ADS U-boot User`s Manual Applied Data Systems
Contents
1. 3 Booting from external media This section describes how to boot your system from external media without modifying the on board flash When booting from external media U boot loads a Linux kernel directly from external media into RAM instead of loading it from the on board flash chips ADS systems can be booted from compact flash cards in either a compact flash slot or a PCMCIA slot with an adapter 3 Systems with an MMC slot can also be booted from MMC cards When booting from external media you have many options for your root filesystem including ramdisks NFS servers and filesystems on a USB hard drive or Microdrive 3 1 Booting a ramdisk from CF or MMC To boot a Linux using a ramdisk as the root filesystem follow these steps 1 Place a kernel zImage and ramdisk ramdisk gz on your compact flash or MMC card 2 Place the U boot start txt on your card 3 Create a root_config txt on your card with the following contents 3If your board is equipped with both a PCMCIA and a CF slot only the PCMCIA slot slot 0 can be used with U boot ADS document 110010 40011 August 11 2005 Page 2 Applieddata net imbedded Computer Systems ADS U boot Bootloader Manual images_to_dram zImage ramdisk gz setenv root_args rw root dev ram initrd INITRD 5m ramdisk_size 12288 setenv boot linux bootm zImage_buffer 4 Insert your card into the board and apply power to boot your system Note It is not nece2. U boot will execute the command hw _config prior to loading and running Linux Example lines for hw_config txt setenv message echo hw_config txt example only do not use setenv vidclkdiv mw 0x80930084 0x0000c205 setenv pixelmode mw 0x80030054 0x0000140c setenv scrnlines mw 0x80030030 0x000001E0 setenv vlinestep mw 0x80030038 0x00000140 setenv hclktotal mw 0x80030010 0x0000031f setenv hactstrtstop mw 0x80030018 0x001F029F too many to fit on a single command line setenv hw1 run message vidclkdiv pixelmode scrnlines vlinestep setenv hw2 run hclktotal hactstrtstop run all of them setenv hw_config run hwi hw2 Using this format for hw_config txt allows you to easily split up the file into multiple lines and keep the file easy to read 8 Advanced U boot configuration 8 1 How to reprogram upgrade U boot The default U boot environment shipped with ADS systems contains several scripts that can be used to re program the U boot bootloader to a new version To re program U boot follow these steps 1 Place the new u boot bin file on a CF or MMC card Warning The u boot bin file MUST contain a valid version of U boot for your ADS board If u boot bin is not a valid bootloader or contains bugs using it can render your board inoperable If you have downloaded an updated u boot bin from the ADS support web site double check to be sure you have downloaded the proper file for your model board Also you should use md5 to
3. NFS server for any diskless system such as this you must export the filesystem with the no_root_squash option Since this option is a potential security risk to the NFS server you should take appropriate security precautions on your network 4Flash memory cells have a limited number of write erase cycles and are not suitable for use as swap space ADS document 110010 40011 August 11 2005 Page 4 Applieddata net imbedded Computer Systems ADS U boot Bootloader Manual 3 5 Booting a kernel from external media using flash as the root filesystem You can use an existing flash filesystem a JFFS2 CRAMFS etc that you have already programmed into on board flash as your root even when loading the kernel from external media This is especially useful for testing a new kernel as you do not need to reprogram your flash To boot your board in this fashion use the same root_config txt that you used when programming the flash filesystem but replace the images_to_flash line with the line images_to_dram zImage It is not necessary to have the flash filesystem image on the external media Only the kernel and the U boot files are needed 4 Programming a kernel and root filesystem into on board flash 4 1 How installation works U boot installs a kernel and root filesystem into on board flash by erasing the flash partition and writing the image into the flash chips The flash programming process is driven by the same
