# Overview

The bootloader is a program that can update firmware images, initialize a device and possibly perform some sanity checks. The most important feature provided by the bootloader sample is the Firmware Over the Air (FOTA) functionality. Firmware can be loaded from a host microcontroller over UART or over the air from another wireless device using FOTA.

This document describes the bootloader firmware application and development tools. It shows you:

- How the bootloader firmware works
- How to create bootloader compatible applications and firmware images for RSL15
- How the bootloader protocol between the bootloader firmware and the UART updater PC tool works with the RSL15 EVB