Setting up ZyXEL NWD2105 for CentOS-5 and Ubuntu (10.04)

driver info page: http://www.wikidevi.com/wiki/ZyXEL_NWD2105

driver installation guide: http://eimer.ch/nwd2105.html 

$ cd 2011_0107_RT3070_RT3370_Linux_STA_v2.5.0.1_DPO/

$ make; make install

$ edit /etc/Wireless/RT2870STA/RT2870STA.dat for
    SSID=_YOUR_AP's_SSID_
    NetworkType=Infra   
    WirelessMode=5
    Channel=0
    AuthMode=OPEN
    EncrypType=WEP
    DefaultKeyID=1
    Key1Type=1    # (for ASCII key)
    Key1Str=_YOUR_ASCII_PASSWORD_
$ refer to README_STA_usb for further parameter details

For CentOS-5:

$ edit /etc/modprobe.conf; append "alias ra0 rt3070sta" to it.
$ edit /etc/sysconfig/network-scripts/ifcfg-ra0:
   DEVICE='ra0'
   ONBOOT='yes'
   BOOTPROTO='dhcp'
$ edit /etc/sysconfig/network-scripts/ifup-wireless
   comment out the following two lines:
       line-65: iwconfig $DEVICE key off
       line-98: iwconfig $DEVICE essid any >/dev/null 2>&1

$ /sbin/reboot # to check if the wireless is working after reboot

For Ubuntu (10.04):

* edit /etc/modprobe.d/wireless.conf; add "alias ra0 rt3070sta" to it.
* edit /etc/network/interface:
        auto lo
        iface lo inet loopback
        auto wlan0
        iface wlan0 inet dhcp
* /etc/init.d/networking restart
* /sbin/reboot # to check if the wireless is working after reboot

 

負整數 - 正整數 = 正整數？

「負整數 - 正整數 = 正整數」在數學上是不正確的，但在計算機上是可能的，詳細原因可以從布林代數的整數加減法的推算得到解答，這裡列舉一個可能的情形：

• a, b, c 均是 32-bit 的整數 (signed integer)  
• a = 2147483647
• b = -2147483648
• c = b - a = 1
• 十進位表示：
  c(1) = b(-2147483648) - a(2147483647)
• 十六進位表示：
  c(0x00000001) = b(0x80000000) - a(0x7FFFFFFF)

以下是對映的 C 程式：

void main(void)
{
    int32_t a;
    int32_t b;
    int32_t c;

    a = 0x7FFFFFFF;
    printf ("a(%d)\n", a);
    b = a+1;
    printf ("b(%d)\n", b);
    c = b - a;
    printf ("c(%d) = b(%d) - a(%d)\n", c, b, a);
    printf ("c(0x%08X) = b(0x%08X) - a(0x%08X)\n", c, b, a);
}

Ubuntu 10.04 LTS for DELL Vostro 3350

I got my newly arrived Dell vostro 3350 on Jun 29, 2011. I love its anti-glare LCD screen as well as the back-lit keyboard. It was smooth to install Ubuntu 10.04 LTS on it. Everything works after rebooting, except that the LCD resolution was incorrect; also, the Wireless LAN was not working.

Here are my workaround to have them work correctly:

VGA:

• Install backport-maverick kernel for LCD resolution detection (1366x768)
  sudo apt-get install linux-image-generic-pae-lts-backport-maverick \
  linux-headers-generic-pae-lts-backport-maverick
• Reboot
  

Wireless LAN:

• Build the compat-wireless device driver manually for backport-maverick kernel
• Here's the Building and Installing steps
  cd compat-wireless-`date -I`; make; sudo make install
  
• Reboot