了解bootloader的实现，请加QQ： 1273623966 （验证填bootloader）；欢迎咨询或定制bootloader；我的博客主页www.cnblogs.com/geekygeek
今年国庆完成了4个bootloader，前面介绍了2个，都是PIC32MZ的USB bootloader， 接着介绍2个PIC24 的USB bootloader, 首先是PIC24 USB CDC bootloader。PIC24 USB CDC bootloader 是我开发给我的PIC24FJ256GB106硬件板子的。
开发环境
1. IDE： MPLABX v4.01
2. Compiler： XC16, v1.11
3. Library&Example: c:/microchip_solutions_v2013-06-15/USB/Device-CDC-Basic Demo
这个PIC24 CDC bootloader 是在MLA_v2013-06-15的USB CDC basic demo的基础上修改而成。bootloader 占用空间从0x400开始， 长度= 0x1C00。 CDC bootloader模拟UART通信，一行一行接收串口发送过来的hex原文，然后对每行的hex原文进行解析，将里面的bin数据烧写到对应的地址上。整个的逻辑实现都在我写的Boot_DoProcess()函数中，函数代码如下。
uint8_t BOOT_DoProcess(uint8_t *buffer, uint16_t byteCount)
{
uint8_t i; uint8_t bcount, recType;
DWORD_VAL pData;
uint8_t retVal = 0;
if (byteCount == 64)
{
return 1;
}
bcount = GetXbyte(buffer[LEN_NIBBLE1_INDEX],buffer[LEN_NIBBLE2_INDEX]); if (!Checksum(buffer, bcount))
{
retVal = 2;
return retVal;
} srcAddress.v[1] = GetXbyte(buffer[ADDRH_NIBBLE1_INDEX],buffer[ADDRH_NIBBLE2_INDEX]);
srcAddress.v[0] = GetXbyte(buffer[ADDRL_NIBBLE1_INDEX],buffer[ADDRL_NIBBLE2_INDEX]);
srcAddress.Val >>= 1;
recType = GetXbyte(buffer[TYPE_NIBBLE1_INDEX],buffer[TYPE_NIBBLE2_INDEX]);
switch(recType)
{
case LINEAR_ADDRESS:
srcAddress.v[3] = GetXbyte(buffer[TYPE_NIBBLE2_INDEX+1],buffer[TYPE_NIBBLE2_INDEX+2]);
srcAddress.v[2] = GetXbyte(buffer[TYPE_NIBBLE2_INDEX+3],buffer[TYPE_NIBBLE2_INDEX+4]);
retVal = 3;
break;
case DATA:
if ((srcAddress.Val >= BOOT_START_ADDRESS) && (srcAddress.Val < APPL_RESET_ADDRESS)) // boot protection, avoid to overlap
{
retVal = 4;
return retVal;
}
eraseAddress.Val = srcAddress.Val;
if ((srcAddress.Val % ERASE_BLOCK) == 0)
{
NVM_EraseBlock(eraseAddress.Val);
}
for (i=0; i < 2*bcount;)
{
pData.byte.LB = GetXbyte(buffer[TYPE_NIBBLE2_INDEX+1+i+0],buffer[TYPE_NIBBLE2_INDEX+1+i+1]);
pData.byte.HB = GetXbyte(buffer[TYPE_NIBBLE2_INDEX+1+i+2],buffer[TYPE_NIBBLE2_INDEX+1+i+3]);
pData.byte.UB = GetXbyte(buffer[TYPE_NIBBLE2_INDEX+1+i+4],buffer[TYPE_NIBBLE2_INDEX+1+i+5]);
pData.byte.MB = GetXbyte(buffer[TYPE_NIBBLE2_INDEX+1+i+6],buffer[TYPE_NIBBLE2_INDEX+1+i+7]);
unsigned int error = NVM_WriteWord(srcAddress.Val, pData.Val);
if ((error & 0x2000) > 0)
{
retVal = 5;
return retVal;
}
error = 0;
srcAddress.Val += 2;
i += 8;
}
//retVal = 1;
break;
case END:
retVal = 6;
break;
}
return retVal;
}
在main.c中ProcessIO()函数中调用Boot_DoProcess(). ProcessIO改动很大，代码如下。
void ProcessIO(void)
{
BYTE numBytesRead;
WORD status;
//Blink the LEDs according to the USB device status
BlinkUSBStatus();
// User Application USB tasks
if((USBDeviceState < CONFIGURED_STATE)||(USBSuspendControl==1)) return; if(buttonPressed)
{
if(stringPrinted == FALSE)
{
if(mUSBUSARTIsTxTrfReady())
{
putrsUSBUSART("Button Pressed -- \r\n");
