29 KiB
Quantum Mechanical Keyboard Firmware
You have found the QMK Firmware documentation site. This is a keyboard firmware based on the tmk_keyboard firmware with some useful features for Atmel AVR controllers, and more specifically, the OLKB product line, the ErgoDox EZ keyboard, and the Clueboard product line. It has also been ported to ARM chips using ChibiOS. You can use it to power your own hand-wired or custom keyboard PCB.
Getting started
Before you are able to compile, you'll need to install an environment for AVR development. You'll find the instructions for any OS below. If you find another/better way to set things up from scratch, please consider making a pull request with your changes!
Going beyond the keycodes
Aside from the basic keycodes, your keymap can include shortcuts to common operations.
Quick aliases to common actions
Your keymap can include shortcuts to common operations (called "function actions" in tmk). To learn more about them check out the Key Functions page.
Space Cadet Shift: The future, built in
Steve Losh described the Space Cadet Shift quite well. Essentially, you hit the left Shift on its own, and you get an opening parenthesis; hit the right Shift on its own, and you get the closing one. When hit with other keys, the Shift key keeps working as it always does. Yes, it's as cool as it sounds. Head on over to the Space Cadet Shift page to read about it.
The Leader key: A new kind of modifier
Most modifiers have to be held or toggled. But what if you had a key that indicated the start of a sequence? You could press that key and then rapidly press 1-3 more keys to trigger a macro, or enter a special layer, or anything else you might want to do. To learn more about it check out the Leader Key page.
Tap Dance: A single key can do 3, 5, or 100 different things
Hit the semicolon key once, send a semicolon. Hit it twice, rapidly -- send a colon. Hit it three times, and your keyboard's LEDs do a wild dance. That's just one example of what Tap Dance can do. Read more about it on the Tap Dance page.
Temporarily setting the default layer
DF(layer) - sets default layer to layer. The default layer is the one at the "bottom" of the layer stack - the ultimate fallback layer. This currently does not persist over power loss. When you plug the keyboard back in, layer 0 will always be the default. It is theoretically possible to work around that, but that's not what DF does.
Macro shortcuts: Send a whole string when pressing just one key
How would you like a single keypress to send a whole word, sentence, paragraph, or even document? Head on over to the Macros page to read up on all aspects of Simple and Dynamic Macros.
Additional keycode aliases for software-implemented layouts (Colemak, Dvorak, etc)
Everything is assuming you're in Qwerty (in software) by default, but there is built-in support for using a Colemak or Dvorak layout by including this at the top of your keymap:
#include <keymap_colemak.h>
If you use Dvorak, use keymap_dvorak.h instead of keymap_colemak.h for this line. After including this line, you will get access to:
CM_*for all of the Colemak-equivalent charactersDV_*for all of the Dvorak-equivalent characters
These implementations assume you're using Colemak or Dvorak on your OS, not on your keyboard - this is referred to as a software-implemented layout. If your computer is in Qwerty and your keymap is in Colemak or Dvorak, this is referred to as a firmware-implemented layout, and you won't need these features.
To give an example, if you're using software-implemented Colemak, and want to get an F, you would use CM_F - KC_F under these same circumstances would result in T.
Additional language support
In quantum/keymap_extras/, you'll see various language files - these work the same way as the alternative layout ones do. Most are defined by their two letter country/language code followed by an underscore and a 4-letter abbreviation of its name. FR_UGRV which will result in a ù when using a software-implemented AZERTY layout. It's currently difficult to send such characters in just the firmware (but it's being worked on - see Unicode support).
Unicode support
There are three Unicode keymap definition method available in QMK:
UNICODE_ENABLE
Supports Unicode input up to 0xFFFF. The keycode function is UC(n) in
keymap file, where n is a 4 digit hexadecimal.
UNICODEMAP_ENABLE
Supports Unicode up to 0xFFFFFFFF. You need to maintain a separate mapping
table const uint32_t PROGMEM unicode_map[] = {...} in your keymap file.
