MSP432E401Y: I2C issue, MAP_I2CMasterControl sends address and a 0x00 byte

Hi,

  MAP_I2CMasterControl is what starts the I2C state machine. When you use I2C_MASTER_CMD_BURST_SEND_START, it means it begins with the first write data of a burst sequence. After the first data is sent, you are holding the bus idle until subsequent data are sent. The subsequent data are sent using the I2C_MASTER_CMD_BURST_SEND_CONT and the last data in the burst sequence is ended with the I2C_MASTER_CMD_BURST_SEND_FINISH. 

If you only have one data to write, then you should be using an example as follows using the I2C_MASTER_CMD_SINGLE_SEND flag.

MAP_I2CMasterControl(I2C7_BASE I2C_MASTER_CMD_SINGLE_SEND);

Below is an example code to read multiple data. You can mimic the code for the write operation. 

void
I2CReadCommand(uint32_t * pui32DataRx)
{
//
// Modify the data direction to true, so that seeing the address will
// indicate that the I2C Master is initiating a read from the slave.
//
MAP_I2CMasterSlaveAddrSet(I2C7_BASE, SHT21_I2C_ADDRESS, true);

//
// Setup for first read. Use I2C_MASTER_CMD_BURST_RECEIVE_START
// to start a burst mode read. The I2C master continues to own
// the bus at the end of this transaction.
//
MAP_I2CMasterControl(I2C7_BASE, I2C_MASTER_CMD_BURST_RECEIVE_START);

//
// Wait until master module is done transferring.
// The I2C module has a delay in setting the Busy flag in the register so
// there needs to be a delay before checking the Busy bit. The below loops
// wait until the Busy flag is set, and then wait until it is cleared to
// indicate that the transaction is complete. This can take up to 633 CPU
// cycles @ 100 kbit I2C Baud Rate and 120 MHz System Clock. Therefore, a
// while loop is used instead of SysCtlDelay.
//
while(!MAP_I2CMasterBusy(I2C7_BASE))
{
}
while(MAP_I2CMasterBusy(I2C7_BASE))
{
}

//
// Read the first byte data from the slave.
//
pui32DataRx[0] = MAP_I2CMasterDataGet(I2C7_BASE);

//
// Setup for the second read. Use I2C_MASTER_CMD_BURST_RECEIVE_CONT
// to continue the burst mode read. The I2C master continues to own
// the bus at the end of this transaction.
//
MAP_I2CMasterControl(I2C7_BASE, I2C_MASTER_CMD_BURST_RECEIVE_CONT);

//
// Wait until master module is done transferring.
//
while(!MAP_I2CMasterBusy(I2C7_BASE))
{
}
while(MAP_I2CMasterBusy(I2C7_BASE))
{
}

//
// Read the second byte data from the slave.
//
pui32DataRx[1] = MAP_I2CMasterDataGet(I2C7_BASE);

//
// Setup for the third read. Use I2C_MASTER_CMD_BURST_RECEIVE_FINISH
// to terminate the I2C transaction. At the end of this transaction,
// the STOP bit will be issued and the I2C bus is returned to the
// Idle state.
//
MAP_I2CMasterControl(I2C7_BASE, I2C_MASTER_CMD_BURST_RECEIVE_FINISH);

//
// Wait until master module is done transferring.
//
while(!MAP_I2CMasterBusy(I2C7_BASE))
{
}
while(MAP_I2CMasterBusy(I2C7_BASE))
{
}

//
// Note the third 8-bit data is the checksum byte. It will be
// left to the users as an exercise if they want to verify if the
// checksum is correct.
pui32DataRx[2] = MAP_I2CMasterDataGet(I2C7_BASE);

I rewrote the code calling the non FIFO functions.  The sample code does call I2C_MASTER_CMD_BURST_SEND_START and then uses the FIFO calls, however.  After rewriting it from scratch rather than using the examples, I have the code working entirely.  Thanks for your help