What is "Boot Loader" ??

[yasser_shoukry]

Hi all,
I want to know what is meant by a "Boot Loader" file ? What does it contain and what applications do i need one ??

thanks in advance.

 

[SkyHigh]

A bootloader is a special program that is used to provide self-programming or reload or update your application program in a microcontroller that supports bootloader.

For example, ATMega128L is an Atmel microcontroller.
It has a flash that can be divided into 2 sections, namely the RWW (Read-While-Write) and NRWW (Non-Read-While-Write Memory) Sections.

Your normal application program is stored in RWW section.
Your bootloader program is stored in the NRWW section.

For example, if you have a PC GUI software to control this MCU, instead of using the in-serial programmer or debugger, you can use a normal serial UART to update your application program using the bootloader program.

In other words, the microcontroller enters the bootloader program. It executes the instructions in the bootloader. The microcontroller will erase your application program. Then it will read all the bytes from the serial UART and stores the new bytes in the RWW section where your new application program is residing. In this way, newly updated application program is now residing in your flash memory.

Sometimes, this is also called self-programming.

(1) For the very first time, bootloader must be flashed by the in-circuit/serial/system programmer/debugger into the microcontroller.
(2) To achieve this, the programmer software must set the fuses of the microcontroller to activate bootloader options.

From this onwards, your in-serial programmer becomes an optional tool.

Update of new application program can be done through other GPIOs or even UART. This is possible by specifying port pins in your bootloader program to read in bytes that will form your application program.