The keycode function is X(n) where n is the array index of the mapping
table.
UCIS_ENABLE
TBD
Unicode input in QMK works by inputing a sequence of characters to the OS, sort of like macro. Unfortunately, each OS has different ideas on how Unicode is inputted.
This is the current list of Unicode input method in QMK:
- UC_OSX: MacOS Unicode Hex Input support. Works only up to 0xFFFF. Disabled by default. To enable: go to System Preferences -> Keyboard -> Input Sources, and enable Unicode Hex.
- UC_LNX: Unicode input method under Linux. Works up to 0xFFFFF. Should work almost anywhere on ibus enabled distros. Without ibus, this works under GTK apps, but rarely anywhere else.
- UC_WIN: (not recommended) Windows built-in Unicode input. To enable: create registry key under
HKEY_CURRENT_USER\Control Panel\Input Method\EnableHexNumpadof typeREG_SZcalledEnableHexNumpad, set its value to 1, and reboot. This method is not recommended because of reliability and compatibility issue, use WinCompose method below instead. - UC_WINC: Windows Unicode input using WinCompose. Requires WinCompose. Works reliably under many (all?) variations of Windows.
Backlight Breathing
In order to enable backlight breathing, the following line must be added to your config.h file.
#define BACKLIGHT_BREATHING
The following function calls are used to control the breathing effect.
breathing_enable()- Enable the free-running breathing effect.breathing_disable()- Disable the free-running breathing effect immediately.breathing_self_disable()- Disable the free-running breathing effect after the current effect ends.breathing_toggle()- Toggle the free-running breathing effect.breathing_defaults()- Reset the speed and brightness settings of the breathing effect.
The following function calls are used to control the maximum brightness of the breathing effect.
breathing_intensity_set(value)- Set the brightness of the breathing effect when it is at its max value.breathing_intensity_default()- Reset the brightness of the breathing effect to the default value based on the current backlight intensity.
The following function calls are used to control the cycling speed of the breathing effect.
breathing_speed_set(value)- Set the speed of the breathing effect - how fast it cycles.breathing_speed_inc(value)- Increase the speed of the breathing effect by a fixed value.breathing_speed_dec(value)- Decrease the speed of the breathing effect by a fixed value.breathing_speed_default()- Reset the speed of the breathing effect to the default value.
The following example shows how to enable the backlight breathing effect when the FUNCTION layer macro button is pressed:
case MACRO_FUNCTION:
if (record->event.pressed)
{
breathing_speed_set(3);
breathing_enable();
layer_on(LAYER_FUNCTION);
}
else
{
breathing_speed_set(1);
breathing_self_disable();
layer_off(LAYER_FUNCTION);
}
break;
The following example shows how to pulse the backlight on-off-on when the RAISED layer macro button is pressed:
case MACRO_RAISED:
if (record->event.pressed)
{
layer_on(LAYER_RAISED);
breathing_speed_set(2);
breathing_pulse();
update_tri_layer(LAYER_LOWER, LAYER_RAISED, LAYER_ADJUST);
}
else
{
layer_off(LAYER_RAISED);
update_tri_layer(LAYER_LOWER, LAYER_RAISED, LAYER_ADJUST);
}
break;
Other firmware shortcut keycodes
RESET- puts the MCU in DFU mode for flashing new firmware (withmake dfu)DEBUG- the firmware into debug mode - you'll need hid_listen to see thingsBL_ON- turns the backlight onBL_OFF- turns the backlight offBL_<n>- sets the backlight to level nBL_INC- increments the backlight level by oneBL_DEC- decrements the backlight level by oneBL_TOGG- toggles the backlightBL_STEP- steps through the backlight levels
Enable the backlight from the Makefile.
