![\"Routerboard](\"http:\/\/jacksontech.net\/wp-content\/uploads\/2014\/07\/routerboard1.jpg\")
<\/a>Routerboard 411 – with professional antenna attachment!<\/p><\/div>\n
The specs:<\/p>\n
- \n
- 300MHZ AR7130 CPU<\/li>\n
- 32MB RAM<\/li>\n
- 4MB NAND Flash<\/li>\n
- AR5413 802.11a\/b\/g MiniPCI wireless radio<\/li>\n
- Serial port<\/li>\n
- 1 Fast Ethernet port (supports PoE over non-data pairs, 10-28V)<\/li>\n
- MicroTek RouterOS<\/li>\n
- Professional low-gain adjustable wifi antenna (Oh, no, wait–that’s aftermarket!)*<\/li>\n<\/ul>\n
The cause of the board’s failure is evident in the photos; four of the five capacitors on the board have vented. As a result, the board has trouble booting up with some power supplies and is very picky about voltages. However, I found one power brick that provides just the right voltage for it to boot up without errors. (I’m waiting on replacement capacitors to solder in.)<\/p>\n
Once I got the router to boot, I tried logging in to the admin panel. However, the default RouterOS username\/password combo didn’t work, and I’m not a huge fan of RouterOS anyhow, so I decided to put OpenWRT on the device for a test run. OpenWRT is a Linux-based router firmware distribution. The Routerboard is one of the many devices supported by OpenWRT.<\/a><\/p>\n
I began by gaining access to the router’s bootloader, which behaves much like the BIOS in a computer. The bootloader is stored in a section of the router’s flash memory and is the first code that runs when the router is powered on. Most routers offer access to the bootloader via a serial cable, although very few have an actual serial port like the Routerboard–the other router I’m working on at the moment has a 4-pin serial header on the circuit board. More on that in another post. Since this router has a serial port, all I needed was a cable and a null-modem adapter, which swaps the transmit and receive lines.<\/p>\n
My serial cable is a cheap USB->Serial adapter. When plugged in, Linux produces the device \/dev\/ttyUSB0<\/strong>. To talk to the router, I used GNU Screen, which is secretly a serial console. The command is as follows:<\/p>\n
screen \/dev\/ttyUSB0 115200<\/pre>\n
115200 is the router’s baud rate. This is specific to certain manufacturers, although 115200 and 9600 are common. Firing it up and then plugging in the router, this appears:<\/p>\n
![\"Bootloader\"](\"http:\/\/jacksontech.net\/wp-content\/uploads\/2014\/07\/routerboard1.png\")
<\/a>Bootloader<\/p><\/div>\n
Pressing a key brings up a menu with various settings:<\/p>\n
![\"Settings](\"http:\/\/jacksontech.net\/wp-content\/uploads\/2014\/07\/routerboard2.png\")
<\/a>Settings menu<\/p><\/div>\n
…from here, I chose Ethernet as a boot device:<\/p>\n
![\"routerboard3\"](\"http:\/\/jacksontech.net\/wp-content\/uploads\/2014\/07\/routerboard3.png\")
<\/a><\/p>\nNow, instead of loading from the NAND flash memory, the router will try to load firmware from the network via TFTP, which means we need a TFTP server! Since my laptop had dnsmasq on it, I used that. I was too lazy to write a configuration file. Instead, I ran it from the command line:<\/p>\n
dnsmasq --tftp-root=\/tftpboot --enable-tftp --dhcp-boot=boot.bin --dhcp-range=192.168.100.25,192.168.100.60 -d<\/pre>\n
I don’t know if the dhcp-range is necessary; it may not be. It worked the first time I tried it, so I didn’t experiment with the dnsmasq command line. Note that by default the router appears to use BOOTP; if you’re using something other than dnsmasq, you may need to change this to DHCP in the “boot protocol” menu of the bootloader.<\/p>\n
Note that you’ll need to either add a firewall exception for DHCP\/TFTP or, if you’re impatient, just disable it entirely. In addition, you’ll need to give your network interface a static IP address on the appropriate netblock. I chose 192.168.100.1.<\/p>\n
Now dnsmasq is running and is ready to serve up the file boot.bin from \/tftpboot to any device that requests it on bootup. What is boot.bin? It’s OpenWRT itself.<\/p>\n
I decided to build OpenWRT from source because 1) I was bored and 2) I wanted the experience. It turns out, it’s very easy. The OpenWRT wiki has several pages on building OpenWRT from source. Unfortunately, the documentation is split into multiple pages and some of them contradict each other. Here’s a good place to start.<\/a> My workflow went something like this:<\/p>\n
- \n
- Fetch the OpenWRT source and install prerequisites.<\/a><\/li>\n
- Update<\/em> the feeds<\/li>\n
- Install<\/em> only the feed I needed (luci)<\/li>\n
- Run make menuconfig<\/strong><\/li>\n
- Use the convenient “Disable Unnecessary Packages” script here<\/a> (scroll down) so you don’t build everything.<\/li>\n
- Run make menuconfig<\/strong> again<\/li>\n
- Build it<\/li>\n<\/ol>\n
In detail:<\/p>\n
1. Fetch source and prerequisites<\/h1>\n
Easy. Follow the directions. You’ll want Attitude Adjustment or trunk.<\/p>\n
2. Update the feeds<\/h1>\n
Also easy. Follow the directions.<\/p>\n
3. Install necessary <\/em>feeds<\/h1>\n
What feeds are necessary<\/em>? The only feed I found to be necessary was “luci”. This is the web GUI for OpenWRT. You probably won’t be very happy without it. Install it using the feeds<\/strong> scripts.<\/p>\n
4. Run make menuconfig<\/em><\/h1>\n
And this is where we configure a billion options! Actually, just a few. Use the keyboard arrows to navigate, Enter to go into a submenu, Spacebar to toggle between selections, and Esc to go back. Entries with a —> are submenus. You’ll want to set the following:<\/p>\n
- \n
- Target: Atheros AR7xxx\/AR9xxx<\/li>\n
- Subtarget: Devices with NAND flash (mostly Microtek)<\/li>\n
- Target Profile: Atheros WiFi (ath5k)<\/li>\n<\/ul>\n
Uncheck the following:<\/p>\n
- \n
- Build the OpenWRT SDK<\/li>\n
- Build the OpenWRT based toolchain<\/li>\n<\/ul>\n
Under image configuration, select “ramdisk”. (At least, that’s what I did–I wanted to test OpenWRT BEFORE flashing it.)<\/p>\n
Keep pressing escape until it asks you to save, and tell it to save the information. This puts the configuration into a file called .config.<\/p>\n
5. Run the “disable unnecessary packages” script<\/h1>\n
- Update<\/em> the feeds<\/li>\n
- Fetch the OpenWRT source and install prerequisites.<\/a><\/li>\n