ECE597 icassp 2010 Lab 2 The Boot Sequence

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In the first lab you saw the BeagleBoard from a users point of view. In this lab we'll take a look at what's going on inside.

Connecting to the Beagle's serial port

If your Beagle is still running do this to shut it down.

  1. Start HyperTerminal
    • Go to Start:Accessories:Communications:HuperTermainal
  1. HyperTerminal init.png
  2. HyperTerminal Connect To.png
  3. HyperTerminal Properties.png

Shutting Down and Rebooting on U-Boot

yoder@beagleboard:~$ shutdown -r now

As your Beagle reboots you will see:

Texas Instruments X-Loader 1.4.2 (Feb 19 2009 - 12:01:24)
Reading boot sector
Loading u-boot.bin from mmc

Which is then followed by

U-Boot 2009.11-rc1 (Jan 08 2010 - 21:19:52)
 
OMAP3530-GP ES3.1, CPU-OPP2 L3-165MHz
OMAP3 Beagle board + LPDDR/NAND
I2C:   ready
DRAM:  256 MB
NAND:  256 MiB
In:    serial
Out:   serial
Err:   serial
Board revision C4
Die ID #5444000400000000040365fa1400e007
Hit any key to stop autoboot:  0
OMAP3 beagleboard.org #

Hit a key before it goes on to boot Linux. What has happened so far is:

  1. When power is first applied the Beagle jumps to a boot loader in the OMAPs ROM.
  2. This bootloader finds the SD card run runs a file called MLO.
  3. MLO is X-Loader with a couple things added. The first bit of output above is from X-Loader.
  4. X-Loader looks and finds u-boot.bin and starts running it.

Das U-Boot is universal boot loader that is used on many embedded systems. You can find more information at http://www.denx.de/wiki/U-Boot. You can list the commands it understands:

OMAP3 beagleboard.org # help
?       - alias for 'help'
base    - print or set address offset
bdinfo  - print Board Info structure
boot    - boot default, i.e., run 'bootcmd'
bootd   - boot default, i.e., run 'bootcmd'
bootm   - boot application image from memory
chpart  - change active partition
cmp     - memory compare
coninfo - print console devices and information
cp      - memory copy
crc32   - checksum calculation
echo    - echo args to console
editenv - edit environment variable
exit    - exit script
ext2load- load binary file from a Ext2 filesystem
ext2ls  - list files in a directory (default /)
false   - do nothing, unsuccessfully
fatinfo - print information about filesystem
fatload - load binary file from a dos filesystem
fatls   - list files in a directory (default /)
fsinfo  - print information about filesystems
fsload  - load binary file from a filesystem image
go      - start application at address 'addr'
help    - print command description/usage
i2c     - I2C sub-system
imxtract- extract a part of a multi-image
itest   - return true/false on integer compare
loadb   - load binary file over serial line (kermit mode)
loads   - load S-Record file over serial line
loady   - load binary file over serial line (ymodem mode)
loop    - infinite loop on address range
ls      - list files in a directory (default /)
md      - memory display
mm      - memory modify (auto-incrementing address)
mmc     - MMC sub-system
mtdparts- define flash/nand partitions
mtest   - simple RAM read/write test
mw      - memory write (fill)
nand    - NAND sub-system
nandecc - nandecc - switch OMAP3 NAND ECC calculation algorithm

nboot   - boot from NAND device
nm      - memory modify (constant address)
printenv- print environment variables
reset   - Perform RESET of the CPU
run     - run commands in an environment variable
saveenv - save environment variables to persistent storage
setenv  - set environment variables
showvar - print local hushshell variables
sleep   - delay execution for some time
source  - run script from memory
test    - minimal test like /bin/sh
true    - do nothing, successfully
version - print monitor version

U-Boot source code is available is highly configurable, therefore the command list can be expanded or reduced to fit your application. Try:

OMAP3 beagleboard.org # bdi
arch_number = 0x0000060A
env_t       = 0x00000000
boot_params = 0x80000100
DRAM bank   = 0x00000000
-> start    = 0x80000000
-> size     = 0x08000000
DRAM bank   = 0x00000001
-> start    = 0x88000000
-> size     = 0x08000000
baudrate    = 115200 bps

This gives you some information about the board. It appears we have some RAM starting at 0x8000 0000.

Booting Linux

Here's what happens when you boot Linux:

OMAP3 beagleboard.org # print bootcmd
bootcmd=mmc init;fatload mmc 0 80300000 uImage;bootm 80300000
OMAP3 beagleboard.org # print bootargs
bootargs=console=ttyS2,115200n8 console=tty0 root=/dev/mmcblk0p2 rw rootfstype=t