What`s the Problem with this Plot Program win32

/* - Comunicaçao Serial Entre o Microcontrolador e um Computador - */
/* ----------- Recebe Dados do Microcontrolador e Plota ---------- */

// To Do:
    // Verificar o Erro de quando clica duas vezes na tela
    // Verificar o Erro de porque de ve em quando ele recebe dados diferentes
    // Organizar Código
    //




#if defined(UNICODE) && !defined(_UNICODE)
    #define _UNICODE
#elif defined(_UNICODE) && !defined(UNICODE)
    #define UNICODE
#endif

#include <tchar.h>
#include <windows.h>
#include <stdio.h>
#include <stdlib.h>


#define BUTTON1 1
#define BUTTON2 2
#define IDM_FILE_NEW 3
#define IDM_FILE_OPEN 4
#define IDM_FILE_QUIT 5
#define STOP 6


/*  Declare Windows procedure  */
LRESULT CALLBACK WindowProcedure (HWND, UINT, WPARAM, LPARAM);
/*  Declare */
HWND textfield;
HWND TextBox;
FILE* fp;
HANDLE hCom;
HANDLE Handlethread;
DCB dcb;
BOOL fSuccess;
DWORD WINAPI THREAD1(LPVOID lpParam);
HWND hwnd;
DWORD ExitCode = 0;
int *lpArgPtr;
void AddMenus(HWND);
char textSaved[20];
char textSaved2[]={"Connecting."};
HDC hdc;

/*  Make the class name into a global variable  */
TCHAR szClassName[ ] = _T("EXAME DE SINCOPE VASOVAGAL");

int WINAPI WinMain (HINSTANCE hThisInstance,
                     HINSTANCE hPrevInstance,
                     LPSTR lpszArgument,
                     int nCmdShow)
{
                 /* This is the handle for our window */
    MSG messages;            /* Here messages to the application are saved */
    WNDCLASSEX wincl;        /* Data structure for the windowclass */

    /* The Window structure */
    wincl.hInstance = hThisInstance;
    wincl.lpszClassName = szClassName;
    wincl.lpfnWndProc = WindowProcedure;      /* This function is called by windows */
    wincl.style = CS_DBLCLKS;                 /* Catch double-clicks */
    wincl.cbSize = sizeof (WNDCLASSEX);

    /* Use default icon and mouse-pointer */
    wincl.hIcon = LoadIcon (NULL, IDI_APPLICATION);
    wincl.hIconSm = LoadIcon (NULL, IDI_APPLICATION);
    wincl.hCursor = LoadCursor (NULL, IDC_ARROW);
    wincl.lpszMenuName = "Menu";                 /* No menu */
    wincl.cbClsExtra = 0;                      /* No extra bytes after the window class */
    wincl.cbWndExtra = 0;                      /* structure or the window instance */
    /* Use Windows's default colour as the background of the window */
    wincl.hbrBackground = (HBRUSH) COLOR_BACKGROUND;

    /* Register the window class, and if it fails quit the program */
    if (!RegisterClassEx (&wincl))
        return 0;

    /* The class is registered, let's create the program*/
    hwnd = CreateWindowEx (
           0,                   /* Extended possibilites for variation */
           szClassName,         /* Classname */
           _T("EXAME DE SÍNCOPE VASOVAGAL"),       /* Title Text */
           WS_OVERLAPPEDWINDOW, /* default window */
           CW_USEDEFAULT,       /* Windows decides the position */
           CW_USEDEFAULT,       /* where the window ends up on the screen */
           544,                 /* The programs width */
           700,                 /* and height in pixels */
           HWND_DESKTOP,        /* The window is a child-window to desktop */
           NULL,                /* No menu */
           hThisInstance,       /* Program Instance handler */
           NULL                 /* No Window Creation data */
           );

    /* Make the window visible on the screen */
    ShowWindow (hwnd, nCmdShow);

