diff --git a/AT32F425/src/CSL/AT32F425_USB_Lib/usbd_sdr.c b/AT32F425/src/CSL/AT32F425_USB_Lib/usbd_sdr.c
index d0b58a9..35745f9 100644
--- a/AT32F425/src/CSL/AT32F425_USB_Lib/usbd_sdr.c
+++ b/AT32F425/src/CSL/AT32F425_USB_Lib/usbd_sdr.c
@@ -80,6 +80,14 @@ static usb_sts_type usbd_get_descriptor(usbd_core_type *udev)
     case USB_DESCIPTOR_TYPE_CONFIGURATION:
       desc = udev->desc_handler->get_device_configuration();
       break;
+
+#ifndef DAP_FW_V1
+    usbd_desc_t *get_bos_descriptor(void);
+    case DESC_BOS:
+      desc = get_bos_descriptor();
+      break;
+#endif
+
     case USB_DESCIPTOR_TYPE_STRING:
     {
       uint8_t str_desc = (uint8_t)udev->setup.wValue;
@@ -351,7 +359,21 @@ usb_sts_type usbd_device_request(usbd_core_type *udev)
 {
   usb_sts_type ret = USB_OK;
   usb_setup_type *setup = &udev->setup;
-  if((setup->bmRequestType & USB_REQ_TYPE_RESERVED) != USB_REQ_TYPE_STANDARD)
+
+#ifndef DAP_FW_V1
+  extern uint8_t MS_OS_20_DescriptorSet[];
+  if((setup->bmRequestType & USB_REQ_TYPE_RESERVED) == USB_REQ_TYPE_VENDOR)
+  {
+    if((setup->bRequest == WINUSB_VENDOR_CODE) && ((setup->wIndex & 0xFF) == 7))
+      usbd_ctrl_send((usbd_core_type *)udev, MS_OS_20_DescriptorSet, MIN(setup->wLength, MS_OS_20_DescriptorSet[8] | (MS_OS_20_DescriptorSet[9] << 8)));
+    else
+      usbd_ctrl_unsupport((usbd_core_type *)udev);
+    
+    return ret;
+  }
+#endif
+
+  if((setup->bmRequestType & USB_REQ_TYPE_RESERVED) == USB_REQ_TYPE_CLASS)
   {
     udev->class_handler->setup_handler(udev, &udev->setup);
     return ret;
diff --git a/AT32F425/src/descriptor.c b/AT32F425/src/descriptor.c
index 9d80a46..c098507 100644
--- a/AT32F425/src/descriptor.c
+++ b/AT32F425/src/descriptor.c
@@ -379,16 +379,16 @@ static void int_to_unicode(uint32_t value , uint8_t *pbuf , uint8_t len)
 
 
 
-uint8_t BOS_Descriptor[] =
+ALIGNED_HEAD uint8_t BOS_Descriptor[] ALIGNED_TAIL =
 {
 	5,
-	0x0F,
+	DESC_BOS,
 	5+20+8, 0,					// wTotalLength
 	1,							// bNumDeviceCaps
 	
 	/*** MS OS 2.0 descriptor platform capability descriptor ***/
 	28,
-	0x10,
+	DESC_CAPABILITY,
 	5,							// bDevCapabilityType: PLATFORM (05H)
 	0x00,
 	0xDF, 0x60, 0xDD, 0xD8,		// PlatformCapabilityUUID: MS_OS_20_Platform_Capability_ID (D8DD60DF-4589-4CC7-9CD2-659D9E648A9F)
@@ -402,6 +402,17 @@ uint8_t BOS_Descriptor[] =
     0x00,                 		// bAltEnumCmd
 };
 
+usbd_desc_t *get_bos_descriptor(void)
+{
+	static usbd_desc_t bos_descriptor =
+	{
+		sizeof(BOS_Descriptor),
+		BOS_Descriptor
+	};
+	
+	return &bos_descriptor;
+}
+
 
 #define MS_OS_20_SET_HEADER_DESCRIPTOR        0x00
 #define MS_OS_20_SUBSET_HEADER_CONFIGURATION  0x01
@@ -413,7 +424,7 @@ uint8_t BOS_Descriptor[] =
 #define MS_OS_20_FEATURE_CCGP_DEVICE          0x07
 #define MS_OS_20_FEATURE_VENDOR_REVISION      0x08
 
-uint8_t MS_OS_20_DescriptorSet[] = 
+ALIGNED_HEAD uint8_t MS_OS_20_DescriptorSet[] ALIGNED_TAIL = 
 {
 	/*** Microsoft OS 2.0 Descriptor Set Header ***/
 	10, 0,
diff --git a/AT32F425/src/hid_transfer.h b/AT32F425/src/hid_transfer.h
index ae21f4e..da3a158 100644
--- a/AT32F425/src/hid_transfer.h
+++ b/AT32F425/src/hid_transfer.h
@@ -2,11 +2,11 @@
 #define __HID_TRANSFER_H__
 
 
-#define USBD_VID	0x0416
+#define USBD_VID	0x2E3C
 #ifdef DAP_FW_V1
 #define USBD_PID    0x5021
 #else
-#define USBD_PID    0x7687
+#define USBD_PID    0x7021
 #endif
 
 
@@ -26,8 +26,6 @@
 #define CDC_BULK_OUT_SZ   	64
 
 
-#define WINUSB_VENDOR_CODE	0x34
-
 
 uint8_t usbd_hid_process(void);
 
diff --git a/AT32F425/src/main.c b/AT32F425/src/main.c
index eeca533..d2a8d7c 100644
--- a/AT32F425/src/main.c
+++ b/AT32F425/src/main.c
@@ -7,6 +7,12 @@
 #include "hid_transfer.h"
 
 
+/* 在 Option 弹窗的 C/C++ 页中：
+   定义 DAP_FW_V1：   生成 CMSIS-DAP v1 固件，使用 HID 传输协议
+   不定义 DAP_FW_V1： 生成 CMSIS-DAP v2 固件，使用 WINUSB 传输协议
+*/
+
+
 otg_core_type Otg;
 
 
diff --git a/AT32F425/src/usb_conf.h b/AT32F425/src/usb_conf.h
index c9cad39..5474afb 100644
--- a/AT32F425/src/usb_conf.h
+++ b/AT32F425/src/usb_conf.h
@@ -24,6 +24,13 @@
 
 
 
+#define DESC_BOS            0x0F
+#define DESC_CAPABILITY     0x10
+
+#define WINUSB_VENDOR_CODE	0x34
+
+
+
 void usb_delay_ms(uint32_t ms);
 
 
diff --git a/README.md b/README.md
index 3a21ea9..7a20d5b 100644
--- a/README.md
+++ b/README.md
@@ -4,6 +4,10 @@ DAPLink (CMSIS-DAP) porting to Artery AT32F425, WCH CH32V203 and WCH CH32V305.
 ## DAPLink-AT32F425
 DAPLink (CMSIS-DAP) based on Artery AT32F425 (support crystal-less USB), supports SWD, JTAG and CDC.
 
+On C/C++ page of Keil Option Window:
+* Define `DAP_FW_V1`: generate CMSIS-DAP V1 firmware, using HID transport protocol.
+* Do not define `DAP_FW_V1`: Generate CMSIS-DAP V2 firmware, using WINUSB transfer protocol.
+
 ### Pin map
 |  FUNC    | Pin   |
 |  :----   | :---- |