4. for flash Like JFFS2 it is accessed directly from the on board flash but the contents of a CRAMFS filesystem cannot be modified This is a useful feature however if you need to be absolutely sure that your filesystem cannot be corrupted or altered Since CRAMFS is read only unlike ramdisks and JFFS2 you will need to combine it with either JFFS2 or a ramdisk to provide space for programs users to write files For example the ADS Debian CRAMFS distribution also uses a JFFS2 image for persistent storage You will have problems if you try to use a completely read only filesystem To program a kernel a CRAMFS filesystem and a JFFS2 filesystem into on board flash follow these steps ADS document 110010 40011 August 11 2005 Page 6 Applieddata net imbedded Computer Systems ADS U boot Bootloader Manual 1 Place a kernel zImage CRAMFS image cramfs img and JFFS2 image flashfs2 on your CF or MMC card 2 Place the U boot start txt on your card 3 Create a root_config txt on your card with the following contents images_to_flash zImage cramfs img flashfs2 setenv root_args rw root dev mtdblock3 noinitrd rootfstype cramfs setenv mtd_args mtdparts flash0 FLBLOCKSZ boot FLBLOCKSZ bootvars 2048k zImage 14848k cramfs img flashfs2 4 Insert your card into the board and apply power to boot your system 5 Important concepts in U boot 5 1 Using environment variables U boot stores its collection of se
5. in images_to_flash Note If your USB hard disk takes a longer time to become ready for Linux to use it it may be necessary to increase the rootdelay parameter to give your hard drive more time to settle before Linux mounts it Note In this example since the mtd_args have not been set in the root_config txt the default MTD partitioning will be used 3 3 Booting a full distribution from a Microdrive Microdrives are small rotating disk hard drives in a compact flash form factor Microdrives offer a large amount of storage up to 4GB at the time of writing at a reasonable cost and can be used to run a full ADS document 110010 40011 August 11 2005 Page 3 Applieddata net imbedded Computer Systema ADS U boot Bootloader Manual GNU Linux environment on your ADS board Since they employ a rotating disk hard drive instead of flash memory they are also suitable for repetitive use patterns such as software compilation and swap partitions virtual memory Since a Microdrive is seen by Linux as a PCMCIA device you must use an initial ramdisk or initrd to load the PCMCIA card manager cardmgr before mounting the root filesystem Such an initrd is provided with the Full Traditional Debian root filesystem for ADS boards Partition your Microdrive as follows 1 FAT12 or FAT16 bootloader partition U boot will read the kernel and other files from this partition About 10 MB will be needed 2 Linux swap Linux will us
6. most cases this command should copy the kernel into RAM and run it setenv boot linux cp zImage zImage_buffer bootm zImage_buffer If you have already copied a kernel into the zImage buffer e g from external media then boot_linux only needs to run the loaded kernel setenv boot linux bootm zImage buffer Note When a kernel and root filesystem are programmed to on board flash using the images to flash method the environment variables are automatically saved to on board flash as well 6 3 tty config txt Environment variables used in tty_config txt tty_args Part of the kernel command line where the console and serial ttys are configured setenv tty_args console ttyS0 38400 SERIALGETTY ttySO SERIALBAUD 38400 The console parameter determines where the Linux kernel messages will be sent The SERIALGETTY and SERIALBAUD parameters are variables used by the init process to configure the serial login terminals once Linux is running You can also specify a normal keyboard LCD tty as the console by setting console tty1 38400 Note Some hardware will require a different tty name ttyAMO ttyS1 to function properly ADS document 110010 40011 August 11 2005 Page 9 Applieddata net imbedded Computer Systema ADS U boot Bootloader Manual 6 4 hw_config txt The hw_config txt file is used to configure hardware registers prior to booting Linux This is most often used for setting up the framebuffer re
7. 40000 0x00040000 Flash bootargs Off zImage 0x00080000 0x00180000 Flash bootargs Off flashfs1 0x00200000 0x01e00000 Flash bootargs Off script_buffer 0xa0000800 0x00007800 DRAM Initial Off zImage_buffer 0xa0008000 0x00180000 DRAM Initial Off scratch_buffer 0xa0600000 0x01000000 DRAM Initial Off These regions are used by many of the ADS supplied scripts and default commands The regions of type Flash correspond to MTD partitions in on board flash and are named according to the partition names The regions of the DRAM are sections in memory and are used to hold scripts kernel images ramdisks and flash images that are loaded by U boot ADS document 110010 40011 August 11 2005 Page 14 Applieddata net imbedded Computer Systems ADS U boot Bootloader Manual The mapdel command deletes a named region from the map table The only argument is the name of the region to delete The mapadd command will add a named region in either DRAM or flash depending on the address to the map table The first argument is the name of the region The second argument is the beginning address of the region The third argument is the size of the region The fourth argument is optional and determines whether or not U boot will prevent writes to the region To create a new buffer called foo at address 0xa0600000 with a size of 16MiB 16777216 bytes enter the command mapadd foo 0xa0600000 0x01000000 Note U boot interprets most numerical
