关于TM4C123GH6PM的I2C，输出两个字节后就一直保持SDA高电平，SCL低电平的问题

int
main(void)
{
#if defined(TARGET_IS_TM4C129_RA0) ||                                         \
    defined(TARGET_IS_TM4C129_RA1) ||                                         \
    defined(TARGET_IS_TM4C129_RA2)
    uint32_t ui32SysClock;
#endif
    uint8_t pui32DataTx[NUM_I2C_DATA];
    uint8_t pui32DataRx[NUM_I2C_DATA];
    uint32_t ui32Index;
    uint32_t ui32Index1;

    //
    // Set the clocking to run directly from the external crystal/oscillator.
    // TODO: The SYSCTL_XTAL_ value must be changed to match the value of the
    // crystal on your board.
    //
#if defined(TARGET_IS_TM4C129_RA0) ||                                         \
    defined(TARGET_IS_TM4C129_RA1) ||                                         \
    defined(TARGET_IS_TM4C129_RA2)
    ui32SysClock = SysCtlClockFreqSet((SYSCTL_XTAL_25MHZ |
                                       SYSCTL_OSC_MAIN |
                                       SYSCTL_USE_OSC), 25000000);
#else
    SysCtlClockSet(SYSCTL_SYSDIV_1 | SYSCTL_USE_OSC | SYSCTL_OSC_MAIN |
                   SYSCTL_XTAL_16MHZ);
#endif

    //
    // The I2C0 peripheral must be enabled before use.
    //
    SysCtlPeripheralEnable(SYSCTL_PERIPH_I2C0);

    //
    // For this example I2C0 is used with PortB[3:2].  The actual port and
    // pins used may be different on your part, consult the data sheet for
    // more information.  GPIO port B needs to be enabled so these pins can
    // be used.
    // TODO: change this to whichever GPIO port you are using.
    //
    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOB);

    //
    // Configure the pin muxing for I2C0 functions on port B2 and B3.
    // This step is not necessary if your part does not support pin muxing.
    // TODO: change this to select the port/pin you are using.
    //
    GPIOPinConfigure(GPIO_PB2_I2C0SCL);
    GPIOPinConfigure(GPIO_PB3_I2C0SDA);

    //
    // Select the I2C function for these pins.  This function will also
    // configure the GPIO pins pins for I2C operation, setting them to
    // open-drain operation with weak pull-ups.  Consult the data sheet
    // to see which functions are allocated per pin.
    // TODO: change this to select the port/pin you are using.
    //
    GPIOPinTypeI2CSCL(GPIO_PORTB_BASE, GPIO_PIN_2);
    GPIOPinTypeI2C(GPIO_PORTB_BASE, GPIO_PIN_3);

    //
    // Enable loopback mode.  Loopback mode is a built in feature that is
    // useful for debugging I2C operations.  It internally connects the I2C
    // master and slave terminals, which effectively let's you send data as
    // a master and receive data as a slave.
    // NOTE: For external I2C operation you will need to use external pullups
    // that are stronger than the internal pullups.  Refer to the datasheet for
    // more information.
    //
    while(1)
    {

    //
    // Enable and initialize the I2C0 master module.  Use the system clock for
    // the I2C0 module.  The last parameter sets the I2C data transfer rate.
    // If false the data rate is set to 100kbps and if true the data rate will
    // be set to 400kbps.  For this example we will use a data rate of 100kbps.
    //
#if defined(TARGET_IS_TM4C129_RA0) ||                                         \
    defined(TARGET_IS_TM4C129_RA1) ||                                         \
    defined(TARGET_IS_TM4C129_RA2)
    I2CMasterInitExpClk(I2C0_BASE, ui32SysClock, false);
#else
    I2CMasterInitExpClk(I2C0_BASE, SysCtlClockGet(), false);
#endif

    //
    // Enable the I2C0 slave module. This module is enabled only for testing
    // purposes.  It does not need to be enabled for proper operation of the
    // I2Cx master module.
    //
    I2CSlaveEnable(I2C0_BASE);

    //
    // Set the slave address to SLAVE_ADDRESS.  In loopback mode, it's an
    // arbitrary 7-bit number (set in a macro above) that is sent to the
    // I2CMasterSlaveAddrSet function.
    //
    I2CSlaveInit(I2C0_BASE, SLAVE_ADDRESS);

    //
    // Tell the master module what address it will place on the bus when
    // communicating with the slave.  Set the address to SLAVE_ADDRESS
    // (as set in the slave module).  The receive parameter is set to false
    // which indicates the I2C Master is initiating a writes to the slave.  If
    // true, that would indicate that the I2C Master is initiating reads from
    // the slave.
    //
    I2CMasterSlaveAddrSet(I2C0_BASE, SLAVE_ADDRESS, false);

    //
    // Initalize the data to send.
    //

      pui32DataTx[0] = 0x02;
      pui32DataTx[1] = 0x20;

        //
        // Place the data to be sent in the data register
        //
        I2CMasterDataPut(I2C0_BASE, pui32DataTx[0]);

        //
        // Wait until master module is done transferring.
        //
        while(I2CMasterBusy(I2C0_BASE))
        {
        }

        I2CMasterControl(I2C0_BASE, I2C_MASTER_CMD_BURST_SEND_START);

        while(I2CMasterBusy(I2C0_BASE))
        {
        }

        ui32Index1 = I2CMasterErr(I2C0_BASE);

        while(I2CMasterErr(I2C0_BASE))
        {
        }

        I2CMasterDataPut(I2C0_BASE, pui32DataTx[1]);

        I2CMasterControl(I2C0_BASE, I2C_MASTER_CMD_BURST_SEND_FINISH);

        //
        // Wait until master module is done transferring.
        //
        while(I2CMasterBusy(I2C0_BASE))
        {
        }

        I2CSlaveDisable(I2C0_BASE);

    }
}