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@@ -45,19 +45,19 @@ Before you are able to compile, you'll need to install an environment for AVR de
 
 ### Windows 10
 
-It's still recommended to use the method for Vista and later below. The reason for this is that the Windows 10 Subsystem for Linux lacks [USB support](https://wpdev.uservoice.com/forums/266908-command-prompt-console-bash-on-ubuntu-on-windo/suggestions/13355724-unable-to-access-usb-devices-from-bash), so it's not possible to flash the firmware to the keyboard. Please add your vote to the link!
+Due to some issues with the "Windows (Vista and later)" instructions below, we now recommend following these instructions if you use Windows, which will allow you to use the Windows Subsystem for Linux to compile the firmware. If you are not using Windows 10 with the Anniversary Update installed (which came out in July 2016), you will need to use one of the other methods, such as Docker, Vagrant, or the instructions for Vista and later. 
 
-That said, it's still possible to use it for compilation. And recommended, if you need to compile much, since it's much faster than at least Cygwin (which is also supported, but currently lacking documentation). I haven't tried the method below, so I'm unable to tell.
+If you use this method, you will need to use a standalone tool to flash the firmware to the keyboard after you compile it. We recommend the official [QMK Firmware Flasher](https://github.com/jackhumbert/qmk_firmware_flasher/releases). This is because the Windows 10 Subsystem for Linux lacks [libUSB support](https://wpdev.uservoice.com/forums/266908-command-prompt-console-bash-on-ubuntu-on-windo/suggestions/13355724-unable-to-access-usb-devices-from-bash), so it can't access the keyboard's microcontroller. Please add your vote for Microsoft to fix this issue using the link!
 
 Here are the steps
 
 1. Install the Windows 10 subsystem for Linux, following [these instructions](http://www.howtogeek.com/249966/how-to-install-and-use-the-linux-bash-shell-on-windows-10/).
-2. If you have previously cloned the repository using the normal Git bash, you will need to clean up the line endings. If you have cloned it after 20th of August 2016, you are likely fine. To clean up the line endings do the following
+2. If you have  cloned the repository using git before August 20, 2016, clean up the line endings from wherever you currently access git:
-   1. Make sure that you have no changes you haven't committed by running `git status`, if you do commit them first
+   1. Make sure that you have no changes you haven't committed by running `git status`. ANY UNCOMMITTED CHANGES WILL BE PERMANENTLY LOST.
-   2. From within the Git bash run `git rm --cached -r .`
+   2. Run `git rm --cached -r .`
-   3. Followed by `git reset --hard`
+   3. Run `git reset --hard`
-3. Start the "Bash On Ubuntu On Windows" from the start menu
+3. Open "Bash On Ubuntu On Windows" from the start menu
-4. With the bash open, navigate to your Git checkout. The harddisk can be accessed from `/mnt` for example `/mnt/c` for the `c:\` drive.
+4. With the bash window open, navigate to your copy of the [qmk_firmware repository](https://github.com/jackhumbert/qmk_firmware) using the `cd` command. The harddisks can be accessed from `/mnt/<driveletter>`. For example, your main hard drive (C:) can be accessed by executiing the command `cd /mnt/c`. If your username is John and the qmk_firmware folder is in your Downloads folder, you can move to it with the command `cd /mnt/c/Users/John/Downloads/qmk_firmware`. You can use the Tab key as you go to help you autocomplete the folder names.
 5. Run `sudo util/install_dependencies.sh`.
 6. After a while the installation will finish, and you are good to go
 
@@ -140,6 +140,9 @@ If this is a bit complex for you, Docker might be the turn-key solution you need
 
 docker run -e keymap=gwen -e keyboard=ergodox --rm -v $('pwd'):/qmk:rw edasque/qmk_firmware
 