8. ADS U boot User s Manual ADS document 110010 40011 Applied Data Systems www applieddata net 10260 Old Columbia Road Columbia MD 21046 USA 301 490 4007 2005 ADS August 11 2005 Applieddata net imbedded Computer Systems ADS U boot Bootloader Manual ADS U boot Bootloader Manual 1 Overview This document is the bootloader user manual for ADS single board computers that run the U boot bootloader These boards use U boot to boot and run the Linux operating system If your ADS board does not run U boot please see the manual for your supported bootloader either the XScale PXA or SA1110 bootloader U boot is an open source multi platform bootloader with ports for many different embedded platforms U boot supports interactive commands environment variables command scripting and booting from external media PCMCIA CF MMC You can find more information about U boot and download its source code from U boot s Sourceforge home page at http u boot sourceforge net This is not an exhaustive manual for U boot If you are looking for a detailed reference manual or command index you should consult the main U boot manual at http www denx de twiki bin view DULG Manual To get started you will need a serial terminal program to view the output of U boot By default U boot sends it s output the the debug port on your board The manual for your board should indicate which serial port is the debug port W
9. ake changes 5 3 Scripts versus commands Being an interactive bootloader U boot has several built in commands that you can run from U boot s command prompt You can see a list of U boot commands by typing help at the command prompt More detailed information about built in U boot commands can be found in the official U boot manual Built in commands are run by simply typing the name of the command at the prompt In addition to the built in commands ADS U boot also supports scripts which are complex collections of commands stored in environment variables or text files on external media For more information on using scripts see chapter 9 of this manual 6 Boot and install scripts Boot scripts are files that are loaded by U boot from CF or MMC cards They contain U boot commands to set variables perform operations and execute other scripts to control U boot s behavior when it starts up Refer to the main U boot manual for information about U boot commands 6 1 start txt On boot ADS U boot looks for the file start txt 8 on external media CF or MMC if present on your board and if found loads and executes it Start txt instructs U boot to look for several other files which you can modify to control how your ADS board boots Linux root filesystems hardware registers etc Section 6 5 describes U boot s behavior without the start txt file Below is a list of the files start txt uses to boot your system In most circumstanc
10. e this partition as virtual memory A size of 64 to 128 MB is recommended 3 EXTS3 This is the root filesystem and should use the remaining space on the Microdrive Note ADS provides a Microdrive installer script with the full ADS Debian distribution tarball that will properly partition and format a Microdrive If you use this script you will only need to copy the U boot scripts onto the first partition Place the file initrd gz along with the zImage and the U boot scripts on the first FAT partition of your Microdrive Place the following in your root_config txt images_to_dram zImage initrd gz setenv root_args root dev hda3 initrd INITRD 3m ramdisk_size 6500 setenv boot linux bootm zImage buffer Note When using an EXT2 initrd with a 2 6 kernel do not include a rootfstype parameter as it will confuse the kernel if the initrd and the root filesystem types are different 3 4 Booting a full distribution from an NFS server If you have an NFS server available you can run the full Debian GNU Linux distribution by mounting your NFS server as the root filesystem This will give you all the benefits of running a full distribution without requiring a USB hard drive or Microdrive Place the following in your root_config txt images_to_dram zImage setenv root_args root dev nfs nfsroot NFS_server_IP path to root ip dhcp noinitrd setenv boot linux bootm zImage_buffer Note When setting up an
