UART DMA PROBLEM ARM lpc1769

I want to send each other packages of about 5 bytes to uart use DMA. while each packet sent 1 I receive confirmation from the uart data using DMA.I change library lpc17xx.cmsis.driver.library \ uart_dma to do this.
but the problem I can only send a single packet for the first time and received data packets .I can not be sent next packet I try to create a loop but can not be reset DMA after each send.
What is my problem?
is there a way to solve it?

#include "lpc17xx_uart.h"
#include "lpc17xx_libcfg.h"
#include "lpc17xx_gpdma.h"
#include "lpc17xx_pinsel.h"


#define RX_BUF_SIZE     0x47

/************************** PRIVATE VARIABLES *************************/
uint8_t menu1[] =
"Hello NXP Semiconductors \n\r"
"UART interrupt mode demo using ring buffer \n\r\t "
"MCU LPC17xx - ARM Cortex-M3 \n\r\t "
"UART0 - 9600bps \n\r"
" This is a long string. It transferred in to DMA memory and transmit through Tx line \n\r"
" on UART0 peripheral. To use UART with DMA mode, FIFO function must be enabled \n\r";
uint8_t reset[]={0x56,0x00,0x26,0x00};
uint8_t menu3[] = "UART demo terminated!\n";
uint8_t takepicture[]={0x56,0x00,0x36,0x01,0x00};

// Receive buffer
__IO uint8_t rx_buf[RX_BUF_SIZE];

// Terminal Counter flag for Channel 0
__IO uint32_t Channel0_TC;

// Error Counter flag for Channel 0
__IO uint32_t Channel0_Err;

// Terminal Counter flag for Channel 1
__IO uint32_t Channel1_TC;

// Error Counter flag for Channel 1
__IO uint32_t Channel1_Err;



void DMA_IRQHandler (void);

void print_menu(void);

void DMA_IRQHandler (void)
{
        ........like library
}


int c_entry(void)
{

        uint8_t *rx_char;
        uint32_t idx,nn=0;
        // UART Configuration structure variable
        UART_CFG_Type UARTConfigStruct;
        // UART FIFO configuration Struct variable
        UART_FIFO_CFG_Type UARTFIFOConfigStruct;
        GPDMA_Channel_CFG_Type GPDMACfg;
        // Pin configuration for UART0
        PINSEL_CFG_Type PinCfg;


        PinCfg.Funcnum = 1;
        PinCfg.OpenDrain = 0;
        PinCfg.Pinmode = 0;
        PinCfg.Pinnum = 2;
        PinCfg.Portnum = 0;
        PINSEL_ConfigPin(&PinCfg);
        PinCfg.Pinnum = 3;
        PINSEL_ConfigPin(&PinCfg);

        UART_ConfigStructInit(&UARTConfigStruct);

        // Initialize UART0 peripheral with given to corresponding parameter
        UART_Init(LPC_UART0, &UARTConfigStruct);



        UART_FIFOConfigStructInit(&UARTFIFOConfigStruct);



        UARTFIFOConfigStruct.FIFO_DMAMode = ENABLE;


        UART_FIFOConfig(LPC_UART0, &UARTFIFOConfigStruct);


        UART_TxCmd(LPC_UART0, ENABLE);



 while(1){               // MY LOOP HERE
        GPDMA_Init();



         NVIC_DisableIRQ (DMA_IRQn);

           NVIC_SetPriority(DMA_IRQn, ((0x01<<3)|0x01));



        GPDMACfg.ChannelNum = 0;
        // Source memory
        if(nn==0)
        {
                    #define RX_BUF_SIZE 0x47
                  GPDMACfg.SrcMemAddr = (uint32_t) &reset;   //first package

                  GPDMACfg.DstMemAddr = 0;
                  GPDMACfg.TransferSize = sizeof(reset);
        }
        else
        {
                #define RX_BUF_SIZE 0x05
                GPDMACfg.SrcMemAddr = (uint32_t) &takepicture;  //The second package

                 GPDMACfg.TransferSize = sizeof(takepicture);
                nn=0;
        }
        // Transfer width - don't care
        GPDMACfg.TransferWidth = 0;
        // Transfer type
        GPDMACfg.TransferType = GPDMA_TRANSFERTYPE_M2P;
        // Source connection - don't care
        GPDMACfg.SrcConn = 0;
        // Destination connection
        GPDMACfg.DstConn = GPDMA_CONN_UART0_Tx;
        // Linker List Item - unused
        GPDMACfg.DMALLI = 0;
        // Setup channel with given parameter
        GPDMA_Setup(&GPDMACfg);

        // Setup GPDMA channel --------------------------------
        // channel 1
        GPDMACfg.ChannelNum = 1;
        // Source memory - don't care
        GPDMACfg.SrcMemAddr = 0;
        // Destination memory
        GPDMACfg.DstMemAddr = (uint32_t) &rx_buf;
        // Transfer size
        GPDMACfg.TransferSize = sizeof(rx_buf);
        // Transfer width - don't care
        GPDMACfg.TransferWidth = 0;
        // Transfer type
        GPDMACfg.TransferType = GPDMA_TRANSFERTYPE_P2M;
        // Source connection
        GPDMACfg.SrcConn = GPDMA_CONN_UART0_Rx;
        // Destination connection - don't care
        GPDMACfg.DstConn = 0;
        // Linker List Item - unused
        GPDMACfg.DMALLI = 0;
        GPDMA_Setup(&GPDMACfg);

        /* Reset terminal counter */
        Channel0_TC = 0;
        /* Reset Error counter */
        Channel0_Err = 0;

    // Enable interrupt for DMA
          NVIC_EnableIRQ (DMA_IRQn);

        // Enable GPDMA channel 0
        GPDMA_ChannelCmd(0, ENABLE);
        // Make sure GPDMA channel 1 is disabled
        GPDMA_ChannelCmd(1, DISABLE);

        /* Wait for GPDMA on UART0 Tx processing complete */
      while ((Channel0_TC == 0) && (Channel0_Err == 0));

    // Main loop - echos back to the terminal
   // while (1)
      {
        /* Reset terminal counter */
        Channel1_TC = 0;
        /* Reset Error counter */
        Channel1_Err = 0;

        // Setup channel with given parameter
        GPDMA_Setup(&GPDMACfg);

        // Enable GPDMA channel 1
        GPDMA_ChannelCmd(1, ENABLE);

        // Clear Rx buffer using DMA
        for (idx = 0; idx < RX_BUF_SIZE; idx++){
                rx_buf[idx] = 0;
        }

        // now, start receive character using GPDMA
        rx_char = (uint8_t *) &rx_buf;
      while ((Channel1_TC == 0) && (Channel1_Err == 0))
            {

                        // Check whether if there's any character received, then print it back
                        if (*rx_char != 0)
                        {
                                if(*rx_char ==0x0A){break;}
                                UART_Send(LPC_UART0, rx_char, 1, BLOCKING); //function   character is received on the hyper terminal
                                rx_char++;

                        }
               }
                                nn++;




         }


   }
    return 1;
}


int main(void)
{
    return c_entry();
}