diff --git a/Project Backups/circuit1 [Autosaved].pdsprj b/Project Backups/circuit1 [Autosaved].pdsprj
deleted file mode 100644
index 3a58c6b..0000000
Binary files a/Project Backups/circuit1 [Autosaved].pdsprj and /dev/null differ
diff --git a/circuit1.pdsprj b/circuit1.pdsprj
deleted file mode 100644
index 59bb1eb..0000000
Binary files a/circuit1.pdsprj and /dev/null differ
diff --git a/homework5/.eide/eide.json b/homework5/.eide/eide.json
index 8e7c5be..a837da6 100644
--- a/homework5/.eide/eide.json
+++ b/homework5/.eide/eide.json
@@ -19,7 +19,8 @@
   "targets": {
     "Debug": {
       "excludeList": [
-        "src/test.c"
+        "src/test.c",
+        "src/test1.c"
       ],
       "toolchain": "Keil_C51",
       "compileConfig": {
diff --git a/homework5/src/homework5.h b/homework5/src/homework5.h
index 0051786..5e3dee5 100644
--- a/homework5/src/homework5.h
+++ b/homework5/src/homework5.h
@@ -3,7 +3,7 @@
  * this header defines:
  * variables:
  * 1. pin numbers to control the LED and the Seg.
- * 2. sdf for timer
+ * 2. seg chars to display the number on the Seg.
  * functions:
  * 1. control the LED and the Seg.
  * 2. to display the number on the Seg.
@@ -30,6 +30,25 @@ sbit ADDR1 = P1 ^ 1; // to B(A1)
 sbit ADDR2 = P1 ^ 2; // to C(A2)
 sbit ADDR3 = P1 ^ 3; // to E1
 sbit ENLED = P1 ^ 4; // to E2 & E3
+// seg chars:
+unsigned char code LedChar[] = {
+    0xC0,
+    0xF9,
+    0XA4,
+    0XB0,
+    0X99,
+    0X92,
+    0X82,
+    0XF8,
+    0X80,
+    0X90,
+    0X88,
+    0X83,
+    0XC6,
+    0XA1,
+    0X86,
+    0X8E,
+};
 
 // functions:
 // 38 transistors controller:
diff --git a/homework5/src/test1.c b/homework5/src/test1.c
index c5c0a07..2a2f797 100644
--- a/homework5/src/test1.c
+++ b/homework5/src/test1.c
@@ -3,25 +3,6 @@
 // display the last 6 digits of your student ID on the Seg.
 
 #include "homework5.h"
-
-unsigned char code LedChar[] = {
-    0xC0,
-    0xF9,
-    0XA4,
-    0XB0,
-    0X99,
-    0X92,
-    0X82,
-    0XF8,
-    0X80,
-    0X90,
-    0X88,
-    0X83,
-    0XC6,
-    0XA1,
-    0X86,
-    0X8E,
-};
 unsigned char LedBuff[6] = {
     0xFF, 0XFF, 0XFF, 0XFF, 0XFF, 0XFF};
 unsigned char i = 0;
diff --git a/homework5/src/test2.c b/homework5/src/test2.c
new file mode 100644
index 0000000..10c81bd
--- /dev/null
+++ b/homework5/src/test2.c
@@ -0,0 +1,84 @@
+// test2.c
+// 不使用中断，让数码管动态显示秒表
+// display the stopwatch on the Seg. without using interrupt.
+/*
+ * seg display format:
+ * 00.00.00
+ * HH.MM.SS
+ * HH: hour, MM: minute, SS: second
+ * dot . is dp
+ */
+
+/*
+ * how it work?
+ * 1. sleep 1s
+ * 2. count the seconds, minutes, hours.
+ * 3. reset the seconds, minutes when it reaches 60.
+ * 4. reset all when everything overflow.
+ * 5. log the number in the buffer.
+ * 6. display the number on the Seg.
+ */
+#include "homework5.h"
+unsigned char LedBuff[6] = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF}; // buffer to store the seg chars.
+
+void test2()
+{
+    unsigned char second       = 0; // to count the seconds.
+    unsigned char minute       = 0; // to count the minutes.
+    unsigned char hour         = 0; // to count the hours.
+    unsigned char i            = 0; // to count the times.
+    unsigned long time_counter = 0;
+
+    while (1) {
+        for (i = 0; i < 6; i++) {
+            // display number
+            set38Transistors(i);
+            P2 = LedBuff[i];
+            // display dot
+            if (i == 2 || i == 4) {
+                // 2nd dot between the minutes and seconds.
+                // 4th dot between the hours and minutes.
+                BUS8DP = 0; // display the dot.
+            } else {
+                BUS8DP = 1; // hide the dot on other places.
+            }
+
+            timer(1); // delay 1ms.
+            time_counter++;
+
+            // update time when 1000ms passed.
+            if (time_counter >= 1000) {
+                time_counter = 0; // reset the counter.
+                second++;         // count the seconds.
+                // solve unit overflow.
+                // second overflow
+                if (second >= 60) {
+                    second = 0; // reset the second.
+                    minute++;   // count the minutes.
+                }
+                // minute overflow.
+                if (minute >= 60) {
+                    minute = 0; // reset the minute.
+                    hour++;     // count the hours.
+                }
+                // everything overflow.
+                if (hour >= 99 && second >= 59 && minute >= 59) {
+                    hour   = 0; // reset the hour.
+                    second = 0; // reset the second.
+                    minute = 0; // reset the minute.
+                }
+            }
+            // log the number in the buffer.
+            LedBuff[5] = LedChar[hour / 10];   // log the hour tens.
+            LedBuff[4] = LedChar[hour % 10];   // log the hour units.
+            LedBuff[3] = LedChar[minute / 10]; // log the minute tens.
+            LedBuff[2] = LedChar[minute % 10]; // log the minute units.
+            LedBuff[1] = LedChar[second / 10]; // log the second tens.
+            LedBuff[0] = LedChar[second % 10]; // log the second units.
+        }
+    }
+}
+void main()
+{
+    test2();
+}
\ No newline at end of file