不能存数值，写进去之后用ascII都转成字符了，该怎么改？

        u8 bt[]={25,26};
        res=f_mkdir("dianliu");//½¨á￠Îļt¼D
        res=f_open(&f_txt,"0:/dianliu/dianli2.txt",FA_READ | FA_WRITE | FA_CREATE_ALWAYS | FA_OPEN_ALWAYS | FA_CREATE_NEW);
        f_lseek(&f_txt,0);
        f_write(&f_txt,&bt[0],1,(UINT*)&br);
        f_close(&f_txt);