Custom Quantum functions
All of these functions are available in the *_kb() or *_user() variety. kb ones should only be used in the <keyboard>/<keyboard>.c file, and user ones should only be used in the keymap.c. The keyboard ones call the user ones - it's necessary to keep these calls to allow the keymap functions to work correctly.
void matrix_init_*(void)
This function gets called when the matrix is initiated, and can contain start-up code for your keyboard/keymap.
void matrix_scan_*(void)
This function gets called at every matrix scan, which is basically as often as the MCU can handle. Be careful what you put here, as it will get run a lot.
bool process_record_*(uint16_t keycode, keyrecord_t *record)
This function gets called on every keypress/release, and is where you can define custom functionality. The return value is whether or not QMK should continue processing the keycode - returning false stops the execution.
The keycode variable is whatever is defined in your keymap, eg MO(1), KC_L, etc. and can be switch-cased to execute code whenever a particular code is pressed.
The record variable contains infomation about the actual press:
keyrecord_t record {
keyevent_t event {
keypos_t key {
uint8_t col
uint8_t row
}
bool pressed
uint16_t time
}
}
The conditional if (record->event.pressed) can tell if the key is being pressed or released, and you can execute code based on that.
void led_set_*(uint8_t usb_led)
This gets called whenever there is a state change on your host LEDs (eg caps lock, scroll lock, etc). The LEDs are defined as:
#define USB_LED_NUM_LOCK 0
#define USB_LED_CAPS_LOCK 1
#define USB_LED_SCROLL_LOCK 2
#define USB_LED_COMPOSE 3
#define USB_LED_KANA 4
and can be tested against the usb_led with a conditional like if (usb_led & (1<<USB_LED_CAPS_LOCK)) - if this is true, you can turn your LED on, otherwise turn it off.
Modding your keyboard
Audio output from a speaker
Your keyboard can make sounds! If you've got a Planck, Preonic, or basically any keyboard that allows access to the C6 port, you can hook up a simple speaker and make it beep. You can use those beeps to indicate layer transitions, modifiers, special keys, or just to play some funky 8bit tunes.
The audio code lives in quantum/audio/audio.h and in the other files in the audio directory. It's enabled by default on the Planck stock keymap. Here are the important bits:
#include "audio.h"
Then, lower down the file:
float tone_startup[][2] = {
ED_NOTE(_E7 ),
E__NOTE(_CS7),
E__NOTE(_E6 ),
E__NOTE(_A6 ),
M__NOTE(_CS7, 20)
};
This is how you write a song. Each of these lines is a note, so we have a little ditty composed of five notes here.
Then, we have this chunk:
float tone_qwerty[][2] = SONG(QWERTY_SOUND);
float tone_dvorak[][2] = SONG(DVORAK_SOUND);
float tone_colemak[][2] = SONG(COLEMAK_SOUND);
float tone_plover[][2] = SONG(PLOVER_SOUND);
float tone_plover_gb[][2] = SONG(PLOVER_GOODBYE_SOUND);
float music_scale[][2] = SONG(MUSIC_SCALE_SOUND);
float goodbye[][2] = SONG(GOODBYE_SOUND);
Wherein we bind predefined songs (from quantum/audio/song_list.h) into named variables. This is one optimization that helps save on memory: These songs only take up memory when you reference them in your keymap, because they're essentially all preprocessor directives.
So now you have something called tone_plover for example. How do you make it play the Plover tune, then? If you look further down the keymap, you'll see this:
PLAY_NOTE_ARRAY(tone_plover, false, 0); // Signature is: Song name, repeat, rest style
This is inside one of the macros. So when that macro executes, your keyboard plays that particular chime.
"Rest style" in the method signature above (the last parameter) specifies if there's a rest (a moment of silence) between the notes.
Recording And Playing back Music
Music On- Turn music mode on. The default mapping isLower+Upper+CLCTL- start a recording- play some tones
LALT- stop recording, stop playingLGUI- play recordingLALT- stop playingMusic Off- Turn music mode off. The default mapping isLower+Upper+V
MIDI functionalty
This is still a WIP, but check out quantum/keymap_midi.c to see what's happening. Enable from the Makefile.