    /* Run the message loop. It will run until GetMessage() returns 0 */
    while (GetMessage (&messages, NULL, 0, 0))
    {
        /* Translate virtual-key messages into character messages */
        TranslateMessage(&messages);
        /* Send message to WindowProcedure */
        DispatchMessage(&messages);
    }

    /* The program return-value is 0 - The value that PostQuitMessage() gave */
    return messages.wParam;
}


/*  This function is called by the Windows function DispatchMessage()  */

LRESULT CALLBACK WindowProcedure (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
//Caso o botao1 seja apertado;//
int     gwtstat = 0;
char *  t = &textSaved[0];
char pcCommPort[50] = "\\\\.\\COM4";
char SuceText[] = {"Connected"};
char stopedcon[]= {"Connection Stoped"};
char ErrorText[] = {"Error Connecting"};
char ConnectionError[] = {"Port Not Connected"};
int j;

/*--- Estrutura para quando pintar a tela ---*/
PAINTSTRUCT ps;
TEXTMETRIC  tm;     //Decide o tamanho das letras
TCHAR       teste[]={"Exame:"};

    switch (message)                  /* handle the messages */
    {
    case WM_CREATE:

        AddMenus(hwnd);//Adiciona Menus a janela

        TextBox = CreateWindow("EDIT",
                              "",
                              WS_BORDER | WS_CHILD | WS_VISIBLE,
                              10, 540,400,20,
                              hwnd,NULL,NULL,NULL);

        CreateWindow("BUTTON",
                     "SAVE",
                     WS_VISIBLE | WS_CHILD | WS_BORDER,
                     420, 540, 70, 20,
                     hwnd, (HMENU) 1, NULL, NULL);

        CreateWindow("BUTTON",
                     "START",
                     WS_VISIBLE | WS_CHILD | WS_BORDER,
                     420, 580, 70, 20,
                     hwnd, (HMENU) 2, NULL, NULL);

        CreateWindow("BUTTON",
                     "STOP",
                     WS_VISIBLE | WS_CHILD | WS_BORDER,
                     300, 580, 70, 20,
                     hwnd, (HMENU) 6, NULL, NULL);
                break;

    case WM_PAINT:
                hdc = BeginPaint(hwnd,&ps);
                FillRect(hdc,&ps.rcPaint,(HBRUSH)(COLOR_WINDOW+1)); //Pinta a Janela de Branco;
                SelectObject(hdc, GetStockObject( NULL_BRUSH ) );
                for (j=10;j<500;j++){
                    SetPixel(hdc,j,0,RGB(0,0,0));
                }
                 for (j=10;j<500;j++){
                    SetPixel(hdc,j,255,RGB(0,0,0));
                }
                  for (j=10;j<500;j++){
                    SetPixel(hdc,j,510,RGB(0,0,0));
                }
                //Rectangle(hdc,10,110,500,300);
                TextOut(hdc,1,515,teste,strlen(teste));    //How to change BackGround Colour? With SetBkColour
                EndPaint(hwnd,&ps);
                break;

    case WM_COMMAND:
        switch (LOWORD(wParam)){
            case BUTTON1:

                gwtstat = GetWindowText(TextBox,t, 20);
                ::MessageBox(hwnd,textSaved,textSaved,MB_OK);
                fopen("info.txt","a+");
                fwrite(teste,1,sizeof(teste),fp);
                //TerminateThread(Handlethread,ExitCode);

                break;

            case BUTTON2:
                hCom = CreateFile( pcCommPort,
                                GENERIC_READ | GENERIC_WRITE,
                                0,    // must be opened with exclusive-access
                                NULL, // no security attributes
                                OPEN_EXISTING, // must use OPEN_EXISTING
                                0,    // not overlapped I/O
                                NULL  // hTemplate must be NULL for comm devices
                    );


