diff --git a/testline.ino b/testline.ino
index 3984b6d..237de60 100644
--- a/testline.ino
+++ b/testline.ino
@@ -10,17 +10,191 @@ LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
 uint8_t up_arrow[8]   = {0x04,0x0E,0x1F,0x1F,0x00,0x00,0x00,0x00};
 uint8_t down_arrow[8] = {0x00,0x00,0x00,0x1F,0x1F,0x0E,0x04,0x04};
 
+typedef enum InfoRet {
+  IR_UNKNOWN = -1,
+  IR_NORMAL = 0,
+  IR_UNSUCCESS
+} InfoRet;
+
 typedef struct InfoState {
   char* info;
-  int len;
-  int fullLines;
-  int Nlines;
-  int lastlinelen;
-  char *pos1, *pos2, *pos3;
+  list_node_t *pos1, *pos2, *pos3;
   list_t *wrap;
-  list_iterator_t *it;
 } InfoState;
 
+void lcd_blank_line() {
+  for (int i = 0; i < 15; ++i) {
+    lcd.print(' ');
+    //putchar(' ');
+  }
+}
+
+int lcd_print_between(char* str, int pos1, int pos2) {
+  //int i = 0;
+  int va = 0;
+  
+  char* p = str+pos1;
+  //int slen = strlen(str);
+  while (p < str+pos2) {
+    if (*p != '\n' && *p != '\r') {
+      lcd.print(*p);
+      //putchar(*p);
+      ++va;
+    } //else 
+    //if (i == 0){ ++i; } else 
+    //{
+    //  break;
+    //}
+    ++p;
+  }
+  
+  if (va < 15) {
+    for (int j = 15 - va; j > 0; --j) {
+      lcd.print(' ');
+      //putchar(' ');
+    }
+  }
+  //putchar('!');
+  return va;
+}
+
+list_t* aux_gen_wrap_list(list_t* wrap, char* text) {
+  if (wrap == NULL) {
+    wrap = list_new();
+  }
+  char* curr = text;
+  int suf = 0;
+  list_node_t *node;
+  if (list_rpush(wrap, list_node_new(-1)) == NULL) {
+    return NULL;
+  }
+  while (*curr != '\0') {
+    //printf("suf: %d\tpos: %d\n", suf, (unsigned int)(curr-text));
+    if (suf < 15) {
+      if (*curr != '\n' && *curr != '\r') {
+        ++suf;
+      } else {
+        if (list_rpush(wrap, list_node_new((unsigned int)(curr-text))) == NULL) {
+          return NULL;
+        }
+        suf = 0;
+      }
+    } else {
+      if (list_rpush(wrap, list_node_new((unsigned int)(curr-text))) == NULL) {
+        return NULL;
+      }
+      suf = (*curr != '\n' && *curr != '\r') ? 1 : 0;      
+    }
+    ++curr;
+  }
+  if (list_rpush(wrap, list_node_new((int)(curr-text))) == NULL) {
+    return NULL;
+  }
+  return wrap;
+}
+
+void initInfoState(InfoState* st, char* text) {
+  st->info = text;
+  st->wrap = list_new();
+  st->wrap = aux_gen_wrap_list(st->wrap, st->info);
+  st->pos1 = list_at(st->wrap, 0);
+  st->pos2 = st->pos3 = NULL;
+}
+
+InfoRet initInfoScreen(InfoState* st, char* text) {
+  initInfoState(st, text);
+  //printf("%d\n", st->wrap->len);
+  if (st->pos1 == NULL) {
+    return IR_UNKNOWN;
+  }
+  lcd.setCursor(0, 0);
+  if ((st->pos2 = st->pos1->next)) {
+    //printf("hello\n");
+    //printf("%d\n", st->pos2->val);
+    int tmp = lcd_print_between(st->info, 0, (int)st->pos2->val);
+    //printf("%d\n", tmp);
+    //printf("%d\n", st->wrap->len);