11. ernel from on board flash but flash does not contain a valid kernel If U boot is set up to boot from on board flash but on board flash does not contain a valid root filesystem Linux will give a kernel panic with an error message like this Unable to mount root on lt device gt Kernel panic not syncing VFS Unable to mount root fs on lt device gt You will need to re program your kernel and root filesystem or change the environment variables to point to a proper root filesystem in order to boot Linux properly 7 Register settings and hw config U boot uses the commands given in hw config txt to set up machine specific register settings prior to booting Linux This script replaces the functionality of the register txt files from our legacy PXA bootloader For each register setting a command is created that uses the U boot command mw to set a word at a particular address to a specific value Since the commands are stored in environment variables they can be STf your bootvars partition is erased the compiled in defaults will be used for the environment ADS document 110010 40011 August 11 2005 Page 10 Applieddata net imbedded Computer Systema ADS U boot Bootloader Manual given meaningful variable names The command hw_config is set to run all of the commands for configuring the hardware registers If there are too many individual mw commands 1 you will need to add subcommands as shown in the example below
12. es changes to these files should be all that is necessary to make your board boot the way you want it to You should not need to make any changes to start txt for typical operation 6 2 root_config txt The root_config txt file is used to tell U boot and Linux about the layout of your root filesystem The configuration in root_config txt is also used to build the Linux kernel command line SU boot presents an interactive command prompt if autoboot is interrupted during the 3 second timer at startup or if autoboot fails for any reason This is an ADS U boot extension See section 9 4 8 Actually it runs the bootcmd environment variable which by default executes the start environment variable ADS document 110010 40011 August 11 2005 Page 8 Applieddata net imbedded Computer Systems ADS U boot Bootloader Manual Environment variables used in root_config txt images to flash Space separated list of files to be programmed into on board flash The file names should correspond to MTD partition names in the mtd_args section images_to_flash zImage flashfs1 images_to_dram Space separated list of files to be loaded into RAM images_to_dram zImage ramdisk gz mtd_args Part of the kernel command line where MTD partitions are defined setenv mtd_args mtdparts flash0 FLBLOCKSZ boot FLBLOCKSZ bootvars 2048k zImage flashfs1 boot_linux This is the command U boot should run to finish booting linux In
13. ge 13 Applieddata net imbedded Computer Systema ADS U boot Bootloader Manual macaddr 00 60 0c aa bb cc The MAC address can be entered with or without the colons between the bytes No other type of separator is allowed Note You board should come from the factory pre programmed with a valid unique MAC address You should not change your board s MAC address unless you have a valid reason for doing so 9 4 Running scripts from text files The default U boot environment contains an ADS supplied script that allows you to easily run a U boot script that is stored as a text file on a CF or MMC card To run a U boot script from a text file specify the name of the script by typing txt_file my_script txt then run the script by typing run execute txt file You can also use this technique from within another text file script to call one script from another Note If files with the same name exist on both a CF and MMC card the CF card will take precedence Use printenv to observe the execute txt file variable 9 5 Map commands The commands mapinfo mapadd and mapdel can be used to maintain a human readable memory map This map allows you to name various memory ranges including flash regions partitions and memory regions buffers The output of the mapinfo command will list all of the default regions mapinfo Name Location Size Type Source Guard boot 0x00000000 0x00040000 Flash bootargs Off bootvars 0x000