+# On windows docker seems to have issue with VOLUME tag in Dockerfile, and $('pwd') won't print a windows compliant path, use full path instead like this
+docker run -e keymap=default -e keyboard=ergobop --rm -v D:/Users/Sacapuces/Documents/Repositories/qmk:/qmk:rw edasque/qmk_firmware
+
 ```
 
 This will compile the targetted keyboard/keymap and leave it in your QMK directory for you to flash.
@@ -238,6 +241,7 @@ You can also add extra options at the end of the make command line, after the ta
 * `make COLOR=false` - turns off color output
 * `make SILENT=true` - turns off output besides errors/warnings
 * `make VERBOSE=true` - outputs all of the gcc stuff (not interesting, unless you need to debug)
+* `make EXTRAFLAGS=-E` - Preprocess the code without doing any compiling (useful if you are trying to debug #define commands)
 
 The make command itself also has some additional options, type `make --help` for more information. The most useful is probably `-jx`, which specifies that you want to compile using more than one CPU, the `x` represents the number of CPUs that you want to use. Setting that can greatly reduce the compile times, especially if you are compiling many keyboards/keymaps. I usually set it to one less than the number of CPUs that I have, so that I have some left for doing other things while it's compiling. Note that not all operating systems and make versions supports that option.
 
@@ -320,6 +324,18 @@ This enables MIDI sending and receiving with your keyboard. To enter MIDI send m
 
 This allows you to send unicode symbols via `UC(<unicode>)` in your keymap. Only codes up to 0x7FFF are currently supported.
 
+`UNICODEMAP_ENABLE`
+
+This allows sending unicode symbols using `X(<unicode>)` in your keymap. Codes
+up to 0xFFFFFFFF are supported, including emojis. You will need to maintain
+a separate mapping table in your keymap file.
+
+Known limitations:
+- Under Mac OS, only codes up to 0xFFFF are supported.
+- Under Linux ibus, only codes up to 0xFFFFF are supported (but anything important is still under this limit for now).
+
+Characters out of range supported by the OS will be ignored.
+
 `BLUETOOTH_ENABLE`
 
 This allows you to interface with a Bluefruit EZ-key to send keycodes wirelessly. It uses the D2 and D3 pins.
@@ -328,6 +344,14 @@ This allows you to interface with a Bluefruit EZ-key to send keycodes wirelessly
 
 This allows you output audio on the C6 pin (needs abstracting). See the [audio section](#driving-a-speaker---audio-support) for more information.
 
+`VARIABLE_TRACE`
+
+Use this to debug changes to variable values, see the [tracing variables](#tracing-variables) section for more information.
+
+`API_SYSEX_ENABLE`
+
+This enables using the Quantum SYSEX API to send strings (somewhere?)
+
 ### Customizing Makefile options on a per-keymap basis
 
 If your keymap directory has a file called `Makefile` (note the filename), any Makefile options you set in that file will take precedence over other Makefile options for your particular keyboard.
@@ -378,6 +402,7 @@ Instead of using `FNx` when defining `ACTION_*` functions, you can use `F(x)` -
 
 `TO(layer)` - Goes to a layer. This code is special, because it lets you go either up or down the stack -- just goes directly to the layer you want. So while other codes only let you go _up_ the stack (from layer 0 to layer 3, for example), `TO(2)` is going to get you to layer 2, no matter where you activate it from -- even if you're currently on layer 5. This gets activated on keydown (as soon as the key is pressed).
 
+
 ### Fun with modifier keys
 
 * `LSFT(kc)` - applies left Shift to *kc* (keycode) - `S(kc)` is an alias
@@ -527,7 +552,7 @@ This array specifies what actions shall be taken when a tap-dance key is in acti
 
 * `ACTION_TAP_DANCE_DOUBLE(kc1, kc2)`: Sends the `kc1` keycode when tapped once, `kc2` otherwise. When the key is held, the appropriate keycode is registered: `kc1` when pressed and held, `kc2` when tapped once, then pressed and held.
 * `ACTION_TAP_DANCE_FN(fn)`: Calls the specified function - defined in the user keymap - with the final tap count of the tap dance action.
-* `ACTION_TAP_DANCE_FN_ADVANCED(on_each_tap_fn, on_dance_finished_fn, on_reset_fn)`: Calls the first specified function - defined in the user keymap - on every tap, the second function on when the dance action finishes (like the previous option), and the last function when the tap dance action resets.
+* `ACTION_TAP_DANCE_FN_ADVANCED(on_each_tap_fn, on_dance_finished_fn, on_dance_reset_fn)`: Calls the first specified function - defined in the user keymap - on every tap, the second function on when the dance action finishes (like the previous option), and the last function when the tap dance action resets.
 
 The first option is enough for a lot of cases, that just want dual roles. For example, `ACTION_TAP_DANCE(KC_SPC, KC_ENT)` will result in `Space` being sent on single-tap, `Enter` otherwise.
 
@@ -824,7 +849,7 @@ And then, to assign this macro to a key on your keyboard layout, you just use `M
 
 ## Dynamic macros: record and replay macros in runtime
 
-In addition to the static macros described above, you may enable the dynamic macros which you may record while writing. They are forgotten as soon as the keyboard is unplugged. Only two such macros may be stored at the same time, with the total length of 128 keypresses.
+In addition to the static macros described above, you may enable the dynamic macros which you may record while writing. They are forgotten as soon as the keyboard is unplugged. Only two such macros may be stored at the same time, with the total length of 64 keypresses (by default).
 
 To enable them, first add a new element to the `planck_keycodes` enum -- `DYNAMIC_MACRO_RANGE`:
 