+    if ((st->pos3 = st->pos2->next)) {
+      //printf("\n");
+      lcd.setCursor(0, 1);
+      //printf("%d\n", st->pos2->val);
+      //printf("%d\n", st->pos3->val);
+      int tmp = lcd_print_between(st->info, (int)st->pos2->val, (int)st->pos3->val);
+      //printf("%d\n", tmp);
+      //printf("%d\n", st->wrap->len);
+    } else {
+      //printf("\n");
+      lcd.setCursor(0, 1);
+      lcd_blank_line();
+    }
+  } else {
+    return IR_UNKNOWN;
+  }
+  return IR_NORMAL;
+}
+
+InfoRet scrollDown(InfoState* st) {
+  if (st->pos2) {
+    st->pos1 = st->pos2;
+  } else {
+    return IR_UNKNOWN;
+  }
+  if (st->pos3) {
+    st->pos2 = st->pos3;
+  } else {
+    return IR_UNSUCCESS;
+  }
+  lcd.setCursor(0, 0);
+  int tmp = lcd_print_between(st->info, (int)st->pos1->val, (int)st->pos2->val);
+  if ((st->pos3 = st->pos3->next)) {
+    //printf("\n");
+    lcd.setCursor(0, 1);
+    int tmp = lcd_print_between(st->info, (int)st->pos2->val, (int)st->pos3->val);
+  } else {
+    //printf("\n");
+    lcd.setCursor(0, 1);
+    lcd_blank_line();
+  }
+  return IR_NORMAL;
+}
+
+InfoRet scrollUp(InfoState* st) {
+  if (st->pos2) {
+    st->pos3 = st->pos2;
+  } else {
+    return IR_UNKNOWN;
+  }
+  
+  if (st->pos1 == NULL) {
+    return IR_UNKNOWN;
+  } else if ((int)st->pos1->val == -1) {
+    return IR_UNSUCCESS;
+  } else {
+    st->pos2 = st->pos1;
+  }
+  
+  if ((st->pos1 = st->pos1->prev)) {
+    lcd.setCursor(0, 0);
+    if (st->pos1->val == -1) {
+      int tmp = lcd_print_between(st->info, 0, (int)st->pos2->val);
+    } else {
+      int tmp = lcd_print_between(st->info, (int)st->pos1->val, (int)st->pos2->val);
+    }
+  } else {
+    return IR_UNKNOWN;
+  }
+  //printf("\n");
+  lcd.setCursor(0, 1);
+  int tmp = lcd_print_between(st->info, (int)st->pos2->val, (int)st->pos3->val);
+  return IR_NORMAL;
+}
+
+void destoryInfoState(InfoState* st) {
+  st->pos1 = st->pos2 = st->pos3 = NULL;
+  list_destroy(st->wrap);
+  st->info = NULL;
+}
+
 void setup() {
   Serial.begin(9600);
   lcd.begin(16, 2);
@@ -37,9 +211,17 @@ void loop() {
   //String info = "hello,`world!wwwwwwwwwwwwwwww";
   InfoState st;
   initInfoScreen(&st, cinfo);
-  
+  for (int i = 0; i < 10; ++i) {
+    delay(1000);
+    scrollDown(&st);
+  }
+  for (int i = 0; i < 10; ++i) {
+    delay(1000);
+    scrollUp(&st);
+  }
+/*
 #ifdef DEBUG
-  Serial.println(String("len: ") + st.len);
+  //Serial.println(String("len: ") + st.len);
 #endif
 
 #ifdef DEBUG
@@ -73,198 +255,14 @@ void loop() {
     delay(1000);
     scrollUp(&st);
   }
-
+*/
   delay(3000);
 }
 
-list_t* aux_gen_wrap_list(list_t* wrap, char* text) {
-  if (wrap == NULL) {
-    wrap = list_new();
-  }
-  char* curr = text;
-  int suf = 0;
-  list_node_t *node;
-  if (list_rpush(wrap, list_node_new(0)) == NULL) {
-    return NULL;
-  }
