendSingleByte(EUSCI_B0_BASE, regAddress);

> EUSCI_B_I2C_setMode(EUSCI_B0_BASE, EUSCI_B_I2C_RECEIVE_MODE);

> EUSCI_B_I2C_masterSendStart(EUSCI_B0_BASE);

0 Michelle Bryson over 5 years ago in reply to Bruce McKenney

Prodigy 40 points

You're right, I had forgotten to send the register address. I updated my code to include this, but I'm getting the same result.

Here's my updated code:

void i2cReceive(uint8_t regAddress, uint8_t *buffer, uint8_t bufferSize){
    uint8_t i;

    EUSCI_B_I2C_setSlaveAddress(EUSCI_B0_BASE, LTC2943_SLAVE_ADDRESS);
    EUSCI_B_I2C_setMode(EUSCI_B0_BASE, EUSCI_B_I2C_TRANSMIT_MODE);
    EUSCI_B_I2C_enable(EUSCI_B0_BASE);


    EUSCI_B_I2C_masterSendStart(EUSCI_B0_BASE);
    EUSCI_B_I2C_slavePutData(EUSCI_B0_BASE, regAddress);

    // switch to receiver mode
    EUSCI_B_I2C_setMode(EUSCI_B0_BASE, EUSCI_B_I2C_RECEIVE_MODE);

    EUSCI_B_I2C_masterReceiveStart(EUSCI_B0_BASE);

    for(i=0; i<bufferSize; i++){
        *buffer = EUSCI_B_I2C_masterReceiveMultiByteNext(EUSCI_B0_BASE);
        buffer++;
    }

    EUSCI_B_I2C_masterReceiveMultiByteStop(EUSCI_B0_BASE);
    while (EUSCI_B_I2C_SENDING_STOP == EUSCI_B_I2C_masterIsStopSent(EUSCI_B0_BASE));
}

uint8_t getControl(){
    uint8_t control = 0;
    i2cReceive(CONTROL_ADDRESS, &control, sizeof(control));

    return control;
}

0 Bruce McKenney over 5 years ago in reply to Michelle Bryson

Guru 100785 points

> EUSCI_B_I2C_masterSendStart(EUSCI_B0_BASE);

> EUSCI_B_I2C_slavePutData(EUSCI_B0_BASE, regAddress);

slavePutData doesn't do what you want (it doesn't wait for TXIFG). Did masterSendSingleByte not work?

0 Michelle Bryson over 5 years ago in reply to Bruce McKenney

Prodigy 40 points

If I change it to masterSendSingleByte it gets stuck in this while loop within masterSendSingleByte

//Poll for transmit interrupt flag.
    while (!(HWREG16(baseAddress + OFS_UCBxIFG) & UCTXIFG)) ;

0 Bruce McKenney over 5 years ago in reply to Michelle Bryson

Guru 100785 points

Just to be clear: SendSingleByte does a Start, a transmit, and a Stop, so if you use it you shouldn't call SendStart separately.

What is the value of LTC2943_SLAVE_ADDRESS? On the one hand, I don't think you would have gotten this far if it were incorrect, but on the other hand that line of code is where I would expect it to fail if you were getting a NACK. Based on data sheet (2943FA) Fig 5, I would expect it to be 0x64.

0 Michelle Bryson over 5 years ago in reply to Bruce McKenney

Prodigy 40 points

I got 0x64 for the address as well. I just commented out the sendStart before the sendSingleByte and it's still getting stuck in the same while loop.

0 Bruce McKenney over 5 years ago in reply to Michelle Bryson

Guru 100785 points

Looking at the source, EUSCI_B_I2C_masterReceiveMultiByteNext doesn't wait for RXIFG to be set. (No this wasn't obvious to me either.) The variant that does wait for RXIFG is EUSCI_B_I2C_masterReceiveSingle.

I don't have your device, but I was able to read (repeatedly) the WHO_AM_I (0x0F) register from an LIS3DH using this version:

void i2cReceive(uint8_t regAddress, uint8_t *buffer, uint8_t bufferSize){
    uint8_t i;

    EUSCI_B_I2C_setSlaveAddress(EUSCI_B0_BASE, LTC2943_SLAVE_ADDRESS);
    EUSCI_B_I2C_setMode(EUSCI_B0_BASE, EUSCI_B_I2C_TRANSMIT_MODE);
    EUSCI_B_I2C_enable(EUSCI_B0_BASE);
#if BMC
    EUSCI_B_I2C_masterSendSingleByte(EUSCI_B0_BASE, regAddress);
    EUSCI_B_I2C_setMode(EUSCI_B0_BASE, EUSCI_B_I2C_RECEIVE_MODE);
    EUSCI_B_I2C_masterSendStart(EUSCI_B0_BASE);
#else
    EUSCI_B_I2C_masterSendStart(EUSCI_B0_BASE);
    EUSCI_B_I2C_slavePutData(EUSCI_B0_BASE, regAddress);
    // switch to receiver mode
    EUSCI_B_I2C_setMode(EUSCI_B0_BASE, EUSCI_B_I2C_RECEIVE_MODE);
    EUSCI_B_I2C_masterReceiveStart(EUSCI_B0_BASE);
#endif // BMC

    for(i=0; i<bufferSize; i++){
#if BMC
        *buffer = EUSCI_B_I2C_masterReceiveSingle(EUSCI_B0_BASE);
#else
        *buffer = EUSCI_B_I2C_masterReceiveMultiByteNext(EUSCI_B0_BASE);
#endif
        buffer++;
    }
    EUSCI_B_I2C_masterReceiveMultiByteStop(EUSCI_B0_BASE);
    while (EUSCI_B_I2C_SENDING_STOP == EUSCI_B_I2C_masterIsStopSent(EUSCI_B0_BASE));
}

[Edit: Fixed the duplicate code (it still works). Posting it took a few tries.]

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CCS/MSP430FR2476: I2C Communication not reading in real data