unsigned char data[4]={0xFA,0xDB,0x02,0xcc};
    char result[2*4+1]={0};
    for(int i=0; i<sizeof(data)/sizeof(data[0]); i++)
    {
        sprintf(result+2*i,"%02X",data[i]); // %X结果为大写，%x结果为小写

    }
    cout<<result<<endl;

res:

FADB02CC