-  while (*curr != '\0') {
-    //printf("suf: %d\tpos: %d\n", suf, (unsigned int)(curr-text));
-    if (suf < 15) {
-      if (*curr != '\n' && *curr != '\r') {
-        ++suf;
-      } else {
-        if (list_rpush(wrap, list_node_new((unsigned int)(curr-text))) == NULL) {
-          return NULL;
-        }
-        suf = 0;
-      }
-    } else {
-      if (list_rpush(wrap, list_node_new((unsigned int)(curr-text))) == NULL) {
-        return NULL;
-      }
-      suf = (*curr != '\n' && *curr != '\r') ? 1 : 0;      
-    }
-    ++curr;
-  }
-  if (list_rpush(wrap, list_node_new(strlen(text))) == NULL) {
-    return NULL;
-  }
-  return wrap;
-}
-
-void initInfoState(InfoState* st, char* text) {
-  st->info = text;
-  st->len = strlen(text);
-  st->fullLines = st->len / 15;
-  st->Nlines = (st->len + 14) / 15;
-  st->lastlinelen = st->len % 15;
-  st->pos1 = text;
-  st->pos2 = text;
-  st->pos3 = text;
-  st->wrap = list_new();
-  st->wrap = aux_gen_wrap_list(st->wrap, st->info);
-  st->it = list_iterator_new(st->wrap, LIST_HEAD);
-}
-
-void initInfoScreen(InfoState* st, char* text) {
-  initInfoState(st, text);
-  lcd.setCursor(0, 0);
-  
-  /*
-  if (*(st->pos1) == '\n' || *(st->pos1) == '\r') {
-    lcd_blank_line();
-    ++st->pos1;
-    ++st->pos2;
-  } else {
-    st->pos2 += lcd_print_line(st->pos1);
-  }
-  lcd.setCursor(0, 1);
-  if ((*(st->pos2) == '\n' || *(st->pos2) == '\r') && *(st->pos2 - 1) == *(st->pos2)) {
-    lcd_blank_line();
-  } else {
-    lcd_print_line(st->pos2);
-  }
-#ifdef DEBUG
-  //Serial.println(String("pos1: ") + st->pos1);
-  //Serial.println(String("pos2: ") + st->pos2);
-  Serial.println("init");
-  Serial.print(st->pos1-st->info);
-  Serial.println(String(" ")+(st->pos2-st->info));
-#endif
-  */
-}
-
-
-void scrollDown(InfoState* st) {
-  st->pos1 = st->pos2;
-  lcd.setCursor(0, 0);
-  if ((*(st->pos1) == '\n' || *(st->pos1) == '\r') && *(st->pos1 - 1) == *(st->pos1)) {
-    lcd_blank_line();
-    ++st->pos1;
-    ++st->pos2;
-  } else {
-    st->pos2 += lcd_print_line(st->pos1);
-  }
-  lcd.setCursor(0, 1);
-  if ((*(st->pos2) == '\n' || *(st->pos2) == '\r') && *(st->pos2 - 1) == *(st->pos2)) {
-    lcd_blank_line();
-  } else {
-    lcd_print_line(st->pos2);
-  }
-#ifdef DEBUG
-  //Serial.println(String("pos1: ") + st->pos1);
-  //Serial.println(String("pos2: ") + st->pos2);
-  Serial.print(st->pos1-st->info);
-  Serial.println(String(" ")+(st->pos2-st->info));
-#endif
-}
-
-void scrollUp(InfoState* st) {
-  if (st->pos1 > st->info) {
-    st->pos2 = st->pos1;
-    int i = 1;
-    int va = 1;
-    /*
-    int bound = min(st->pos1, 15);
-    Serial.println(String("bound: ")+bound);
-    while (i < bound) {
-      if (st->info[st->pos1-i] != '\n' && st->info[st->pos1-i] != '\r') {
-        ++i;
-      } else 
-      if (i == 1){ ++i; ++bound; } else 