Bluetooth functionality
This requires some hardware changes, but can be enabled via the Makefile. The firmware will still output characters via USB, so be aware of this when charging via a computer. It would make sense to have a switch on the Bluefruit to turn it off at will.
International Characters on Windows
AutoHotkey allows Windows users to create custom hotkeys among others.
The method does not require Unicode support in the keyboard itself but depends instead of AutoHotkey running in the background.
First you need to select a modifier combination that is not in use by any of your programs.
CtrlAltWin is not used very widely and should therefore be perfect for this.
There is a macro defined for a mod-tab combo LCAG_T.
Add this mod-tab combo to a key on your keyboard, e.g.: LCAG_T(KC_TAB).
This makes the key behave like a tab key if pressed and released immediately but changes it to the modifier if used with another key.
In the default script of AutoHotkey you can define custom hotkeys.
<^<!<#a::Send, ä
<^<!<#<+a::Send, Ä
The hotkeys above are for the combination CtrlAltGui and CtrlAltGuiShift plus the letter a.
AutoHotkey inserts the Text right of Send, when this combination is pressed.
RGB Under Glow Mod
Here is a quick demo on Youtube (with NPKC KC60) (https://www.youtube.com/watch?v=VKrpPAHlisY).
For this mod, you need an unused pin wiring to DI of WS2812 strip. After wiring the VCC, GND, and DI, you can enable the underglow in your Makefile.
RGBLIGHT_ENABLE = yes
In order to use the underglow animation functions, you need to have #define RGBLIGHT_ANIMATIONS in your config.h.
Please add the following options into your config.h, and set them up according your hardware configuration. These settings are for the F4 pin by default:
#define RGB_DI_PIN F4 // The pin your RGB strip is wired to
#define RGBLIGHT_ANIMATIONS // Require for fancier stuff (not compatible with audio)
#define RGBLED_NUM 14 // Number of LEDs
#define RGBLIGHT_HUE_STEP 10
#define RGBLIGHT_SAT_STEP 17
#define RGBLIGHT_VAL_STEP 17
You'll need to edit RGB_DI_PIN to the pin you have your DI on your RGB strip wired to.
The firmware supports 5 different light effects, and the color (hue, saturation, brightness) can be customized in most effects. To control the underglow, you need to modify your keymap file to assign those functions to some keys/key combinations. For details, please check this keymap. keyboards/planck/keymaps/yang/keymap.c
WS2812 Wiring
Please note the USB port can only supply a limited amount of power to the keyboard (500mA by standard, however, modern computer and most usb hubs can provide 700+mA.). According to the data of NeoPixel from Adafruit, 30 WS2812 LEDs require a 5V 1A power supply, LEDs used in this mod should not more than 20.
PS/2 Mouse Support
Its possible to hook up a PS/2 mouse (for example touchpads or trackpoints) to your keyboard as a composite device.
There are three available modes for hooking up PS/2 devices: USART (best), interrupts (better) or busywait (not recommended).
Busywait version
Note: This is not recommended, you may encounter jerky movement or unsent inputs. Please use interrupt or USART version if possible.
In rules.mk:
PS2_MOUSE_ENABLE = yes
PS2_USE_BUSYWAIT = yes
In your keyboard config.h:
#ifdef PS2_USE_BUSYWAIT
# define PS2_CLOCK_PORT PORTD
# define PS2_CLOCK_PIN PIND
# define PS2_CLOCK_DDR DDRD
# define PS2_CLOCK_BIT 1
# define PS2_DATA_PORT PORTD
# define PS2_DATA_PIN PIND
# define PS2_DATA_DDR DDRD
# define PS2_DATA_BIT 2
#endif
Interrupt version
The following example uses D2 for clock and D5 for data. You can use any INT or PCINT pin for clock, and any pin for data.
