1.问题

bootloader写成后，需要处理传送过来的.Hex，或者等价的文件的烧录。MicroChip官方并未给出一个.Hex转为.Bin的处理策略。在它的Bootloader代码中，我们可以大致看到它的实现机制，它定义了一组命令。上位机在处理升级时，与Bootloader要通过这组指令进行信息传递。这是一个交互式的协议。如果我们抛开这个交互协议，希望自己处理升级过程，那么，需要对.Hex文件本身进行处理。然后才能让bootloader解析。

2.分析

2.1 Hex文件格式

Microchip给出了这个定义，参见：

MPLAB® IPE Intel HEX File Format | Microchip TechnologyLearn what records are contained within a hex file and where the records are within the file. https://www.microchip.com/en-us/education/developer-help/learn-tools-software/mcu-mpu/mplab-ipe/sqtp-file-format-specification/intel-hex

重点如下：

Hex文件被拆分为一条条记录。
每条记录头部固定，分别是
- Byte0: ":"
- Byte1: 数据字段长度
- Byte2-3:数据要放置到的内存区域地址：两字节，这是英特尔固有的格式MSB，高位前，注意。
- Byte4:这是类型，对PIC而言，只有3种类型：0,1,4
- Byte5开始，是有效载荷。总长度= Byte1
- 最后一个字段是校验和，校验和从Byte1开始，至有效载荷结束。校验和要保证，从Byte1到它自身的值=0.

2.2 字节流分帧解析

//与Hex分帧相关的数据结构
#define FLASH_WRITE_BLOCK 64
#define HEX_MAX_RECORD 16
#define HEX_RECORD_STR_MAX (1+5*2+0x10*2)
struct _HexRecorderFilterObj
{
    uint16_t targetAddr;
    uint8_t write_block[FLASH_WRITE_BLOCK]; //注意類型
    uint8_t write_block_offset;
    uint8_t frame_cache[HEX_RECORD_STR_MAX+1];
    uint8_t frame_cache_offset;
    uint16_t debugCnt[4]; /*line, 0cnt, 1cnt, 4cnt*/
    uint32_t file_len;
}hexRecorderFilterObj;

//Hex分帧数据结构初始化
void HexRecordFilter_Init(void)
{
    //hexRecorderFilterObj.write_block_offset = 0;
    //hexRecorderFilterObj.frame_cache_offset = 0;
    memset(&hexRecorderFilterObj, 0, sizeof(hexRecorderFilterObj));
}

//辅助函数，将缓冲区中相邻的一个Hex字节读出来
//未考虑小写字符，未考虑容错
uint8_t Hex2Byte(uint8_t *buf)
{
    uint8_t ret;
    if((*buf>='0')&& (*buf<='9')) ret = (*buf - '0');
    else ret = (*buf - 'A') + 10;
    buf++;
    ret<<=4;
    if((*buf>='0')&& (*buf<='9')) ret |= (*buf - '0');
    else ret |= (*buf - 'A')+ 10;
    return ret;
}

//这里传入是已经是.hex的一个完整的帧
bool Decode_a_hex_frame(uint8_t *frame, uint32_t len)
{
//:1057E000FFFFFF00FFFFFF00FFFFFF00FFFFFF00C5
    if(Hex2Byte(frame+1)*2+5*2+1 != len) return false;
    hexRecorderFilterObj.file_len += len;
    hexRecorderFilterObj.debugCnt[0]++;
    switch(Hex2Byte(frame+7))
    {
        case 0x01: hexRecorderFilterObj.debugCnt[2]++; break;
        case 0x04: hexRecorderFilterObj.debugCnt[3]++; break;
        case 0x00: hexRecorderFilterObj.debugCnt[1]++; break;
        default: 
            return false;
    }
    return true;
}

//一个统计函数
void PrintHexFileFilterDesc(void)
{
    xlog("total rec:%d, f0:%d,f1:%d,f4:%d; filelen=%d\r\n", 
            hexRecorderFilterObj.debugCnt[0],
            hexRecorderFilterObj.debugCnt[1],
            hexRecorderFilterObj.debugCnt[2],
            hexRecorderFilterObj.debugCnt[3],
            hexRecorderFilterObj.file_len);
}

//顶层函数，传入Hex的分段读入的信息
//已适当考虑容错
HAL_StatusTypeDef HexRecordFilter(uint8_t *buf, uint32_t len)
{
//:1057F00000000000FFFF0000EE2300007F3E0000DD
    do
    {
        if(hexRecorderFilterObj.frame_cache_offset>0)
        {
            if(hexRecorderFilterObj.frame_cache_offset>HEX_RECORD_STR_MAX)
            {
                hexRecorderFilterObj.file_len+=hexRecorderFilterObj.frame_cache_offset;
                hexRecorderFilterObj.frame_cache_offset = 0;
            }
            else if((*buf=='\r') || (*buf == '\n'))
            {
                hexRecorderFilterObj.frame_cache[hexRecorderFilterObj.frame_cache_offset] = 0;
                if(!Decode_a_hex_frame(hexRecorderFilterObj.frame_cache, hexRecorderFilterObj.frame_cache_offset))
                {
                    //return HAL_ERROR;
                }
                hexRecorderFilterObj.file_len++;
                hexRecorderFilterObj.frame_cache_offset = 0;
            }
            else hexRecorderFilterObj.frame_cache[hexRecorderFilterObj.frame_cache_offset++] = *buf;
        }
        else if(*buf == ':')
        {
            hexRecorderFilterObj.frame_cache[0] = *buf;
            hexRecorderFilterObj.frame_cache_offset = 1;
        }
        else
        {
            hexRecorderFilterObj.file_len++;
        }
        buf++;
        len--;
    }while(len>0);
    return HAL_OK;
}