stringPrinted = TRUE;
}
}
}
else
{
stringPrinted = FALSE;
} if(USBUSARTIsTxTrfReady())
{
numBytesRead = getsUSBUSART(USB_Out_Buffer,64);
if(numBytesRead != 0)
{
BYTE i;
BYTE j;
for(i=0;i<numBytesRead;i++)
{
switch(USB_Out_Buffer[i])
{
case 0x0A:
case 0x0D:
USB_In_Buffer[i] = USB_Out_Buffer[i];
if (!BOOT_Handshake)
{
BOOT_Handshake = 1;
}
else
{
if ((BOOT_RecordSOF == 1) && (BOOT_RecordEOF == 0))
{
BOOT_RecordBuffer[BOOT_RecordCounter++] = USB_Out_Buffer[i];
BOOT_RecordEOF = 1;
for (j=0; j<BOOT_RecordCounter; j++)
{
BOOT_OperationBuffer[j] = BOOT_RecordBuffer[j];
}
BOOT_OperationCounter = BOOT_RecordCounter;
BOOT_RecordLineFlag = 1;
BOOT_RecordSOF = 0;
BOOT_RecordEOF = 0;
BOOT_RecordCounter = 0;
}
}
break;
case ':':
USB_In_Buffer[i] = USB_Out_Buffer[i];
if (BOOT_Handshake)
{
if (!BOOT_RecordSOF)
{
BOOT_RecordBuffer[BOOT_RecordCounter++] = USB_Out_Buffer[i];
BOOT_RecordSOF = 1;
}
}
break;
default:
USB_In_Buffer[i] = USB_Out_Buffer[i];
if ((BOOT_Handshake == 1) && (BOOT_RecordSOF == 1))
{
BOOT_RecordBuffer[BOOT_RecordCounter++] = USB_Out_Buffer[i];
if (BOOT_RecordCounter == BOOT_RECORD_MAX)
{
BOOT_RecordEOF = 1;
for (j=0; j<BOOT_RecordCounter; j++)
{
BOOT_OperationBuffer[j] = BOOT_RecordBuffer[j];
}
BOOT_RecordLineFlag = 1;
BOOT_OperationCounter = BOOT_RecordCounter;
BOOT_RecordSOF = 0;
BOOT_RecordEOF = 0;
BOOT_RecordCounter = 0;
}
}
break;
}
}
putUSBUSART(USB_In_Buffer,numBytesRead);
if (BOOT_RecordLineFlag)
{
if (BOOT_OperationCounter == BOOT_RECORD_MAX)
{
putUSBUSART("XXXXXXXXXXXXXXXX\r\n", 18);
}
else
{
status = BOOT_DoProcess(BOOT_OperationBuffer, BOOT_OperationCounter);
if (status == 6)
{
//TODO Deinitialization
(*((void(*)(void))APPL_RESET_ADDRESS))();
}
else
{
//putUSBUSART("\r", 1);
}
}
BOOT_RecordLineFlag = 0;
}
}
if (!BOOT_Handshake)
{
BOOT_Timeout--;
if (BOOT_Timeout == 0)
{
// TODO Jump to Application
// TODO Deinitialization
(*((void(*)(void))APPL_RESET_ADDRESS))();
}
else if (BOOT_Timeout%20000 == 0)
{
putUSBUSART(".", 1);
}
}
else
{
if (!BOOT_ProgramRequired)
{
BOOT_ProgramRequired = 1;
putUSBUSART("\r\n",2);
}
}
}
CDCTxService();
} //end ProcessIO
整个CDC bootloader就完成了。合着bootloader的Linker script编译完成后，通过PICKit3烧写到硬件板子中。CDC是模拟UART通信，所以通过USB线连接到电脑，电脑可以侦测到COM口。
接着就是测试bootloader的功能了。写了个测试用的应用程序，应用程序地址是从0x2000开始到结束（地址分配参考AN1094）。应用程序合着客制的Linker script编译。测试时，我是通过超级终端发送应用程序的Hex原文。重启目标板，打开超级终端，选择CDC 模拟的COM口，配置成9600-8-none-1. 设置Line delay=40ms. 超级终端窗口出现”..."字符后，窗口中按下回车，菜单栏选择“发送文本文件”， 加载应用程序Hex, ，点击发送。然后就等着烧写完成。（上面贴的都是最终可以使用的完成函数代码，但是在实现过程中，修改几次，特别是测试过程中，发现不少问题，修改代码一一解决之后才最后完成)
以下是烧写步骤：
1. 打开超级终端
2. 重启烧录好CDC bootloader的目标板
3. 超级终端配置，选择CDC emulating后的出现的COM口，设置成9600-8-none-1, 设置Line Delay.
4. 一旦超级终端窗口出现”..."字符，立即发送回车。
5. 点击发送/发送文本文件..., 选择要发送的hex文件。
6. 等待升级完成，CDC bootloader 每接收完一行都会原文返回。