2 * 2 working correctly.

Test/Test.ino

@@ -1,11 +1,85 @@
-void setup() {
-    pinMode(2, OUTPUT);
+#include "TimerOne.h"
 
+const byte cath_low = 3, cath_high = 2;
+const byte anode_start = 4;
+
+void setup() {
+  pinMode(cath_low, OUTPUT);
+  pinMode(cath_high, OUTPUT);
+  for (int i = 0; i < 4; i++) {
+    pinMode(anode_start + i, OUTPUT);
   }
 
+  Serial.begin(115200);
+
+  Timer1.initialize();
+  Timer1.setPeriod(1000);
+  Timer1.attachInterrupt(displayOneLayer);
+}
+
+byte LED_status = 0;
+byte currentDisplayLayer = 0;
+
 void loop() {
-     digitalWrite(2, HIGH);
-     delay(2);
-     digitalWrite(2, LOW);
-     delay(14);
+  // if (Serial.available()) {
+  //   char input = Serial.read();
+  //   if (input >= '0' && input < '9') {
+  //     int LED_num = input - '0';
+  //     LED_status ^= 1 << LED_num;
+  //   }
+  // }
+  //   for (int i = 0; i < 8; i++) {
+  //     LED_status ^= 1 << i;
+  //     delay(75);
+  //   }
+
+  int count = 0;
+  while (true) {
+    randomSeed(analogRead(0));
+    int num = random(0, 8);
+    if (!(LED_status & (1 << num))) {
+      count++;
+      LED_status ^= 1 << num;
+      delay(100);
+    }
+    if (count >= 8) {
+      break;
+    }
+  }
+
+  delay(500);
+
+  while (true) {
+    randomSeed(analogRead(0));
+    int num = random(0, 8);
+    if (LED_status & (1 << num)) {
+      count--;
+      LED_status ^= 1 << num;
+      delay(100);
+    }
+
+    if (count <= 0) {
+      break;
+    }
+  }
+
+  delay(500);
+}
+
+void displayOneLayer() {
+  //   Serial.println(LED_status, BIN);
+  currentDisplayLayer = (currentDisplayLayer + 1) % 2;
+  if (currentDisplayLayer == 0) {
+    digitalWrite(cath_high, LOW);
+    for (int i = 0; i < 4; i++) {
+      digitalWrite(anode_start + i, (LED_status >> i) & 1);
+    }
+    digitalWrite(cath_low, HIGH);
+  } else {
+    digitalWrite(cath_low, LOW);
+    for (int i = 0; i < 4; i++) {
+      digitalWrite(anode_start + i, (LED_status >> (i + 4)) & 1);
+    }
+    digitalWrite(cath_high, HIGH);
+  }
 }