User`s manual

Getting Started With Linux on the LPC3250 OEM Board Page 27
Copyright 2009 © Embedded Artists AB Rev A
• run – execute the commands found in an environment variable.
Below are examples of the commands described above.
uboot> setenv serverip 192.168.0.110
uboot> saveenv
uboot> run mtdboot
4.2.2 Network Related Variables
The u-boot environment contains a number of variables that are network related, i.e., related to
communication over a network. Make sure these variables are correctly setup for your network.
• ethaddr – Specifies the Ethernet/MAC address that will be assigned to the development
board. The address will also be forwarded to the Linux kernel via the ea_ethaddr
argument in the boot argument list, sections 4.3.4, 4.3.5 and 4.3.6 contain example of its
usage. Make sure your board gets a unique address.
• ipaddr – Specifies the IP address that will be assigned to the development board. The
address will be forwarded to the Linux kernel via the ip argument in the boot argument list,
sections 4.3.4, 4.3.5 and 4.3.6 contain example of its usage. Make sure this address is a valid
and unique address on your network. If you would like to use dynamically assigned IP
addresses see section 4.4.
• serverip – This variable specifies the IP address of the TFTP server used when
downloading images using TFTP. Set it to the IP address of the computer running your TFTP
server. See section 3.6.1 for how to obtain the IP address in a Linux distribution.
• netmask – Defines a mask used to divide your network into subnets. On most office and
home networks the netmask is set to 255.255.255.0 which means that the 3 first octets of the
IP address is fixed while the last can vary.
4.2.3 Boot Related Variables
The variables listed below are all related to the boot process.
• bootargs – This variable contains the boot arguments sent to the Linux kernel. It usually
contains settings for the console and where to find the root file system.
• bootcmd – This variable contains the boot command(s) that will be run during auto booting.
• bootdelay – This variable defines the delay in seconds until an autoboot will take place.
Autoboot can be cancelled by hitting any key during boot.
4.3 Booting Options
Setting up a booting option means specifying from which source the Linux kernel should be loaded as
well as specifing where to find the root file system.
4.3.1 Kernel from USB Memory Stick
Most computers today have a USB connection and most operating systems support USB and have
device drivers for USB mass storage devices. This makes it simple to use a USB memory stick to
transfer boot images from the development computer to the development board.
For this purpose the usb and fatload commands are used to access the memory stick and transfer
the images to the development board. In the default environment there is a variable named
loadkernel_usb which illustrates how to load the kernel from a USB memory stick.
Note: If you have problems loading the images from the USB memory stick, please go to
section 4.5.1 and see if that solution solves your problem.