In rules.mk:
PS2_MOUSE_ENABLE = yes
PS2_USE_INT = yes
In your keyboard config.h:
#ifdef PS2_USE_INT
#define PS2_CLOCK_PORT PORTD
#define PS2_CLOCK_PIN PIND
#define PS2_CLOCK_DDR DDRD
#define PS2_CLOCK_BIT 2
#define PS2_DATA_PORT PORTD
#define PS2_DATA_PIN PIND
#define PS2_DATA_DDR DDRD
#define PS2_DATA_BIT 5
#define PS2_INT_INIT() do { \
EICRA |= ((1<<ISC21) | \
(0<<ISC20)); \
} while (0)
#define PS2_INT_ON() do { \
EIMSK |= (1<<INT2); \
} while (0)
#define PS2_INT_OFF() do { \
EIMSK &= ~(1<<INT2); \
} while (0)
#define PS2_INT_VECT INT2_vect
#endif
USART version
To use USART on the ATMega32u4, you have to use PD5 for clock and PD2 for data. If one of those are unavailable, you need to use interrupt version.
In rules.mk:
PS2_MOUSE_ENABLE = yes
PS2_USE_USART = yes
In your keyboard config.h:
#ifdef PS2_USE_USART
#define PS2_CLOCK_PORT PORTD
#define PS2_CLOCK_PIN PIND
#define PS2_CLOCK_DDR DDRD
#define PS2_CLOCK_BIT 5
#define PS2_DATA_PORT PORTD
#define PS2_DATA_PIN PIND
#define PS2_DATA_DDR DDRD
#define PS2_DATA_BIT 2
/* synchronous, odd parity, 1-bit stop, 8-bit data, sample at falling edge */
/* set DDR of CLOCK as input to be slave */
#define PS2_USART_INIT() do { \
PS2_CLOCK_DDR &= ~(1<<PS2_CLOCK_BIT); \
PS2_DATA_DDR &= ~(1<<PS2_DATA_BIT); \
UCSR1C = ((1 << UMSEL10) | \
(3 << UPM10) | \
(0 << USBS1) | \
(3 << UCSZ10) | \
(0 << UCPOL1)); \
UCSR1A = 0; \
UBRR1H = 0; \
UBRR1L = 0; \
} while (0)
#define PS2_USART_RX_INT_ON() do { \
UCSR1B = ((1 << RXCIE1) | \
(1 << RXEN1)); \
} while (0)
#define PS2_USART_RX_POLL_ON() do { \
UCSR1B = (1 << RXEN1); \
} while (0)
#define PS2_USART_OFF() do { \
UCSR1C = 0; \
UCSR1B &= ~((1 << RXEN1) | \
(1 << TXEN1)); \
} while (0)
#define PS2_USART_RX_READY (UCSR1A & (1<<RXC1))
#define PS2_USART_RX_DATA UDR1
#define PS2_USART_ERROR (UCSR1A & ((1<<FE1) | (1<<DOR1) | (1<<UPE1)))
#define PS2_USART_RX_VECT USART1_RX_vect
#endif
#endif
#endif
Additional Settings
PS/2 mouse features
These enable settings supported by the PS/2 mouse protocol: http://www.computer-engineering.org/ps2mouse/
/* Use remote mode instead of the default stream mode (see link) */
#define PS2_MOUSE_USE_REMOTE_MODE
/* Enable the scrollwheel or scroll gesture on your mouse or touchpad */
#define PS2_MOUSE_ENABLE_SCROLLING
/* Some mice will need a scroll mask to be configured. The default is 0xFF. */
#define PS2_MOUSE_SCROLL_MASK 0x0F
/* Applies a transformation to the movement before sending to the host (see link) */
#define PS2_MOUSE_USE_2_1_SCALING
/* The time to wait after initializing the ps2 host */
#define PS2_MOUSE_INIT_DELAY 1000 /* Default */
You can also call the following functions from ps2_mouse.h
void ps2_mouse_disable_data_reporting(void);
void ps2_mouse_enable_data_reporting(void);
void ps2_mouse_set_remote_mode(void);
void ps2_mouse_set_stream_mode(void);
void ps2_mouse_set_scaling_2_1(void);
void ps2_mouse_set_scaling_1_1(void);
void ps2_mouse_set_resolution(ps2_mouse_resolution_t resolution);
void ps2_mouse_set_sample_rate(ps2_mouse_sample_rate_t sample_rate);
Fine control
Use the following defines to change the sensitivity and speed of the mouse.
