一、字符串转ASCII

字符串其实就是上述ASCII表中的图形栏内容，转换成hex，即变成对应的十六进制数。通常以0123456789ABCDEF，进行转换。找规律：字符 ‘0’ 对应0x30 字符 ‘1’ 对应0x31 字符‘A’ 对应0x41 字符 ‘a’对应 0x61 等这些都是简单，早就知道的。换成C语言则可以这样写：

‘0~9‘ + 0x30

‘A~F’ - ‘A’+10

‘a~f’ - ‘a’+10

void str_to_acsll(uint8_t  *s_inchar, uint8_t s_len, uint8_t  *a_outtxt)
{

    uint8_t size1=0,i=0;
         for( size1=0;size1<s_len; size1++)
        {
            
            if(    s_inchar[size1]>='0' && s_inchar[size1] <= '9')
            {
                a_outtxt[size1] = s_inchar[size1] - 0x30;
            }
            else if(    s_inchar[size1]>='A' && s_inchar[size1] <= 'F')
            {
                a_outtxt[size1] = s_inchar[size1] - 'A'+10;
            }
            else if(    s_inchar[size1]>='a' && s_inchar[size1] <= 'f')
            {
                a_outtxt[size1] = s_inchar[size1] - 'a'+10;
            }

        }
     for( size1=0,i=0;size1<=s_len; size1++,i++)
     {
            a_outtxt[i]=(a_outtxt[size1]<<4)|a_outtxt[++size1];            
     }
      a_outtxt[i] = '\0'; 
}

二、字符串转hex

这个是用于把字符串占两个字节的，合成为一个hex使用。比如:“FF” -> 0xff 字符串占用的是两个字节的数其实是一个hex的，那么就要位移合成。

uint16_t stringtohex(uint8_t *buf, uint8_t * format, uint16_t us_length)
{
    uint8_t tempcode;
    uint16_t uslength = us_length * 2,us_count = 0,us_data;

    for(us_data = 0;us_count < uslength; us_count += 2,us_data++)
    {
        tempcode = format[us_data] >> 4;

        if(tempcode <= 9)
        {
            buf[us_count] = tempcode + '0';
        }
        else
        {
            buf[us_count] = tempcode - 10 + 'A';
        }
        tempcode = format[us_data] & 0X0F;
        if(tempcode <= 9)
        {
            buf[us_count+1] = tempcode + '0';
        }
        else
        {
            buf[us_count+1] = tempcode - 0X0A + 'A';
        }
    }
    buf[uslength] = '\0';
    return uslength;
}

三、16进制整数转字符串

static void hex_to_str(uint8_t *source, uint32_t len, uint8_t *target)
{
    uint8_t ddl, ddh;
    uint32_t i;

    for (i = 0; i < len; i++)
    {
        ddh = ('0' + source[i] / 16);
        ddl = ('0' + source[i] % 16);

        if (ddh > '9')
            ddh = (ddh + ('a' - '9' - 1));
        if (ddl > '9')
            ddl = (ddl + ('a' - '9' - 1));

        target[i * 2] = ddh;
        target[i * 2 + 1] = ddl;
    }
    target[len] = '\0';
}