chore(ino): translate main.ino comments and Serial output to English

All Chinese comments, Serial.println strings, and inline notes
translated to English per the project's English-first codebase rule.
No logic changes.

Closes #11

main.ino

@@ -1,45 +1,45 @@
 /*
- * ESP32 原生硬件 PWM 控制程序 (适配 Core 3.x 版本)
- * 解决 'ledcSetup' was not declared 报错问题
+ * ESP32 native hardware PWM servo controller (ESP32 Arduino Core 3.x)
+ * Uses the updated ledcAttach/ledcWrite API (replaces deprecated ledcSetup).
  */
 
-// --- 1. 引脚定义 ---
-const int PIN_X = 14; 
-const int PIN_Y = 4;  
-const int PIN_Z = 5;  
-const int PIN_B = 18; 
-const int PIN_G = 23; 
+// --- 1. Pin assignments ---
+const int PIN_X = 14;  // X-axis servo
+const int PIN_Y = 4;   // Y-axis servo
+const int PIN_Z = 5;   // Z-axis servo
+const int PIN_B = 18;  // Base rotation servo
+const int PIN_G = 23;  // Gripper servo
 
-// --- 2. PWM 参数 (舵机标准) ---
-const int freq = 50;           // 频率 50Hz (周期 20ms)
-const int resolution = 12;     // 分辨率 12位 (数值范围 0-4095)
+// --- 2. PWM parameters (standard servo) ---
+const int freq = 50;        // 50 Hz (20 ms period)
+const int resolution = 12;  // 12-bit resolution (0–4095)
 
-// 舵机角度对应的占空比数值 (12位分辨率)
-// 0.5ms (0度)   -> 约 102
-// 1.5ms (90度)  -> 约 307
-// 2.5ms (180度) -> 约 512
+// Duty-cycle values for servo angles (12-bit, 50 Hz):
+//   0.5 ms (  0°) → ~102
+//   1.5 ms ( 90°) → ~307
+//   2.5 ms (180°) → ~512
 
 void setup() {
   Serial.begin(115200);
   delay(1000);
 
-  Serial.println("\n--- 使用 ESP32 Core 3.x LEDC 驱动初始化 ---");
+  Serial.println("\n--- ESP32 Core 3.x LEDC driver initializing ---");
 
-  // 在新版 Core 中，直接使用 ledcAttach(引脚, 频率, 分辨率)
+  // Core 3.x API: ledcAttach(pin, frequency, resolution)
   ledcAttach(PIN_X, freq, resolution);
   ledcAttach(PIN_Y, freq, resolution);
   ledcAttach(PIN_Z, freq, resolution);
   ledcAttach(PIN_B, freq, resolution);
   ledcAttach(PIN_G, freq, resolution);
 
-  // 初始归中
+  // Center all servos at startup
   writeAngle(PIN_X, 90); delay(500);
   writeAngle(PIN_Y, 90); delay(500);
   writeAngle(PIN_Z, 90); delay(500);
   writeAngle(PIN_B, 90); delay(500);
   writeAngle(PIN_G, 90); delay(500);
 
-  Serial.println("--- 5轴硬件 PWM 初始化完成 ---");
+  Serial.println("--- 5-axis hardware PWM ready ---");
 }
 
 void loop() {
@@ -47,7 +47,6 @@ void loop() {
     String cmd = Serial.readStringUntil('\n');
     cmd.trim();
 
-    // 根据指令解析并控制
     if      (cmd.startsWith("Servo_ArmX"))    writeAngle(PIN_X, extractAngle(cmd, "Servo_ArmX"));
     else if (cmd.startsWith("Servo_ArmY"))    writeAngle(PIN_Y, extractAngle(cmd, "Servo_ArmY"));
     else if (cmd.startsWith("Servo_ArmZ"))    writeAngle(PIN_Z, extractAngle(cmd, "Servo_ArmZ"));
@@ -56,33 +55,31 @@ void loop() {
       int a = extractAngle(cmd, "Servo_Gripper");
       if (a != -1) {
         writeAngle(PIN_G, a);
-        Serial.print("夹爪已转动至: "); Serial.println(a);
+        Serial.print("Gripper moved to: "); Serial.println(a);
       }
     }
   }
 }
 
 /**
- * 核心控制函数
- * pin: 控制的引脚号
- * angle: 目标角度 (0-180)
+ * Write a target angle to a servo pin.
+ * pin  : GPIO pin number
+ * angle: target angle in degrees (0–180, clamped)
  */
 void writeAngle(int pin, int angle) {
   if (angle < 0)   angle = 0;
   if (angle > 180) angle = 180;
 
-  // 线性映射计算占空比
-  // 0度 = 102, 180度 = 512
+  // Linear map: 0° → duty 102, 180° → duty 512
   int duty = (angle * (512 - 102) / 180) + 102;
 
-  // 在新版 Core 中，ledcWrite 直接接收引脚号和数值
+  // Core 3.x API: ledcWrite takes pin number directly
   ledcWrite(pin, duty);
 }
 
-// 提取命令中的数字
+/** Extract the numeric argument after a known command prefix. Returns -1 on failure. */
 int extractAngle(String cmd, String prefix) {
-  int prefixLen = prefix.length();
-  String valPart = cmd.substring(prefixLen);
+  String valPart = cmd.substring(prefix.length());
   if (valPart.length() > 0) return valPart.toInt();
   return -1;
 }