By Aaron Bauch, Senior Field Application Engineer, IAR Systems Design specifications require the ability to update a device’s firmware in the field dynamically. This is done commonly via a bootloader. Designing a bootloader, however, is challenging as it must meet various requirements. For example, the mechanism for getting the new application into the MPU is…

The Boot-Loader is a code which executes when a microcontroller is powered ON or reset. It basically sets an environment for the application code to execute. It is the Boot-Loader that sets the hardware and loads the application code from any storage medium or received through external communication and let the application to execute. Thus a Boot-Loader has to perform the following basic function : Initialize the controller peripherals, Initialize the devices in the board, Allow an option for the user to select from the available applications to load, Load the selected application, Let the application code to execute. Apart from the above mentioned functions some Boot-Loaders can perform many other functions and there are Boot-Loaders which don’t perform all these functions like provide option to select the required application etc. The Boot-Loader codes in microcontrollers are actually very small and simple compared to the Boot-Loaders in advanced devices like PC. In most of the microcontroller the functionality of a Boot-Loader is limited only to set the initial clock and other settings for the microcontroller, load an application binary from the serial port etc. 

In the AVR microcontroller the flash memory is divided into two parts, namely Application Section and Boot Loader Section.  A code can be programmed into either the Application Section or the Boot loader Section (BLS). The code programmed into the Application section runs normally and is used for common applications, whereas the code running in the BLS is provided with some special features. The code running in the BLS section can execute Self Programing Mode (SPM) instructions which are blocked for the code running in the Application section. Using SPM instructions the code from the BLS can rewrite the code in the application section or the code in the BLS itself. The BLS section is normally used for storing the Boot-loader code for the microcontroller. The Boot-Loader code can be used for initializing the peripherals in the microcontroller, initialize the devices connected to the microcontroller, select the application to load and execute from a storage medium, load the selected application to the application section, jump to the application section and execute the application. 

  What is BootLoader? A Bootloader is the first program which executes (before the main program) whenever a system is initialized. In PC It is used to boot he OS of the system. In case of microcontrollers, a bootloader enriches the capabilities of the microcontroller and makes them self programmable device. This article will explore…