Connect to a modified router
Summary
This will explain how to connect to the serial ports on a modified LinkSys WRT54G using serial communication software such as the open source Kermit.
Before Starting
Expose a serial port on the router
You must have successfully modified a LinkSys WRT54G to expose at least its first serial port in such a way that you can connect it to another machine with serial communications software. If you have not done so yet, please see HOWTO:Modify the Linksys hardware
Acquire serial communication software
There is a freely available software package for serial communication on almost every major platform. A solid open source suite of communication software known as Kermit has served us well as a method of communicating with the WRT54GL. C-Kermit is the UNIX compatible implementation, and a Windows version, Kermit 95, is available as well.
Alternatively, if you are building multiple backends to be made available as a pool, our suite of XINU Console Tools includes a basic serial console utility called tty-connect.
Steps to Connect to the Router
Task One: Connect Serial (& Optionally Network) Cable(s)
Ensure that the connection is going from UART0 (the first serial port--you did label them didn't you?) as this is where the console will be running. If you are connecting a standard PC serial port (a DTE) to your router, use a straight serial cable. Other arrangements may require a Null Modem; check your transmit/receive line polarities to be sure.
Also, because the goal is to upload custom code to the router, it would be a good idea to connect the router to your network by wiring it up via one of the numbered LAN ports on the back of the router (NOT the Internet/WAN port).
Task Two: Configure your Serial Communication Software
The connection used by the router's serial port is fairly standard: 115200bps, with 8 data bits, no parity bit, and 1 stop bit, or 8N1. Set your software to connect using these settings.
Task Three: Power up the Router
Yes, that means plug it in.
With serial communications software listening, you should see something like the following output:
CFE version 1.0.37 for BCM947XX (32bit,SP,LE)
Build Date: Mon Nov 14 18:06:25 CST 2005 (root@localhost.localdomain)
Copyright (C) 2000,2001,2002,2003 Broadcom Corporation.
Initializing Arena
Initializing Devices.
No DPN
et0: Broadcom BCM47xx 10/100 Mbps Ethernet Controller 3.90.37.0
CPU type 0x29008: 200MHz
Total memory: 16384 KBytes
Total memory used by CFE: 0x80300000 - 0x803A39C0 (670144)
Initialized Data: 0x803398D0 - 0x8033BFE0 (10000)
BSS Area: 0x8033BFE0 - 0x8033D9C0 (6624)
Local Heap: 0x8033D9C0 - 0x803A19C0 (409600)
Stack Area: 0x803A19C0 - 0x803A39C0 (8192)
Text (code) segment: 0x80300000 - 0x803398D0 (235728)
Boot area (physical): 0x003A4000 - 0x003E4000
Relocation Factor: I:00000000 - D:00000000
Boot version: v3.7
The boot is CFE
mac_init(): Find mac [00:18:39:6F:78:15] in location 0
Nothing...
eou_key_init(): Find key pair in location 0
The eou device id is same
The eou public key is same
The eou private key is same
Device eth0: hwaddr 00-18-39-6F-78-15, ipaddr 192.168.1.1, mask 255.255.255.0
gateway not set, nameserver not set
Loader:raw Filesys:raw Dev:flash0.os File: Options:(null)
Loading: ...... 1601536 bytes read
Entry at 0x80001000
Closing network.
Starting program at 0x80001000
CPU revision is: 00029008
Primary instruction cache 16kb, linesize 16 bytes (2 ways)
Primary data cache 8kb, linesize 16 bytes (2 ways)
Linux version 2.4.20 (root@localhost.localdomain) (gcc version 3.2.3 with Broadcom modifications)
...
(snip)
...
Hit enter to continue...
Pressing enter will give you a root shell:
BusyBox v0.60.0 (2005.11.14-09:45+0000) Built-in shell (msh) Enter 'help' for a list of built-in commands. #
Task Four: Access the Common Firmware Environment CLI
This will be filled in, but here's the basics:
- Make sure boot_wait is on (this should be added to the Install OpenWRT HOWTO)
- Reboot the router (
rebootor power cycle). - Hit CTRL+C on your serial console.
- You're in.
