qmk_firmware/docs/QMK-Overview.md

# QMK Overview

This page attempts to explain the basic information you need to know to work with the QMK project. It assumes that you are familiar with navigating a UNIX shell, but does not assume you are familiar with C or with compiling using make.

# Basic QMK structure

QMK is a fork of @tmk's [tmk_keyboard](https://github.com/tmk/tmk_keyboard) project. The original TMK code, with modifications, can be found in the `tmk` folder. The QMK additions to the project may be found in the `quantum` folder. Keyboard projects may be found in the `handwired` and `keyboard` folders.

## Keyboard project structure

Within the `handwired` and `keyboard` folders is a directory for each keyboard project, for example `qmk_firmware/keyboards/clueboard`. Within you'll find the following structure:

* `keymaps/`: Different keymaps that can be built
* `rules.mk`: The file that sets the default "make" options. Do not edit this file directly, instead use a keymap specific `Makefile`.
* `config.h`: The file that sets the default compile time options. Do not edit this file directly, instead use a keymap specific `config.h`.

### Keymap structure

In every keymap folder, the following files may be found. Only `keymap.c` is required, if the rest of the files are not found the default options will be chosen.

* `config.h`: the options to configure your keymap
* `keymap.c`: all of your keymap code, required
* `Makefile`: the features of QMK that are enabled, required to run `make` in your keymap folder
* `readme.md`: a description of your keymap, how others might use it, and explanations of features
* Other files: Some people choose to include an image depicting the layout, and other files that help people to use or understand a particular keymap.

# The `make` command

The `make` command is how you compile the firmware into a .hex file, which can be loaded by a dfu programmer (like dfu-progammer via `make dfu`) or the [Teensy loader](https://www.pjrc.com/teensy/loader.html) (only used with Teensys). It it recommended that you always run make from within the `root` folder.

**NOTE:** To abort a make command press `Ctrl-c`

For more details on the QMK build process see [Make Instructions](/Make-Instructions.md).

### Simple instructions for building and uploading a keyboard

**Most keyboards have more specific instructions in the keyboard specific readme.md file, so please check that first**

1. Enter the `root` folder
2. Run `make <keyboard>-<subproject>-<keymap>-<programmer>`

In the above commands, replace:

* `<keyboard>` with the name of your keyboard
* `<keymap>` with the name of your keymap
* `<subproject>` with the name of the subproject (revision or sub-model of your keyboard). For example, for Ergodox it can be `ez` or `infinity`, and for Planck `rev3` or `rev4`.
  * If the keyboard doesn't have a subproject, or if you are happy with the default (defined in `rules.mk` file of the `keyboard` folder), you can leave it out. But remember to also remove the dash (`-`) from the command.
* `<programmer>` The programmer to use. Most keyboards use `dfu`, but some use `teensy`. Infinity keyboards use `dfu-util`. Check the readme file in the keyboard folder to find out which programmer to use.
  * If you  don't add `-<programmer` to the command line, the firmware will be still be compiled into a hex file, but the upload will be skipped.

**NOTE:** Some operating systems will refuse to program unless you run the make command as root for example `sudo make clueboard-default-dfu`

## Make Examples

* Build all Clueboard keymaps: `make clueboard`
* Build the default Planck keymap: `make planck-rev4-default`
* Build and flash your ergodox-ez: `make ergodox-ez-default-teensy`

# The `config.h` file

There are 2 `config.h` locations:

* keyboard (`/keyboards/<keyboard>/`)
* keymap (`/keyboards/<keyboard>/keymaps/<keymap>/`)

The keyboard `config.h` is included only if the keymap one doesn't exist. The format to use for your custom one [is here](https://github.com/qmk/qmk_firmware/blob/master/doc/keymap_config_h_example.h). If you want to override a setting from the parent `config.h` file, you need to do this:

```c
#undef MY_SETTING
#define MY_SETTING 4
```

For a value of `4` for this imaginary setting. So we `undef` it first, then `define` it.

You can then override any settings, rather than having to copy and paste the whole thing.