Certain high-level settings can be configured using a filed named ``card10.cfg``. It is accessed from the :ref:`usb_file_transfer` of the bootloader. Once you are in this mode and have mounted the badge's flash device, you can either create or update a file named ``card10.cfg``.
The file is in the well-known INI-style format, with one setting per line. For instance, if there were an option called ``answer_to_life``, you could set it by writing the following line in the ``card10.cfg`` file:
.. code-block:: text
answer_to_life = 42
Don't forget to unmount the filesystem before rebooting your badge after changing any setting.
Syntax and Types
----------------
Lines that start with a ``#`` character are ignored.
Any other line will have the overall syntax of ``option_name = option_value``, with spaces around the ``=`` character optional.
Option names are internal to card10 and described below. Each option has a defined type.
========= ===========
Type name Description
========= ===========
Boolean A true/false value. ``1`` or ``true`` is true, ``0`` or ``false`` is false. Example: ``foo = true``.
String An unquoted string value of maximum 20 bytes. Values longer than 20 bytes are trimmed. Example: ``foo = bar``.
Integer A signed 32-bit integer in base 10. Example: ``foo = 42`` or ``bar = -1337``.
Float A single-precision (32-bit) floating-point number in base 10. Example: ``foo = 13.37``.
========= ===========
Supported options
-----------------
=============== ========== ===========
Option name Type Description
=============== ========== ===========
``execute_elf`` Boolean Allow running of binary :ref:`l0dables`. These files can be nefarious, so this option is off by default.
Note: this feature is disabled by default and has to be enabled in :ref:`card10_cfg`. A :ref:`card10_cfg` file dropped into the :ref:`usb_file_transfer` of the badge containing ``execute_elf = true`` is enough.
l0dables are currently built within the source tree of the main repository. See ``l0dables/blinky`` for an example of a hello-world-like program. Within those programs, you can access the :ref:`epicardium_api` to control the hardware and behaviour of the badge.
.. todo::
Once you have a built ELF file, you can drop it into the FAT filesystem of the flash (eg. via :ref:`usb_file_transfer`) and it will be available from the menu program of the badge.
The card10 badge bootloader offers a USB Mass Storage mode to access its 8MB external flash.
This flash contains a FAT32 filesystem and files on it will be visible to software running on the badge.
Getting to the USB mode
-----------------------
To get to the USB mode, you will need to boot the badge while keeping the bottom-right button pressed.
.. image:: static/bootloader-buttons.png
1. If the badge is on, hold the top-left (power) button until the sleep screen appears, then release.
2. Start holding the bottom-right button.
3. Quickly press and release the top-left (power) button to turn the badge on.
4. Your badge should now be in file transfer mode, and you can then release the bottom-right button.
If you succesfully got into USB File Transfer mode, the screen will display its version and notify about the USB mode by displaying ``USB activated. Ready.``. If you connect the badge via USB to your computer, it should now detect 8MB of flash storage that you can mount in the same way as a pendrive.
This pendrive can contain multiple files with different functions, some of them outlined here:
============== ========
File name Function
============== ========
``card10.bin`` Firmware update file for the badge. If this file is present, the bootloader will perform an internal update to boot from this firmware file, then it will be deleted.
``main.py`` This file contains the default `application` to be run on power on.
``menu.py`` This file contains the default `menu` to be run when the power button is short-pressed.
``*.py`` These are application files written in (Micro)Python that can be run from the menu.
``*.elf`` These are :ref:`l0dables` that can be run from the menu.
============== ========
Updating files and rebooting
----------------------------
No matter which file you are writing, the bootloader will display a red ``Writing`` status message while write operations are pending. Please wait until it displays ``Ready`` again before resetting the badge by pressing the power button again.
