iOS蓝牙开发中的CRC8校验

#pragma mark--CRC8校验
+ (NSString *)crc8_maxin_byteCheckWithHexString:(NSString*)hexString {
    NSString * tempStr = hexString;
    NSArray *tempArray = [self getByteForString:hexString];
//    NSArray  * tempArray = [tempStr componentsSeparatedByString:@" "];//分隔符
    unsigned char testChars[(int)tempArray.count];
    for(int i=0;i<tempArray.count;i++){
        NSString * string = tempArray[i];
        unsigned char fristChar = [self hexHighFromChar:[string characterAtIndex:0]];
        unsigned char lastChar  = [self hexLowFromChar:[string characterAtIndex:1]];
        unsigned char temp = fristChar+lastChar;
        testChars[i] = temp;
    }
    unsigned char res = [self crc8_maxin_checkWithChars:testChars length:(int)tempArray.count];
    return [NSString stringWithFormat:@"%x", res];
}

+(unsigned char)hexHighFromChar:(unsigned char) tempChar{
    unsigned char temp = 0x00;
    switch (tempChar) {
        case 'a':temp = 0xa0;break;
        case 'A':temp = 0xA0;break;
        case 'b':temp = 0xb0;break;
        case 'B':temp = 0xB0;break;
        case 'c':temp = 0xc0;break;
        case 'C':temp = 0xC0;break;
        case 'd':temp = 0xd0;break;
        case 'D':temp = 0xD0;break;
        case 'e':temp = 0xe0;break;
        case 'E':temp = 0xE0;break;
        case 'f':temp = 0xf0;break;
        case 'F':temp = 0xF0;break;
        case '1':temp = 0x10;break;
        case '2':temp = 0x20;break;
        case '3':temp = 0x30;break;
        case '4':temp = 0x40;break;
        case '5':temp = 0x50;break;
        case '6':temp = 0x60;break;
        case '7':temp = 0x70;break;
        case '8':temp = 0x80;break;
        case '9':temp = 0x90;break;
        default:temp = 0x00;break;
    }
    return temp;
}

+(unsigned char)hexLowFromChar:(unsigned char) tempChar{
    unsigned char temp = 0x00;
    switch (tempChar) {
            case 'a':temp = 0x0a;break;
            case 'A':temp = 0x0A;break;
            case 'b':temp = 0x0b;break;
            case 'B':temp = 0x0B;break;
            case 'c':temp = 0x0c;break;
            case 'C':temp = 0x0C;break;
            case 'd':temp = 0x0d;break;
            case 'D':temp = 0x0D;break;
            case 'e':temp = 0x0e;break;
            case 'E':temp = 0x0E;break;
            case 'f':temp = 0x0f;break;
            case 'F':temp = 0x0F;break;
            case '1':temp = 0x01;break;
            case '2':temp = 0x02;break;
            case '3':temp = 0x03;break;
        case '4':temp = 0x04;break;
            case '5':temp = 0x05;break;
            case '6':temp = 0x06;break;
            case '7':temp = 0x07;break;
            case '8':temp = 0x08;break;
            case '9':temp = 0x09;break;
            default:temp = 0x00;break;
            }
    return temp;
    
}

+(char)crc8_maxin_checkWithChars:(unsigned char *)chars length:(int)len{
    unsigned char i;
    unsigned char crc=0x00; /* 计算的初始crc值 */
    unsigned char *ptr = chars;
    while(len--){
        crc ^= *ptr++;
            for(i = 0;i < 8;i++)
                {
                    if(crc & 0x01){
                        crc = (crc >> 1) ^ 0x8C;
                    }else crc >>= 1;
                }
        
    }
    return crc;
    
}

+ (NSArray *)getByteForString:(NSString *)string {
    NSMutableArray *strArr = [NSMutableArray array];
    for (int i = 0; i < string.length/2; i++) {
        NSString *str = [string substringWithRange:NSMakeRange(i * 2, 2)];
        [strArr addObject:str];
        
    }
    return [strArr copy];
    
}