Note: you can also use ps2_mouse_set_resolution for the same effect (not supported on most touchpads).
#define PS2_MOUSE_X_MULTIPLIER 3
#define PS2_MOUSE_Y_MULTIPLIER 3
#define PS2_MOUSE_V_MULTIPLIER 1
Scroll button
If you're using a trackpoint, you will likely want to be able to use it for scrolling. Its possible to enable a "scroll button/s" that when pressed will cause the mouse to scroll instead of moving. To enable the feature, you must set a scroll button mask as follows:
#define PS2_MOUSE_SCROLL_BTN_MASK (1<<PS2_MOUSE_BUTTON_MIDDLE) /* Default */
To disable the scroll button feature:
#define PS2_MOUSE_SCROLL_BTN_MASK 0
The available buttons are:
#define PS2_MOUSE_BTN_LEFT 0
#define PS2_MOUSE_BTN_RIGHT 1
#define PS2_MOUSE_BTN_MIDDLE 2
You can also combine buttons in the mask by |ing them together.
Once you've configured your scroll button mask, you must configure the scroll button send interval. This is the interval before which if the scroll buttons were released they would be sent to the host. After this interval, they will cause the mouse to scroll and will not be sent.
#define PS2_MOUSE_SCROLL_BTN_SEND 300 /* Default */
To disable sending the scroll buttons:
#define PS2_MOUSE_SCROLL_BTN_SEND 0
Fine control over the scrolling is supported with the following defines:
#define PS2_MOUSE_SCROLL_DIVISOR_H 2
#define PS2_MOUSE_SCROLL_DIVISOR_V 2
Debug settings
To debug the mouse, add debug_mouse = true or enable via bootmagic.
/* To debug the mouse reports */
#define PS2_MOUSE_DEBUG_HID
#define PS2_MOUSE_DEBUG_RAW
Safety Considerations
You probably don't want to "brick" your keyboard, making it impossible to rewrite firmware onto it. Here are some of the parameters to show what things are (and likely aren't) too risky.
- If your keyboard map does not include RESET, then, to get into DFU mode, you will need to press the reset button on the PCB, which requires unscrewing the bottom.
- Messing with tmk_core / common files might make the keyboard inoperable
- Too large a .hex file is trouble;
make dfuwill erase the block, test the size (oops, wrong order!), which errors out, failing to flash the keyboard, leaving it in DFU mode.- To this end, note that the maximum .hex file size on Planck is 7000h (28672 decimal)
Linking: .build/planck_rev4_cbbrowne.elf [OK]
Creating load file for Flash: .build/planck_rev4_cbbrowne.hex [OK]
Size after:
text data bss dec hex filename
0 22396 0 22396 577c planck_rev4_cbbrowne.hex
- The above file is of size 22396/577ch, which is less than 28672/7000h
- As long as you have a suitable alternative .hex file around, you can retry, loading that one
- Some of the options you might specify in your keyboard's Makefile consume extra memory; watch out for BOOTMAGIC_ENABLE, MOUSEKEY_ENABLE, EXTRAKEY_ENABLE, CONSOLE_ENABLE, API_SYSEX_ENABLE
- DFU tools do /not/ allow you to write into the bootloader (unless you throw in extra fruitsalad of options), so there is little risk there.
