需要将数据(字节值转换为十六进制字符和十六进制字符作为ASCII字符)

Question

工作:我从内存中读取一个字节(EEPROM/FLASH等)，然后我想将这个字节作为十六进制值的一个ascii字符发送到计算机。例如，我从内存中读取160，内存中的十六进制是0xA0，现在我想以'A‘和'0’( 0x41和0x30)的形式发送这个数字，为此，我在MPLAB IDE中使用了这种类型的c代码，

    //Here is the code for Parity:
    uint8_t unAddParitytoByte(uint8_t unByte)
    { 
           uint8_t unNumberofOnes = 0;
           for(uint8_t unI = 0x80; unI ; unI>>=1)
           {
                 if((unByte & unI) != 0)
                {
                     unNumberofOnes++;
                }
          }
          if((unNumberofOnes%2) == 0)
          {
                  return unByte;
          }
          else
          {
               return (unByte|BIT7);
          }
    }
    void vSendByteToSoftware(uint8_t unDataByte)
    {
        uint8_t unTemp = 0, unHalfByte = 0;
        unTemp = (unDataByte >> 4) & 0x0F;
        unHalfByte = unReturnASCII(unTemp);
    /*Ignore vSerialTransmitCharacter(); as it transmit through uart and unAddParitytoByte(); to add 8th bit parity*/
        vSerialTransmitCharacter(unAddParitytoByte(unHalfByte)); 
        unBCCByte ^= unAddParitytoByte(unHalfByte);
        unTemp = unDataByte & 0x0F;
        unHalfByte = unReturnASCII(unTemp);
        vSerialTransmitCharacter(unAddParitytoByte(unHalfByte));
        unBCCByte ^= unAddParitytoByte(unHalfByte);
    }
    uint8_t unReturnASCII(uint8_t unNibble)
    {
         uint8_t unChar = 0;
         switch(unNibble)
         {
            case 0:
                 unChar = '0';
                 break;
            case 1:
                 unChar = '1';
                 break;
            case 2:
                 unChar = '2';
                 break;
            case 3:
                 unChar = '3';
                 break;
            case 4:
                 unChar = '4';
                 break;
            case 5:
                 unChar = '5';
                 break;
            case 6:
                 unChar = '6';
                 break;
            case 7:
                 unChar = '7';
                 break;
            case 8:
                 unChar = '8';
                 break;
            case 9:
                 unChar = '9';
                 break;
            case 10:
                 unChar = 'A';
                 break;
            case 11:
                 unChar = 'B';
                 break;
            case 12:
                unChar = 'C';
                break;
            case 13:
                unChar = 'D';
                break;
            case 14:
                unChar = 'E';
                break;
            case 15:
                unChar = 'F';
                break;
            default:
                break;
        }
        return unAddParitytoByte(unChar);
    }
    vSendByteToSoftware(unReadBytesfromTargetFlash());

希望这是可以理解的。问题:我关心的是，我有一个频率为3.6864MHz的控制器，而且我必须在大约100万字节或更多字节上执行这个操作，所以这很费时。

，我在想，对于每一个字节，是否有先进和最快的方法来处理这个过程，从而使我的操作非常快？。

注意：(波特率为115200，速度相当快，我想要处理字节的速度，而不是发送它们的时间)。

Answer 1

每个半字节都有16个可能的值，它们是顺序的，从零开始。这是查找表的理想选择。

    uint8_t const ascii_hex[16] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};

    void vSendByteToSoftware(uint8_t unDataByte)
    {
        uint8_t unTemp = 0, unHalfByte = 0;
        unTemp = (unDataByte >> 4) & 0x0F;
        unHalfByte = ascii_hex[unTemp];
    /*Ignore vSerialTransmitCharacter(); as it transmit through uart and unAddParitytoByte(); to add 8th bit parity*/
        vSerialTransmitCharacter(unAddParitytoByte(unHalfByte)); 
        unBCCByte ^= unAddParitytoByte(unHalfByte);
        unTemp = unDataByte & 0x0F;
        unHalfByte = ascii_hex[unTemp];
        vSerialTransmitCharacter(unAddParitytoByte(unHalfByte));
        unBCCByte ^= unAddParitytoByte(unHalfByte);
    }

Update：由于您正在传输的字符仅限于16个字符，因此您可以预先计算这16个字符的奇偶校验，然后使用查找表获取奇偶校验值。(请再次检查我是否正确地完成了奇偶校验计算。)

uint8_t const ascii_hex[16] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};
uint8_t const ascii_hex_with_parity[16] = { 0x30, 0xB1, 0xB2, 0x33, 0xB4, 0x35, 0x36, 0xB7, 0xB8, 0x39, 0x41, 0x42, 0xC3, 0x44, 0xC5, 0xC6};

void vSendByteToSoftware(uint8_t unDataByte)
{
    uint8_t unTemp = 0, unHalfByte = 0;
    unTemp = (unDataByte >> 4) & 0x0F;
    unHalfByte = ascii_hex[unTemp];
/*Ignore vSerialTransmitCharacter(); as it transmit through uart and unAddParitytoByte(); to add 8th bit parity*/
    vSerialTransmitCharacter(unAddParitytoByte(unHalfByte)); 
    unBCCByte ^= ascii_hex_with_parity[unTemp];
    unTemp = unDataByte & 0x0F;
    unHalfByte = ascii_hex[unTemp];
    vSerialTransmitCharacter(unAddParitytoByte(unHalfByte));
    unBCCByte ^= ascii_hex_with_parity[unTemp];
}