14. gisters These settings will be specific to the type of board you are using See chapter 7 for more details Note The kernels for ADS Linux systems contain compiled in default hardware settings that will be used if hw_config txt is not present when booting These settings usually specify a 640x480 8 bit display for a LQ64D343 LCD display 6 5 U boot s behavior without external media If U boot does not find a CF or MMC card on boot or doesn t find the start txt file on any inserted CF or MMC cards U boot s behavior is controlled solely by the environment variables saved in the bootvars flash partition If you have programmed a kernel and root filesystem into on board flash using the procedures outlined in section 4 U boot s environment variables will be set to automatically boot that system after the three second delay If U boot is not interrupted by activity on the debug port Linux will boot automatically and you will not receive a U boot command prompt If you wish to alter the default behavior of U boot you should use the setenv command to change the environment variables Once you have set the environment variables the way you want them use the saveenv command to store your current environment into flash If U boot is not set up to boot from on board flash or if U boot s environment has been erased U boot will abort automatic booting and present its command prompt instead U boot will also abort if is set up to boot a k
15. indows usually comes with a serial terminal program called HyperTerminal many Linux distributions ship with either the minicom or the kermit serial terminal program installed ADS U boot uses a baud rate of 38400 8 data bits and no stop bits 2 Booting Linux on ADS boards with U boot This section presents some examples for booting various types of root filesystems on your ADS board U boot uses external media such as compact flash or MMC cards to load Linux images kernels ramdisks etc into either RAM or on board flash External media must be formatted with a FAT12 or FAT 16 filesystem to be used with U boot Compact flash cards can be used either in a compact flash slot or in a PCMCIA slot with a CF to PCMCIA adapter Note Most CF MMC cards come formatted with supported FAT filesystems so if you have a new card try it before you re format it The FAT requirement is only for U boot there are many formats that work fine once Linux is running 2 1 The ADS U boot boot scripts When booting from external media CF or MMC card you will need to place several U boot scripts on your card to control the behavior of U boot The scripts ADS provides split U boot s configuration into smaller sections making it easier to control how your board boots 1The DULG manual is targeted at a specific PowerPC board but the majority of the document also applies to other boards If your board is equipped with both a PCMCIA and a CF slot o
16. nly the PCMCIA slot slot 0 can be used with U boot ADS document 110010 40011 August 11 2005 Page 1 Applieddata net imbedded Computer Systema ADS U boot Bootloader Manual e start txt The main script which U boot loads and runs when booting from external media e root_config txt This file controls the type and location of the kernel and root filesystem Examples of root filesystems include ext2 ramdisks loaded from external media JFFS2 filesystems programmed into on board flash and ext3 filesystems stored on a Microdrive or USB hard drive This file also controls whether a kernel and root filesystem will be booted directly from external media or programmed into on board flash e hw config txt Configures machine specific hardware registers e g for framebuffer bit depth This file is optional and is only required if you need to change the default register settings e tty_config txt Configures the console serial TTYs and baud rate This file is optional and is only required if you need to change the default serial login or console settings If you wish to modify the booting behavior of U boot other than simply altering tty or root settings you should consider changing the value of the bootcmd environment variable or editing the start txt file to meet your needs Consult the main U boot manual for the commands and syntax used by U boot Under most situations the provided start txt file should meet your needs
17. o erase U boot s environment from within Linux to get a U boot prompt To prevent U boot from reading external media at startup you should change the start environment variable to boot your system only from on board flash The start variable stores the commands U boot runs during automatic boot To set a minimal automatic boot command type the following at the U boot command prompt setenv start test n hw config amp amp run hw_config test n boot_linux amp amp run boot_linux This start command would only read the hw_config and boot linux commands from the saved environment and not from external media These commands would also need to be stored in the environment Note You must run the saveenv command to save your environment changes to flash or they will be lost when you reboot 8 3 How to make U boot quiet Setting the environment variable silent to any value i e having this variable present will prevent U boot from sending any output to the debug port setenv silent 1 saveenv ADS document 110010 40011 August 11 2005 Page 12 Applieddata net imbedded Computer Systema ADS U boot Bootloader Manual When silent mode is enabled you can still get a U boot command prompt by pressing Enter during the autoboot countdown after applying power to the board The countdown will not be visible but the system still gives you a chance to interrupt the boot process To disable
