Question

工作：我正从内存中读取一个字节（EEPROM / FLASH等）然后我想将此字节发送到计算机而不是实际值，而是作为其十六进制值的ascii字符。例如我从内存中读取160，这是十六进制的0xA0，现在我想发送这个数字不是160，而是'A'和'0'（它们是0x41和0x30），为此我在MPLAB IDE中使用这种类型的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());

我希望这是可以理解的。问题：我担心的是我有一个频率为3.6864MHz的控制器，我必须在大约1M字节或更多字节上执行此操作，因此耗费了大量时间。

我想知道是否每个字节都有先进且最快的方法来处理这个过程，这可以使我的操作非常快？

注意:(波特率是115200，非常快，我希望处理字节的速度，而不是发送它们的时间。）

Answer 1

每个半字节有16个可能的值，这些值是顺序的，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);
    }

<强>更新：由于您传输的字符限制为16个字符集，因此您可以预先计算这16个字符的奇偶校验，然后使用查找表来获取奇偶校验值。（请仔细检查我是否正确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];
}

需要转换数据（字节值为十六进制和十六进制字符为ASCII字符）

1 个答案: