C code to send AT comand and receive OK

[cdl121]

hardware detail:-
TMS320C5515
TELIT GL865
TXS0102(voltage level converer)

softwear detail:-
code composer studio v5
window 7(64bit)

want to send AT command and receive OK

code used for transmit at command

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Code C - [expand]
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void UartTxChar(unsigned char ch) //function to transmit character
{
    CSL_Status status;
    while (((hUart->uartRegs->LSR) & (0x0020)) != 0x0020);
    status = UART_write(hUart, &ch, 1, 0);
    if(status == CSL_SOK)
            {
              // printf("\n  sent %c",ch);
            }
            else
            {
                //printf("\n  Write Failed");
            }
    //USBSTK5515_waitusec(1000);
    //while(command != ch );
 
}
void UartTxString(unsigned char *str) //function to transmit string
{
 
//while(*str != '\0')
{
UartTxChar(*str);
*str++;
}
UartTxChar(0X0D);
UartTxChar(10);
USBSTK5515_waitusec(25000);//put it to wait for sending
USBSTK5515_waitusec(2500000);//put to wait for the ok

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code to receive ok

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Code C - [expand]
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void uart_rxIsr(void)
{
 
    //printf("rxc");
//UART_read(hUart,&command,1,0);
    command = CSL_FEXT(hUart->uartRegs->RBR,UART_RBR_DATA);
    //if (command == 's')
    //{
    //  gcount = 1;
 
//      dsp_call = 0;
    //}
 
    Recv[etc] = command;
    for( j = 0; j<=etc; j++ )
     printf("%c",Recv[j]);
    etc++;
}

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can anyone help me to find where is the problem and how to solve it