18. silent mode clear the silent variable by typing setenv silent saveenv When the silent variable is set U boot will set the Linux console to null empty console on the command line automatically If you wish to silence the serial gettys as well you should disable comment out the serial login gettys in the file etc inittab 9 ADS specific features and changes 9 1 Raw zImage kernels Normally U boot expects to boot kernels from a special uzImage which encapsulates the Linux kernel into a U boot specific format The ADS U boot however also accepts raw zImage files as produced by a make zlmage command 9 2 Raw ASCII scripts ADS U boot provides the ability to run U boot scripts in memory without having to encapsulate the script inside a ulmage using the mkimage tool is not necessary This functionality allows the execute txt file script to load and execute scripts stored as ASCII text files on external media 9 3 Setting the ethernet MAC address On supported boards the U boot command macaddr can be used to set the ethernet MAC address The MAC address is a 6 byte hexadecimal number that uniquely identifies each endpoint on an ethernet network LAN You can view your board s MAC address by typing either macaddr with no arguments or printenv ethaddr To set the MAC address provide the address as an argument to the macaddr command as in the following example ADS document 110010 40011 August 11 2005 Pa
19. ssary to program a zImage and ramdisk gz to flash before booting it This type of root filesystem can be booted directly from a CF or MMC card 3 2 Booting a full distribution from a USB hard drive When running the full Debian GNU Linux distribution your ADS board becomes a complete native devel opment environment with compilers editors and debuggers You also have access to the Debian package system apt which provides thousands of pre compiled software packages ready to be installed on your ADS board Since U boot cannot actually boot load a kernel etc from a USB storage device you must prepare a CF or MMC card to boot from as well as a USB hard drive for the root filesystem Partition you USB hard drive as follows 1 Linux swap Linux will use this partition as virtual memory A size of 128 to 256 MB is recommended 2 Linux EXT3 This is the root filesystem You can use the remaining space on your USB hard drive for this partition but very large partition sizes will take a long time to check if a filesystem check is required Place the zImage and the U boot scripts on your external media and set the following environment variables in root_config txt images_to_dram zImage setenv root_args root dev sda2 rootfstype ext3 noinitrd rootdelay 5 setenv boot linux bootm zImage_buffer Since a USB hard drive requires no initial ramdisk initrd to be used as a root filesystem only the kernel zImage is listed
20. start txt file used to boot from external media Once your board s flash has been programmed with a kernel and root filesystem your board will boot that system whenever it is booted without external media Note After programming your flash you should immediately remove the external media and delete or rename the start txt file so you don t accidentally reprogram your system later on 4 2 Programming a kernel and ramdisk When your ADS board has a kernel and ramdisk programmed into on board flash U boot boots the system by loading the kernel zImage and the compressed ramdisk into system memory RAM and executing the Linux kernel Linux then uncompresses the ramdisk frees the memory consumed by the compressed copy and mounts the ramdisk as the root filesystem To program a kernel and ramdisk into on board flash follow these steps 1 Place a kernel zImage and ramdisk ramdisk gz on your CF or MMC card 2 Place the U boot start txt on your card 3 Create a root_config txt on your card with the following contents 5See section 4 ADS document 110010 40011 August 11 2005 Page 5 Applieddata net imbedded Computer Systema ADS U boot Bootloader Manual images_to_flash zImage ramdisk gz setenv root args root dev ram initrd INITRD 5m ramdisk_size 12288 rootfstype ext2 setenv mtd_args mtdparts flash0 FLBLOCKSZ boot FLBLOCKSZ bootvars 2048k zImage 5m ramdisk gz flashfs1 4 Insert your card in
