The micro:bit firmware
Firmware is like software in that it is changeable. It's somewhere between software and hardware - it is stored inside flash memory inside the device, and can be user updated if needed.
The Firmware on the micro:bit is stored inside a separate interface chip called the KL26, which is the small chip on the top right of the circuit board at the back. It is the responsibility of this firmware to connect to the USB port, and allow you to drag and drop .hex files that then get programmed into the application processor (a separate chip on the micro:bit called the nRF51, the bigger chip on the top left of the circuit board).
If you want to find out what firmware is loaded into the KL26 interface chip, plug it in and open it in your file manager, and look inside the details.txt file
You might want to upgrade your firmware to get access to new features - for example, the Big Crunch food survey project introduced some new features which required a firmware update.
Updating the firmware
The latest released firmware for the interface chip is attached to this article. Download the .hex file to your computer. Then with the battery pack removed and the USB connected, hold the reset button at the back of the micro:bit and plug the USB lead into your computer.
You should see a drive appear in your file manager called MAINTENANCE. Drag and drop the .hex file from this article onto the MAINTENANCE drive and wait for the yellow system LED at the back to stop flashing. When the upgrade is completed, the micro:bit will reset and the drive will disappear from your computer, and the MICROBIT drive re-appear.
Finally, check the details.txt file that is on the MICROBIT drive and make sure that it has the same version number as the .hex firmware that you just flashed to the interface chip.
This firmware package came from the official DAPLink github repository
Kewords for search: upgrade the built-in firmware, software, hardware, maintenance