-      {
-        break;
-      }
-    }
-    */
-    
-    /*
-    while (i < st->pos1-st->info && va < 15) {
-      if (st->info[st->pos1-i] != '\n' && st->info[st->pos1-i] != '\r') {
-        ++i;
-        ++va;
-      } else 
-      if (i == 1){ ++i; } else 
-      {
-        break;
-      }
-    }
-    
-    st->pos1 -= i;
-    */
-    bool is_blank = false;
-    while (st->pos1 > st->info && va <= 15) {
-      if (*(st->pos1) != '\n' && *(st->pos1) != '\r') {
-        ++i;
-        ++va;
-      } else if (*(st->pos1 - 1) == *(st->pos1)) {
-        is_blank = true;
-        --st->pos1;
-        break;
-      }
-      --st->pos1;
-    }
-    while (st->pos1 > st->info && (*(st->pos1) == '\n' || *(st->pos1) == '\r')) {
-      --st->pos1;
-    }
-    //st->pos1 -= i;
-    
-    lcd.setCursor(0, 0);
-    if (is_blank) {
-      lcd_blank_line();
-    } else {
-      lcd_print_line(st->pos1);
-    }
-    lcd.setCursor(0, 1);
-    if ((*(st->pos2) == '\n' || *(st->pos2) == '\r') && *(st->pos2 - 1) == *(st->pos2)) {
-      lcd_blank_line();
-    } else {
-      lcd_print_line(st->pos2);
-    }
-  }
-#ifdef DEBUG
-  //Serial.println(String("pos1: ") + st->pos1);
-  //Serial.println(String("pos2: ") + st->pos2);
-  Serial.print(st->pos1-st->info);
-  Serial.println(String(" ")+(st->pos2-st->info));
-#endif
-}
-
+/*
 int lcd_print_line(char* str) {
   int i = 0;
   int va = 0;
-  /*
-  int bound = min(strlen(str), 15);
-  while (i < bound) {
-    if (str[i] != '\n' && str[i] != '\r') {
-      lcd.print(str[i++]);
-    } else 
-    if (i == 0){ ++i; ++bound;} else 
-    {
-      break;
-    }
-  }
-  */
   int slen = strlen(str);
   while (i < slen && va < 15) {
     if (str[i] != '\n' && str[i] != '\r') {
@@ -287,55 +285,5 @@ int lcd_print_line(char* str) {
   }
   return i;
 }
-
-/*
-  Separate a substring that can be printed on one line, and return the 
-  original string position corresponding to the end of the substring.
- */
-/*
-char* aux_sub_line(char* str, char substr[16]) {
-  int suf = 0;
-  char* curr = str;
-  memset(substr, 0, 16);
-  
-  while (*curr != '\0' && suf < 15) {
-    if (*curr != '\n' && *curr != '\r') {
-      substr[suf++] = *(curr++);
-    } else 
-    if (curr == str){ ++curr; } else 
-    {
-      break;
-    }
-  }
-  
-#if !REFRESH
-  while (suf < 15) {
-    substr[suf++] = ' ';
-  }
-#endif
-  return curr;
-}
-
-char* aux_sub_line_rev(char* str, char substr[16]) {
-  int suf = 0;
-  char* curr = str;
-  memset(substr, 0, 16);
-  
-  while (*curr != '\0' && suf < 15) {
-    if (*curr != '\n' && *curr != '\r') {
-      substr[suf++] = *(curr--);
-    } else 
-    if (curr == str){ --curr; } else 
-    {
-      break;
-    }
-  }
-  
-  
-}
 */
-void lcd_blank_line() {
-  for (int i = 0; i < 15; ++i) {
-    lcd.print(' ');
-  }
-}
+