21. to the board and apply power to boot your system Note The final partition flashfs1 is not programmed with any image in this example You can use this partition from within Linux however by erasing it and mounting it as jffs2 as in this example eraseall dev mtd4 mount t jffs2 dev mtdblock4 mnt flash The mount command or the first write to the filesystem may take a few minutes to complete as the filesystem is created checked 4 3 Programming a kernel and JFFS2 image JFFS2 is the second version of the journaling flash filesystem for Linux JFFS2 filesystems are accessed directly from the on board flash and do not consume large amounts of memory DRAM like ramdisks JFFS2 filesystems are writable and persistent allowing you to make permanent changes to the filesystem stored in your on board flash To program a kernel and JFFS2 filesystem into on board flash follow these steps 1 Place a kernel zImage and JFFS2 image flashfs1 on your CF or MMC card 2 Place the U boot start txt on your card 3 Create a root_config txt on your card with the following contents images_to_flash zImage flashfs1 setenv root_args root dev mtdblock3 noinitrd rootfstype jffs2 setenv mtd_args mtdparts flash0 FLBLOCKSZ boot FLBLOCKSZ bootvars 2048k zImage flashfs1 4 Insert your card into the board and apply power to boot your system 4 4 Programming a kernel and CRAMEFS image CRAMFS is a compressed read only filesystem
22. ttings commands and scripts in environment variables These environment variables are stored in the second flash partition named bootvars On boot U boot automatically attempts to load the environment variables from flash If U boot cannot load it s environment variables if the partition is corrupt or erased for instance you will see the following error message xxx Warning bad CRC using default environment and U boot will fall back to it s compiled in default environment To prevent this message from occurring again type saveenv to save the environment into flash 5 2 Restoring the default environment variables If you need to restore U boot s default environment you can remove all of the saved environment variables by typing run eraseenv at the U boot prompt and resetting your board When U boot restarts you will see the above error message and U boot will use it s compiled in defaults Again you should save these defaults to on board flash by typing saveenv ADS document 110010 40011 August 11 2005 Page 7 Applieddata net imbedded Computer Systems ADS U boot Bootloader Manual after restarting U boot Warning Restoring the default environment will destroy any changes made to the environment variables including configuration information needed to boot filesystems installed in on board flash You should capture the output of the printenv command to back up your environment if you m
23. values as hexadecimal values even if a leading 0x is not supplied A notable exception to this rule is the baudrate value which is interpreted as decimal 9 6 ADS supplied boot install scripts The files start txt hw_config txt root_config txt tty_config txt are boot scripts that ADS has provided to make it easier to control the behaviour of U boot These scripts break down the boot process into steps and allow for simpler individual files ADS document 110010 40011 August 11 2005 Page 15
24. verify that the file downloaded correctly 2 Insert the card into your board connect a serial terminal and boot your system 3 After applying power but before the three second timer expires press the Enter key to receive the U boot command prompt 4 If you are using a CF card either in a CF slot or a PCMCIA slot type the command run p_reprogram_uboot If you are using an MMC card type the command run mmc_reprogram_uboot 10U boot allows a maximum of 16 arguments per command ADS document 110010 40011 August 11 2005 Page 11 Applieddata net imbedded Computer Systema ADS U boot Bootloader Manual Warning Do not remove power from your board while U boot is being programmed Power loss during a bootloader update may render your board unbootable If this happens you may have to return the board to ADS for reprogramming 5 Once programming has completed you will see the following message Copy to Flash done You should now type reset to boot the newly installed U boot 8 2 How to make U boot secure To make U boot more secure there are several changes you can make to the environment variables to disable booting from external media and interactive booting To prevent U boot from allowing activity on the serial console from interrupting the automatic boot process remove the autoboot delay by running setenv bootdelay 0 Warning This will prevent you from getting a U boot prompt It will be necessary t
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