                if (hCom == INVALID_HANDLE_VALUE)
                {
                    ::MessageBox(hwnd,ConnectionError,ConnectionError,MB_OK);
                   return (1);
                }


               fSuccess = GetCommState(hCom, &dcb);

               if (!fSuccess)
               {    //failed
                    return (2);
               }

                dcb.BaudRate = CBR_9600;     // set the baud rate
                dcb.ByteSize = 8;             // data size, xmit, and rcv
                dcb.Parity = NOPARITY;        // no parity bit
                dcb.StopBits = TWOSTOPBITS;    // one stop bit

                fSuccess = SetCommState(hCom, &dcb);

                if (!fSuccess)
                {
                ::MessageBox(hwnd,ConnectionError,ConnectionError,MB_OK);
                  return (3);
                }else{

                    Handlethread = CreateThread(NULL,0,THREAD1,lpArgPtr,0,NULL);
                }
                ::MessageBox(hwnd,SuceText,SuceText,MB_OK);
                break;
            case IDM_FILE_NEW:
                Beep(100, 100);
                break;
            case IDM_FILE_OPEN:
                Beep(50, 100);
                break;
            case IDM_FILE_QUIT:
                SendMessage(hwnd,WM_CLOSE,0,0);
                break;
            case STOP:

                if (CloseHandle(hCom)==0){
                ::MessageBox(hwnd,ErrorText,NULL,MB_OK);
                }
                else{
                ::MessageBox(hwnd,stopedcon,stopedcon,MB_OK);
                }

                break;
        }

    case WM_DESTROY:
            //PostQuitMessage (0);       //send a WM_QUIT to the message queue

            break;

            default:                      /* for messages that we don't deal with */
                return DefWindowProc (hwnd, message, wParam, lParam);
            }

    return 0;
}


void AddMenus(HWND hwnd)
              {
              HMENU hMenubar;
              HMENU hMenu;
              hMenubar = CreateMenu();
              hMenu = CreateMenu();

              AppendMenuW(hMenu,MF_STRING, IDM_FILE_NEW, L"&New");
              AppendMenuW(hMenu,MF_STRING, IDM_FILE_OPEN, L"&Open");
              AppendMenuW(hMenu,MF_SEPARATOR, 0,NULL);
              AppendMenuW(hMenu,MF_STRING, IDM_FILE_QUIT, L"&Quit");
              AppendMenuW(hMenubar, MF_POPUP, (UINT_PTR) hMenu, L"&File");

              SetMenu(hwnd, hMenubar);
              }

    //SECOND THREAD;

DWORD WINAPI THREAD1(LPVOID lpParam){


    //PROBLEM STARTS HERE

        printf("I am inside the thread\n");

            int i = 0;
            int y = 0;
            bool tx;
            char PlotData[500] = {0};
            DWORD num;
            byte in[100]={0};

        while(1){

                tx = ReadFile(hCom,&in,2,&num,NULL);
                if (tx==0||num!=2){
                    printf("ERROR");
                    if (CloseHandle(hCom)==0){
                    ExitThread(ExitCode);
                }
                }else{
                printf("%x\t",(in[0]));
                }
                if(i>=500){

                    for(y=1;y<500;y++){
                        hdc = GetDC(hwnd);
                        SetPixel(hdc,y,PlotData[y],RGB(255,255,255));
                        ReleaseDC(hwnd,hdc);
                        PlotData[y-1] = PlotData[y];
                        PlotData[499] = (255 - in[0]);
                    }

                    for(y=0;y<500;y++){
                        hdc = GetDC(hwnd);
                        SetPixel(hdc,y,PlotData[y],RGB(255,0,0));
                        ReleaseDC(hwnd,hdc);
                    }


                }else if (i<500){
                        //hdc = GetDC(hwnd);
                        PlotData[i] = (255 - in[0]);
                        //ReleaseDC(hwnd,hdc);
                        i++;
                }
            }


        return NULL;
}