diff --git a/README.adoc b/README.adoc
index 816b2ee..a6317c3 100644
--- a/README.adoc
+++ b/README.adoc
@@ -5,6 +5,16 @@ This library allows an Arduino board with USB capabilities to act as a Keyboard.
 For more information about this library please visit us at
 https://www.arduino.cc/reference/en/language/functions/usb/keyboard/
 
+= Contributors =
+
+Original code (pre-library): Peter Barrett
+
+Contributor: MRNIU
+
+= Usage =
+
+See examples/Serial/Serial.ino
+
 == License ==
 
 Copyright (c) Arduino LLC. All right reserved.
diff --git a/src/Keyboard.cpp b/src/Keyboard.cpp
index 4a948f6..fbc895e 100644
--- a/src/Keyboard.cpp
+++ b/src/Keyboard.cpp
@@ -35,32 +35,32 @@ static const uint8_t _hidReportDescriptor[] PROGMEM = {
     0xa1, 0x01,                    // COLLECTION (Application)
     0x85, 0x02,                    //   REPORT_ID (2)
     0x05, 0x07,                    //   USAGE_PAGE (Keyboard)
-   
+
   0x19, 0xe0,                    //   USAGE_MINIMUM (Keyboard LeftControl)
     0x29, 0xe7,                    //   USAGE_MAXIMUM (Keyboard Right GUI)
     0x15, 0x00,                    //   LOGICAL_MINIMUM (0)
     0x25, 0x01,                    //   LOGICAL_MAXIMUM (1)
     0x75, 0x01,                    //   REPORT_SIZE (1)
-    
+
   0x95, 0x08,                    //   REPORT_COUNT (8)
     0x81, 0x02,                    //   INPUT (Data,Var,Abs)
     0x95, 0x01,                    //   REPORT_COUNT (1)
     0x75, 0x08,                    //   REPORT_SIZE (8)
     0x81, 0x03,                    //   INPUT (Cnst,Var,Abs)
-    
+
   0x95, 0x06,                    //   REPORT_COUNT (6)
     0x75, 0x08,                    //   REPORT_SIZE (8)
     0x15, 0x00,                    //   LOGICAL_MINIMUM (0)
     0x25, 0x73,                    //   LOGICAL_MAXIMUM (115)
     0x05, 0x07,                    //   USAGE_PAGE (Keyboard)
-    
+
   0x19, 0x00,                    //   USAGE_MINIMUM (Reserved (no event indicated))
     0x29, 0x73,                    //   USAGE_MAXIMUM (Keyboard Application)
     0x81, 0x00,                    //   INPUT (Data,Ary,Abs)
     0xc0,                          // END_COLLECTION
 };
 
-Keyboard_::Keyboard_(void) 
+Keyboard_::Keyboard_(void)
 {
 	static HIDSubDescriptor node(_hidReportDescriptor, sizeof(_hidReportDescriptor));
 	HID().AppendDescriptor(&node);
@@ -91,16 +91,16 @@ const uint8_t _asciimap[128] =
 	0x00,             // ETX
 	0x00,             // EOT
 	0x00,             // ENQ
-	0x00,             // ACK  
+	0x00,             // ACK
 	0x00,             // BEL
 	0x2a,			// BS	Backspace
 	0x2b,			// TAB	Tab
 	0x28,			// LF	Enter
-	0x00,             // VT 
-	0x00,             // FF 
-	0x00,             // CR 
-	0x00,             // SO 
-	0x00,             // SI 
+	0x00,             // VT
+	0x00,             // FF
+	0x00,             // CR
+	0x00,             // SO
+	0x00,             // SI
 	0x00,             // DEL
 	0x00,             // DC1
 	0x00,             // DC2
@@ -110,13 +110,13 @@ const uint8_t _asciimap[128] =
 	0x00,             // SYN
 	0x00,             // ETB
 	0x00,             // CAN
-	0x00,             // EM 
+	0x00,             // EM
 	0x00,             // SUB
 	0x00,             // ESC
-	0x00,             // FS 
-	0x00,             // GS 
-	0x00,             // RS 
-	0x00,             // US 
+	0x00,             // FS
+	0x00,             // GS
+	0x00,             // RS
+	0x00,             // US
 
 	0x2c,		   //  ' '
 	0x1e|SHIFT,	   // !
@@ -219,93 +219,90 @@ const uint8_t _asciimap[128] =
 
 uint8_t USBPutChar(uint8_t c);
 