- EEPROM has around a 100000 write cycle. You shouldn't rewrite the firmware repeatedly and continually; that'll burn the EEPROM eventually.
Porting your keyboard to QMK
If your keyboard is running an Atmega chip (atmega32u4 and others), it's pretty easy to get things setup for compiling your own firmware to flash onto your board. There is a /util/new_project.sh <keyboard> script to help get you started - you can simply pass your keyboard's name into the script, and all of the necessary files will be created. The components of each are described below.
/keyboards/<keyboard>/config.h
The USB Device descriptor parameter block contains parameters are used to uniquely identify your keyboard, but they don't really matter to the machine.
Your MATRIX_ROWS and MATRIX_COLS are the numbers of rows and cols in your keyboard matrix - this may be different than the number of actual rows and columns on your keyboard. There are some tricks you can pull to increase the number of keys in a given matrix, but most keyboards are pretty straight-forward.
The MATRIX_ROW_PINS and MATRIX_COL_PINS are the pins your MCU uses on each row/column. Your schematic (if you have one) will have this information on it, and the values will vary depending on your setup. This is one of the most important things to double-check in getting your keyboard setup correctly.
For the DIODE_DIRECTION, most hand-wiring guides will instruct you to wire the diodes in the COL2ROW position, but it's possible that they are in the other - people coming from EasyAVR often use ROW2COL. Nothing will function if this is incorrect.
BACKLIGHT_PIN is the pin that your PWM-controlled backlight (if one exists) is hooked-up to. Currently only B5, B6, and B7 are supported.
BACKLIGHT_BREATHING is a fancier backlight feature that adds breathing/pulsing/fading effects to the backlight. It uses the same timer as the normal backlight. These breathing effects must be called by code in your keymap.
BACKLIGHT_LEVELS is how many levels exist for your backlight - max is 15, and they are computed automatically from this number.
/keyboards/<keyboard>/Makefile
The values at the top likely won't need to be changed, since most boards use the atmega32u4 chip. The BOOTLOADER_SIZE will need to be adjusted based on your MCU type. It's defaulted to the Teensy, since that's the most common controller. Below is quoted from the Makefile.
# Boot Section Size in *bytes*
# Teensy halfKay 512
# Teensy++ halfKay 1024
# Atmel DFU loader 4096
# LUFA bootloader 4096
# USBaspLoader 2048
OPT_DEFS += -DBOOTLOADER_SIZE=512
At the bottom of the file, you'll find lots of features to turn on and off - all of these options should be set with ?= to allow for the keymap overrides. ?= only assigns if the variable was previously undefined. For the full documenation of these features, see the Makefile options.
/keyboards/<keyboard>/readme.md
This is where you'll describe your keyboard - please write as much as you can about it! Talking about default functionality/features is useful here. Feel free to link to external pages/sites if necessary. Images can be included here as well. This file will be rendered into a webpage at qmk.fm/keyboards//.
/keyboards/<keyboard>/<keyboard>.c
This is where all of the custom logic for your keyboard goes - you may not need to put anything in this file, since a lot of things are configured automatically. All of the *_kb() functions are defined here. If you modify them, remember to keep the calls to *_user(), or things in the keymaps might not work. You can read more about the functions here
/keyboards/<keyboard>/<keyboard>.h
Here is where you can (optionally) define your KEYMAP function to remap your matrix into a more readable format. With ortholinear boards, this isn't always necessary, but it can help to accomodate the dead spots on your matrix, where there are keys that take up more than one space (2u, staggering, 6.25u, etc). The example shows the difference between the physical keys, and the matrix design:
#define KEYMAP( \
k00, k01, k02, \
k10, k11 \
) \
{ \
{ k00, k01, k02 }, \
{ k10, KC_NO, k11 }, \
}
Each of the kxx variables needs to be unique, and usually follows the format k<row><col>. You can place KC_NO where your dead keys are in your matrix.