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+# PS/2 Mouse Support :id=ps2-mouse-support
+
+Its possible to hook up a PS/2 mouse (for example touchpads or trackpoints) to your keyboard as a composite device.
+
+To hook up a Trackpoint, you need to obtain a Trackpoint module (i.e. harvest from a Thinkpad keyboard), identify the function of each pin of the module, and make the necessary circuitry between controller and Trackpoint module. For more information, please refer to [Trackpoint Hardware](https://deskthority.net/wiki/TrackPoint_Hardware) page on Deskthority Wiki.
+
+There are three available modes for hooking up PS/2 devices: USART (best), interrupts (better) or busywait (not recommended).
+
+## The Circuitry between Trackpoint and Controller :id=the-circuitry-between-trackpoint-and-controller
+
+To get the things working, a 4.7K drag is needed between the two lines DATA and CLK and the line 5+. 
+
+```
+
+          DATA ----------+--------- PIN
+                         |
+                        4.7K
+                         |
+MODULE    5+  --------+--+--------- PWR   CONTROLLER
+                      |
+                     4.7K
+                      |    
+          CLK   ------+------------ PIN
+```
+
+
+## Busywait Version :id=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:
+
+```make
+PS2_MOUSE_ENABLE = yes
+PS2_USE_BUSYWAIT = yes
+```
+
+In your keyboard config.h:
+
+```c
+#ifdef PS2_USE_BUSYWAIT
+#   define PS2_CLOCK_PIN   D1
+#   define PS2_DATA_PIN    D2
+#endif
+```
+
+### Interrupt Version (AVR/ATMega32u4) :id=interrupt-version-avr
+
+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:
+
+```make
+PS2_MOUSE_ENABLE = yes
+PS2_USE_INT = yes
+```
+
+In your keyboard config.h:
+
+```c
+#ifdef PS2_USE_INT
+#define PS2_CLOCK_PIN   D2
+#define PS2_DATA_PIN    D5
+
+#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
+```
+
+### Interrupt Version (ARM chibios) :id=interrupt-version-chibios
+
+Pretty much any two pins can be used for the (software) interrupt variant on ARM cores. The example below uses A8 for clock, and A9 for data.
+
+In rules.mk:
+
+```
+PS2_MOUSE_ENABLE = yes
+PS2_USE_INT = yes
+```
+
+In your keyboard config.h:
+
+```c
+#define PS2_CLOCK_PIN A8
+#define PS2_DATA_PIN  A9
+```
+
+And in the chibios specifig halconf.h:
+```c
+#define PAL_USE_CALLBACKS TRUE
+```
+
+
+### USART Version :id=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:
+
+```make
+PS2_MOUSE_ENABLE = yes
+PS2_USE_USART = yes
+```
+
+In your keyboard config.h:
+
+```c
+#ifdef PS2_USE_USART
+#define PS2_CLOCK_PIN   D5
+#define PS2_DATA_PIN    D2
+
+/* 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
+```
+
+## Additional Settings :id=additional-settings
+
+### PS/2 Mouse Features :id=ps2-mouse-features
+
+These enable settings supported by the PS/2 mouse protocol.
+
+```c
+/* 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
+
+```c
+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 :id=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).
+
+```c
+#define PS2_MOUSE_X_MULTIPLIER 3
+#define PS2_MOUSE_Y_MULTIPLIER 3
+#define PS2_MOUSE_V_MULTIPLIER 1
+```
+
+### Scroll Button :id=scroll-button
+
+If you're using a trackpoint, you will likely want to be able to use it for scrolling.
+It's 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:
+
+```c
+#define PS2_MOUSE_SCROLL_BTN_MASK (1<<PS2_MOUSE_BTN_MIDDLE) /* Default */
+```
+
+To disable the scroll button feature:
+
+```c
+#define PS2_MOUSE_SCROLL_BTN_MASK 0
+```
+
+The available buttons are:
+
+```c
+#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.
+
+```c
+#define PS2_MOUSE_SCROLL_BTN_SEND 300 /* Default */
+```
+
+To disable sending the scroll buttons:
+
+```c
+#define PS2_MOUSE_SCROLL_BTN_SEND 0
+```
+
+Fine control over the scrolling is supported with the following defines:
+
+```c
+#define PS2_MOUSE_SCROLL_DIVISOR_H 2
+#define PS2_MOUSE_SCROLL_DIVISOR_V 2
+```
+
+### Invert Mouse buttons :id=invert-buttons
+
+To invert the left & right buttons you can put:
+
+```c
+#define PS2_MOUSE_INVERT_BUTTONS
+```
+
+into config.h.
+
+### Invert Mouse and Scroll Axes :id=invert-mouse-and-scroll-axes
+
+To invert the X and Y axes you can put:
+
+```c
+#define PS2_MOUSE_INVERT_X
+#define PS2_MOUSE_INVERT_Y
+```
+
+into config.h.
+
+To reverse the scroll axes you can put:
+
+```c
+#define PS2_MOUSE_INVERT_H
+#define PS2_MOUSE_INVERT_V
+```
+
+into config.h.
+
+### Rotate Mouse Axes :id=rotate-mouse-axes
+
+Transform the output of the device with a clockwise rotation of 90, 180, or 270
+degrees.
+
+When compensating for device orientation, rotate the output the same amount in
+the opposite direction.  E.g. if the normal device orientation is considered to
+be North-facing, compensate as follows:
+
+```c
+#define PS2_MOUSE_ROTATE 270 /* Compensate for East-facing device orientation. */
+```
+```c
+#define PS2_MOUSE_ROTATE 180 /* Compensate for South-facing device orientation. */
+```
+```c
+#define PS2_MOUSE_ROTATE 90 /* Compensate for West-facing device orientation. */
+```
+
+### Debug Settings :id=debug-settings
+
+To debug the mouse, add `debug_mouse = true` or enable via bootmagic.
+
+```c
+/* To debug the mouse reports */
+#define PS2_MOUSE_DEBUG_HID
+#define PS2_MOUSE_DEBUG_RAW
+```
+
+### Movement Hook :id=movement-hook
+
+Process mouse movement in the keymap before it is sent to the host.  Example
+uses include filtering noise, adding acceleration, and automatically activating
+a layer.  To use, define the following function in your keymap:
+
+```c
+void ps2_mouse_moved_user(report_mouse_t *mouse_report);
+```