-// press() adds the specified key (printing, non-printing, or modifier)
-// to the persistent key report and sends the report.  Because of the way 
-// USB HID works, the host acts like the key remains pressed until we 
-// call release(), releaseAll(), or otherwise clear the report and resend.
-size_t Keyboard_::press(uint8_t k) 
+size_t Keyboard_::set(uint8_t k, bool s)
 {
 	uint8_t i;
 	if (k >= 136) {			// it's a non-printing key (not a modifier)
 		k = k - 136;
 	} else if (k >= 128) {	// it's a modifier key
-		_keyReport.modifiers |= (1<<(k-128));
+		if(s) _keyReport.modifiers |= (1<<(k-128));
+		else _keyReport.modifiers |= (1<<(k-128));
 		k = 0;
 	} else {				// it's a printing key
 		k = pgm_read_byte(_asciimap + k);
+		// 转换成 hex 格式
 		if (!k) {
-			setWriteError();
+			if(s) setWriteError();
 			return 0;
 		}
 		if (k & 0x80) {						// it's a capital letter or other character reached with shift
-			_keyReport.modifiers |= 0x02;	// the left shift modifier
+			if(s) _keyReport.modifiers |= 0x02;	// the left shift modifier
+			else _keyReport.modifiers &= ~(0x02);
 			k &= 0x7F;
 		}
 	}
-	
-	// Add k to the key report only if it's not already present
-	// and if there is an empty slot.
-	if (_keyReport.keys[0] != k && _keyReport.keys[1] != k && 
-		_keyReport.keys[2] != k && _keyReport.keys[3] != k &&
-		_keyReport.keys[4] != k && _keyReport.keys[5] != k) {
-		
+
+	if(s){
+		if (_keyReport.keys[0] != k && _keyReport.keys[1] != k &&
+			_keyReport.keys[2] != k && _keyReport.keys[3] != k &&
+			_keyReport.keys[4] != k && _keyReport.keys[5] != k) {
+
+			for (i=0; i<6; i++) {
+				if (_keyReport.keys[i] == 0x00) {
+					_keyReport.keys[i] = k;
+					break;
+				}
+			}
+			if (i == 6) {
+				setWriteError();
+				return 0;
+			}
+		}
+	}
+	else {
 		for (i=0; i<6; i++) {
-			if (_keyReport.keys[i] == 0x00) {
-				_keyReport.keys[i] = k;
-				break;
+			if (0 != k && _keyReport.keys[i] == k) {
+				_keyReport.keys[i] = 0x00;
 			}
 		}
-		if (i == 6) {
-			setWriteError();
-			return 0;
-		}	
+
+	}
+	return 1;
+}
+
+// press() adds the specified key (printing, non-printing, or modifier)
+// to the persistent key report and sends the report.  Because of the way
+// USB HID works, the host acts like the key remains pressed until we
+// call release(), releaseAll(), or otherwise clear the report and resend.
+size_t Keyboard_::press(uint8_t k)
+{
+    auto ret = set(k, true);
+	if(ret) {
+		sendReport(&_keyReport);
 	}
-	sendReport(&_keyReport);
 	return 1;
 }
 
 // release() takes the specified key out of the persistent key report and
 // sends the report.  This tells the OS the key is no longer pressed and that
 // it shouldn't be repeated any more.
-size_t Keyboard_::release(uint8_t k) 
+size_t Keyboard_::release(uint8_t k)
 {
-	uint8_t i;
-	if (k >= 136) {			// it's a non-printing key (not a modifier)
-		k = k - 136;
-	} else if (k >= 128) {	// it's a modifier key
-		_keyReport.modifiers &= ~(1<<(k-128));
-		k = 0;
-	} else {				// it's a printing key
-		k = pgm_read_byte(_asciimap + k);
-		if (!k) {
-			return 0;
-		}
-		if (k & 0x80) {							// it's a capital letter or other character reached with shift
-			_keyReport.modifiers &= ~(0x02);	// the left shift modifier
-			k &= 0x7F;
-		}
+	auto ret = set(k, false);
+	if(ret) {
+		sendReport(&_keyReport);
 	}
-	
-	// Test the key report to see if k is present.  Clear it if it exists.
-	// Check all positions in case the key is present more than once (which it shouldn't be)
-	for (i=0; i<6; i++) {
-		if (0 != k && _keyReport.keys[i] == k) {
-			_keyReport.keys[i] = 0x00;
-		}
-	}
-
-	sendReport(&_keyReport);
 	return 1;
 }
 
 void Keyboard_::releaseAll(void)
 {
 	_keyReport.keys[0] = 0;
-	_keyReport.keys[1] = 0;	
+	_keyReport.keys[1] = 0;
 	_keyReport.keys[2] = 0;
-	_keyReport.keys[3] = 0;	
+	_keyReport.keys[3] = 0;
 	_keyReport.keys[4] = 0;
-	_keyReport.keys[5] = 0;	
+	_keyReport.keys[5] = 0;
 	_keyReport.modifiers = 0;
 	sendReport(&_keyReport);
 }
@@ -335,4 +332,3 @@ size_t Keyboard_::write(const uint8_t *buffer, size_t size) {
 Keyboard_ Keyboard;
 
 #endif
-
diff --git a/src/Keyboard.h b/src/Keyboard.h
index 96882d8..a6a4028 100644
--- a/src/Keyboard.h
+++ b/src/Keyboard.h
@@ -96,6 +96,7 @@ class Keyboard_ : public Print
 {
 private:
   KeyReport _keyReport;
+  size_t set(uint8_t k, bool s);
   void sendReport(KeyReport* keys);
 public:
   Keyboard_(void);
@@ -111,4 +112,3 @@ extern Keyboard_ Keyboard;
 
 #endif
 #endif
-