Timer_Callback - Problem

#define GRAPH_Y_ORIG    35
#define GRAPH_X_ORIG     5

#define AXIS_Y_LEN      165
#define AXIS_X_LEN      310


void Timer_Callback(void const *arg) {

int adcValue;
int x_new = 5;
int y_new;
int dif;
int j, k;

 if(x_cnt == 311) {
        GLCD_ClearScreen();
        Init_GLCD();
        x_cnt = 0;
        i = 0;
 }

ADC_StartConversion();
while(ADC_ConversionDone()<0);
adcValue = ADC_GetValue();

x_new = x_new + x_cnt;
x_cnt = x_cnt + 1;

y_new = ((165.0f / 1024.0f) * adcValue) - 165.0f;
y_new = fabs(y_new) + 35;

 if(i == 1) {

        GLCD_SetForegroundColor(GLCD_COLOR_YELLOW);
        GLCD_DrawPixel(x_new, y_new);

        if(y_old < y_new) {

                dif = y_new - y_old;

                for(j=0; j<=dif; j++) {
                        y_old = y_old + 1;
                        GLCD_SetForegroundColor(GLCD_COLOR_YELLOW);
                        GLCD_DrawPixel(x_old, y_old);
                }
        }

        else if(y_old > y_new) {

                dif = y_old - y_new;

                for(k=0; k<=dif; k++) {
                        y_old = y_old - 1;
                        GLCD_SetForegroundColor(GLCD_COLOR_YELLOW);
                        GLCD_DrawPixel(x_old, y_old);
                }
        }

        else {
                GLCD_SetForegroundColor(GLCD_COLOR_YELLOW);
                GLCD_DrawPixel(x_new, y_new);
        }

        x_old = x_new;
        y_old = y_new;
 }



else {
        GLCD_SetForegroundColor(GLCD_COLOR_YELLOW);
        GLCD_DrawPixel(x_new, y_new);

        x_old = x_new;
        y_old = y_new;
        i = 1;
 }
}

int main(void)
{
        ADC_Initialize();
        GLCD_Initialize();
        Init_GLCD();




        id = osTimerCreate(osTimer(Timer), osTimerPeriodic, NULL);




        if(id)
                osTimerStart(id, 1);
}