@@ -865,7 +890,7 @@ Add the following code to the very beginning of your `process_record_user()` fun
 
 To start recording the macro, press either `DYN_REC_START1` or `DYN_REC_START2`. To finish the recording, press the `_DYN` layer button. The handler awaits specifically for the `MO(_DYN)` keycode as the "stop signal" so please don't use any fancy ways to access this layer, use the regular `MO()` modifier. To replay the macro, press either `DYN_MACRO_PLAY1` or `DYN_MACRO_PLAY2`.
 
-If the LED-s start blinking during the recording with each keypress, it means there is no more space for the macro in the macro buffer. To fit the macro in, either make the other macro shorter (they share the same buffer) or increase the buffer size by setting the `DYNAMIC_MACRO_SIZE` preprocessor macro (default value: 256; please read the comments for it in the header).
+If the LED-s start blinking during the recording with each keypress, it means there is no more space for the macro in the macro buffer. To fit the macro in, either make the other macro shorter (they share the same buffer) or increase the buffer size by setting the `DYNAMIC_MACRO_SIZE` preprocessor macro (default value: 128; please read the comments for it in the header).
 
 For the details about the internals of the dynamic macros, please read the comments in the `dynamic_macro.h` header.
 
@@ -890,7 +915,33 @@ In `quantum/keymap_extras/`, you'll see various language files - these work the
 
 ## Unicode support
 
-You can currently send 4 hex digits with your OS-specific modifier key (RALT for OSX with the "Unicode Hex Input" layout) - this is currently limited to supporting one OS at a time, and requires a recompile for switching. 8 digit hex codes are being worked on. The keycode function is `UC(n)`, where *n* is a 4 digit hexidecimal. Enable from the Makefile.
+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\EnableHexNumpad` of type `REG_SZ` called `EnableHexNumpad`, 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](https://github.com/samhocevar/wincompose). Works reliably under many (all?) variations of Windows.
 
 ## Backlight Breathing
 
@@ -1115,12 +1166,12 @@ For this mod, you need an unused pin wiring to DI of WS2812 strip. After wiring
 
     RGBLIGHT_ENABLE = yes
 
-In order to use the underglow timer functions, you need to have `#define RGBLIGHT_TIMER` in your `config.h`, and have audio disabled (`AUDIO_ENABLE = no` in your Makefile).
+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_TIMER    // Require for fancier stuff (not compatible with audio)
+    #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
@@ -1136,20 +1187,278 @@ The firmware supports 5 different light effects, and the color (hue, saturation,
 
 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 a keyboard map does not include RESET, then, to get into DFU
+- 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 some bits.
+  requires unscrewing the bottom.
 - Messing with tmk_core / common files might make the keyboard
   inoperable
 - Too large a .hex file is trouble; `make dfu` will erase the block,
   test the size (oops, wrong order!), which errors out, failing to
-  flash the keyboard
+  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.
@@ -1267,3 +1576,22 @@ If there are problems with the tests, you can find the executable in the `./buil
 It's not yet possible to do a full integration test, where you would compile the whole firmware and define a keymap that you are going to test. However there are plans for doing that, because writing tests that way would probably be easier, at least for people that are not used to unit testing.
 
 In that model you would emulate the input, and expect a certain output from the emulated keyboard.
+
+# Tracing variables 
+
+Sometimes you might wonder why a variable gets changed and where, and this can be quite tricky to track down without having a debugger. It's of course possible to manually add print statements to track it, but you can also enable the variable trace feature. This works for both for variables that are changed by the code, and when the variable is changed by some memory corruption.
+
+To take the feature into use add `VARIABLE_TRACE=x` to the end of you make command. `x` represents the number of variables you want to trace, which is usually 1. 
+
+Then at a suitable place in the code, call `ADD_TRACED_VARIABLE`, to begin the tracing. For example to trace all the layer changes, you can do this
+```c
+void matrix_init_user(void) {
+  ADD_TRACED_VARIABLE("layer", &layer_state, sizeof(layer_state));
+}
+```
+
+This will add a traced variable named "layer" (the name is just for your information), which tracks the memory location of `layer_state`. It tracks 4 bytes (the size of `layer_state`), so any modification to the variable will be reported. By default you can not specify a size bigger than 4, but you can change it by adding `MAX_VARIABLE_TRACE_SIZE=x` to the end of the make command line.
+
+In order to actually detect changes to the variables you should call `VERIFY_TRACED_VARIABLES` around the code that you think that modifies the variable. If a variable is modified it will tell you between which two `VERIFY_TRACED_VARIABLES` calls the modification happened. You can then add more calls to track it down further. I don't recommend spamming the codebase with calls. It's better to start with a few, and then keep adding them in a binary search fashion. You can also delete the ones you don't need, as each call need to store the file name and line number in the ROM, so you can run out of memory if you add too many calls.
+
+Also remember to delete all the tracing code ones you have found the bug, as you wouldn't want to create a pull request with tracing code.