一、?USB烧写NK.BIN流程：
OEMPlatformInit->CheckUSBDownload()->USBDownload()->ecvPacket()->processPacket()->WriteRawImageToBootMedia()->TOC_Write()
->EBOOT_COMMAND_NOTIFY_STARTDOWNLOADING()->OEMPreDownload ()->DownloadImag()->DownloadSignedBin()->OEMReadData()->WriteImageToFlash()->OEMWriteFlash()->WriteFlashNK()->TOC_Write()
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二、烧写（升级）镜像流程：
eboot目录下main.c中：OEMPlatformInit-> download.c中：CheckUSBDownload-> USBInit-> InitOTG-> if(USBIsCableAttached)-> USBDownload
?? USBDownload-> if(IsUSBRequest()==TRUE)-> recvPacket-> processPacket
在processPacket中有很多的处理USB传输过来每帧（0x800=2K）的命令字。每帧前16个字节分别是：
?BytesToDWORD(pRxBuffer,&cmd);
?BytesToDWORD(pRxBuffer+4,&address);
?BytesToDWORD(pRxBuffer+8,&length);
?BytesToDWORD(pRxBuffer+12,&rxChecksum);
且校验和为2K-16个字节后面字节的累加和。函数为：download.c中的CheckSum。
大致流程是：eboot目录下的USB.C中的OTGDEV_RdPktBulkOutEp（）函数里的接收到ATUD->后发送OKUD。然后上位机发送2K字节的每一帧数据。每一帧数据的前16个字节为协议信息。
USB-Monitor下来的前2帧的命令分别是：EBOOT_COMMAND_NOTIFY_STARTDOWNLOADING（07）输出LOG提示信息，然后是：EBOOT_COMMAND_GETVERSION（13）获取EBOOT版本号，第三帧就开始传输NK.BIN.
dragin和210通讯详细流程：
? 0.进入 USBDownload（）
1.上位机发送ATUD四个字节->210回送OKUD四个字节
2.上位机发送Eboot version请求(cmd=EBOOT_COMMAND_GETVERSION)->210回送0x31313030
3.上位机发送cmd=EBOOT_COMMAND_NOTIFY_STARTDOWNLOADING和address=0 ->210回送CheckSum
4.上位机发送cmd=EBOOT_COMMAND_WRITETOMEM（2k帧为 cmd+address+length+checksum+nk.bin）->210回送CheckSum
5.上位机发送cmd=EBOOT_COMMAND_FLASH_BOOTLOADER（dwDLType == 0）->210回送CheckSum
6.上位机发送cmd=EBOOT_COMMAND_OPENSTL->210回送CheckSum
7.上位机发送cmd=EBOOT_COMMAND_NOTIFY_STARTDOWNLOADING 和address=1 ->210回送CheckSum
8.上位机发送cmd=EBOOT_COMMAND_WRITETOMEM（2k帧为 cmd+address+length+checksum+nk.bin）->210回送CheckSum
9.上位机发送cmd=EBOOT_COMMAND_FLASH_BOOTLOADER(dwDLType == 1跟第5步执行不同的操作)->210回送CheckSum
10.退出 USBDownload（）
注：以上是下载bootloader和nk.bin流程? 如果只想下载nk.bin只需要1 2 6 7 8 9其中2也可以省略掉
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三、附dragin烧写工具信息记录：
---------------------------------------------------------------------------------------
Notify Connecting USB(Type : USB SERIAL)
---------------------------------------------------------------------------------------
USB requests to connect is received
Attempting to open ?usb#vid_0547&pid_2720#5&2bf451f8&0&2#{25dbce51-6c8f-4a72-8a6d-b54c2b4fc835}
To open ?usb#vid_0547&pid_2720#5&2bf451f8&0&2#{25dbce51-6c8f-4a72-8a6d-b54c2b4fc835} is success
The end of ENUM
USB device name : 5&2bf451f8&0&2
USBSeral COM port : 0
A device requested to connect
---------------------------------------------------------------------------------------
BOOT VERSION = 11.00
---------------------------------------------------------------------------------------
---------------------------------------------------------------------------------------
Notify Downloading(Type : BOOT,Downloads : 267)
---------------------------------------------------------------------------------------
---------------------------------------------------------------------------------------
Flash image(Type : BOOT,Blocks : 3)
---------------------------------------------------------------------------------------
---------------------------------------------------------------------------------------
Notify Downloading(Type : OS,Downloads : 48896995)
---------------------------------------------------------------------------------------
---------------------------------------------------------------------------------------
Flash Image(Type : OS,Blocks : 187)
---------------------------------------------------------------------------------------
Real Blocks : 1
---------------------------------------------------------------------------------------
Launch image(Launch Address : 0x80028000)
-----------------------------------------------
---------------------------------------------------------------------------------------
Notify Connecting USB(Type : USB SERIAL)
---------------------------------------------------------------------------------------
USB requests to connect is received
Attempting to open ?usb#vid_0547&pid_2720#5&2bf451f8&0&2#{25dbce51-6c8f-4a72-8a6d-b54c2b4fc835}
To open ?usb#vid_0547&pid_2720#5&2bf451f8&0&2#{25dbce51-6c8f-4a72-8a6d-b54c2b4fc835} is success The end of ENUM USB device name : 5&2bf451f8&0&2 USBSeral COM port : 0 A device requested to connect --------------------------------------------------------------------------------------- BOOT VERSION = 11.00 --------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------- Notify Downloading(Type : BOOT,Downloads : 267) --------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------- Flash image(Type : BOOT,Blocks : 3) --------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------- Notify Downloading(Type : OS,Downloads : 48883007) --------------------------------------------------------------------------------------- --------------------------------------------------------------------------------------- Flash Image(Type : OS,Blocks : 187) --------------------------------------------------------------------------------------- Real Blocks : 1 --------------------------------------------------------------------------------------- Launch image(Launch Address : 0x80028000) ---------------------------------------------------------------------------------------
