Incorrect data coming on PCF8574 via I2C

Dear all,

I am using TIVA C Launchpad for this study. I am using I2C from PB2 and PB3 pins and connected through PCF8574. Pull up resistor at I2C pins are of 4.7kOhm. On IC PCF8574 I have connected cathode of LEDs. So when I drive pin P0, P1, P2, P3 to zero the LEDs should glow.

Now the problem is in my program if I write from 0 to 9 the four LEDs should glow. Till 9 LED glow perfectly but as I write A it starts with 1 again.

Below is the waveform coming:

and below is the code:

#include <stdbool.h>
#include <stdint.h>
#include "inc/hw_i2c.h"
#include "inc/hw_gpio.h"
#include "inc/hw_memmap.h"
#include "inc/hw_types.h"
#include "driverlib/gpio.h"
#include "driverlib/i2c.h"
#include "driverlib/pin_map.h"
#include "driverlib/sysctl.h"
#include "driverlib/uart.h"
#include "utils/uartstdio.h"

//*****************************************************************************
//! - I2C0 peripheral
//! - GPIO Port B peripheral (for I2C0 pins)
//! - I2C0SCL - PB2
//! - I2C0SDA - PB3
//
// Number of I2C data packets to send.
//
//*****************************************************************************
#define NUM_I2C_DATA 3

//*****************************************************************************
#define SLAVE_ADDRESS 0x20

void I2C_data(unsigned char data)
{
	    I2CMasterDataPut(I2C0_BASE,data);
		I2CMasterControl(I2C0_BASE, I2C_MASTER_CMD_BURST_SEND_CONT);
		 while(I2CMasterBusy(I2C0_BASE)!=false)
		       {
		        	;
		       }
		 SysCtlDelay(15000000);
		 I2CMasterDataPut(I2C0_BASE,data);
		 I2CMasterControl(I2C0_BASE, I2C_MASTER_CMD_BURST_SEND_CONT);
		  while(I2CMasterBusy(I2C0_BASE)!=false)
		 	       {
		 	        	;
		 	       }
		 SysCtlDelay(15000000);
		 I2CMasterDataPut(I2C0_BASE,data);
		 I2CMasterControl(I2C0_BASE, I2C_MASTER_CMD_BURST_SEND_FINISH);
}

void I2C_String_Display(unsigned char *str)
{


 while(*str)
 {
	 I2C_data(*str);
	 str++;
 }
return;

}

int main(void)
{
    //
    // 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.
    //
    SysCtlClockSet(SYSCTL_SYSDIV_1 | SYSCTL_USE_OSC | SYSCTL_OSC_MAIN |
                   SYSCTL_XTAL_16MHZ);

    //
    // The I2C0 peripheral must be enabled before use.
    //
    SysCtlPeripheralReset(SYSCTL_PERIPH_I2C0);
    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.
    //
   HWREG(I2C0_BASE + I2C_O_MCR) = I2C_MCR_MFE ;

    //
    // 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.
    //
    I2CMasterInitExpClk(I2C0_BASE, SysCtlClockGet(), false);

    // 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);


        // Place the data to be sent in the data register
        //
       I2CMasterDataPut(I2C0_BASE,0x00);
       // I2CMasterDataPut(I2C0_BASE,data);
        //
        // Initiate send of data from the master.  Since the loopback
        // mode is enabled, the master and slave units are connected
        // allowing us to receive the same data that we sent out.
        //
       I2CMasterControl(I2C0_BASE, I2C_MASTER_CMD_BURST_SEND_START);
    
        // Wait until master module is done transferring.
        //
        while(I2CMasterBusy(I2C0_BASE)!=false)
       {
        	;
       }
       // SysCtlDelay(15000000);
        I2C_String_Display("A");

}

Please let me know if there is something wrong in the sting defined. Because if I write through single command or without pointer it is working correctly. But with string pointer it does not.