The document discusses board bringup and the startup process. It explains that on power on, the processor executes initial startup code which loads a stage 1 bootloader. The stage 1 bootloader then loads a stage 2 bootloader which loads the operating system. The operating system then starts the init application, which starts other applications and daemons. It also discusses understanding the target board hardware, restoring it to a factory default state, and using vendor-provided utilities.

1. Board Bringup
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2. What to Expect?
Board specific Details
Understanding the target board
How to play with the target board?
Peeking into Vendor supplied Utilities, if
any
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3. Startup Doubts
Typical doubts you may have, be it your
desktop or board
What happens when you switch on the power?
Where does the processor starts executing on
“Power on Reset”?
What code is there? Do you have access to that
code?
How does the Operating System boot up?
How does the login prompt come?
Any many more
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4. Startup Sequence
To Decode all these, let's understand the
Startup Sequence
Processor / Controller Startup
Bootloader or the Software Startup
Operating System Startup
Application Startup
Though they may vary from board to board,
we can have a generic overview
And then, we shall get into your board
specifics
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5. Processor / Controller Startup
Controller Internal Code
Mostly exists in Controllers (Embedded Systems)
System Startup / Setup Code
Mostly exists for Processors in Desktops
Processors jump to a pre-designated address, typically Zero,
to run these pre-programmed code
Referred as BIOS in the Desktop parlance
Needs to be programmed once, on virgin boards
In both the cases, the Code looks for the Stage1
Bootloader at the designated places
Embedded: EEPROM, Flash, Serial Download, …
Desktops: Floppy, CDROM, Hard Disk, Network, ...
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6. Software Startup
Stage 1 Bootloader
Initial Program Loader (IPL) in Embedded World
Master Boot Record (MBR) in Desktops
Constrained to limited Space. Can't do much
So, loads
Stage 2 Bootloader
Have enough space to do luxurious stuff
Provides configurability and management features
Loads the Operating System
Passes arguments to the Operating System
Jumps to start executing the Operating System
For Desktops: LILO, GRUB, SYSLINUX, ...
In Embedded Systems: u-boot and others
Also called Secondary Program Loader (SPL)
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7. Operating System Startup
Uncompresses the kernel, if compressed
Configures itself based on the arguments
from the Stage 2 Bootloader
Setup the Kernel Space
Jump execution to the first application
“init”
Common to both Desktop & Embedded
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8. Application Startup
init
This could be the application binary itself. Or,
Could be a link to it
It typically starts the various daemons
And then does things as per the system's
requirement
In Desktop, starts the login process to provide login
prompts
In Embedded Systems, does the same at least
during Development Cycle
Later, may do specific to customer requirement
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9. Startup Sequence
Power Up / Reset BIOS
System Startup Controller Code
Master Boot Record
Stage 1 Bootloader Initial Program Loader
LILO, GRUB, …
Stage 2 Bootloader u-boot, ...
Operating System Linux Kernel
Operational Application init → busbox, ...
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10. Let's Startup the Board
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11. Anatomy of Development Board
Being a Embedded Developer, you should
know your board in more detail
Both
Hardware
Major components
Types of memories
Software
Manufactured State
Factory Restoration
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12. Let's Browse the Board
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13. Manufactured State
State at which, it was when manufactured
Also called the Virgin State
Achieved by erasing all the memories
EEPROM
Flash – NOR, NAND, ...
This, in principle erases
Bootloaders – Stage 1 & Stage 2
Kernel
File Systems
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14. Factory Restoration
So, this is to get the Board back to boot up
In principle, populating back the memories erased with
Stage 1 & Stage 2 Bootloaders
Kernel
Root File System
Optionally, the Other File Systems
Would need some special utilities
Provided by the board vendor (the factory guy)
Examples: RAM Monitor, Boot Monitor, ...
At times of nothing, these are good debug utilities, as well
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15. What all have we done?
Understood the target board
Switching it on
Accessing the stuff on it
Configuring it
How to play with the target board?
Decoding the Hardware
Taking it to a virgin state
Restoring it to factory defaults
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16. Any Queries?
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