# PS/2 Mouse Support {#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 {#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 {#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_ENABLE = yes
PS2_DRIVER = busywait
```

In your keyboard config.h:

```c
#ifdef PS2_DRIVER_BUSYWAIT
# define PS2_CLOCK_PIN   D1
# define PS2_DATA_PIN    D2
#endif
```

### Interrupt Version (AVR/ATMega32u4) {#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_ENABLE = yes
PS2_DRIVER = interrupt
```

In your keyboard config.h:

```c
#ifdef PS2_DRIVER_INTERRUPT
#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) {#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_ENABLE = yes
PS2_DRIVER = interrupt
```

In your keyboard `config.h`:

```c
#define PS2_CLOCK_PIN A8
#define PS2_DATA_PIN  A9
```

And in the ChibiOS specific `halconf.h`:

```c
#pragma once

#define PAL_USE_CALLBACKS TRUE // [!code focus]

#include_next <halconf.h>
```

### USART Version {#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_ENABLE = yes
PS2_DRIVER = usart
```

In your keyboard config.h:

```c
#ifdef PS2_DRIVER_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
```

### RP2040 PIO Version {#rp2040-pio-version}

The `PIO` subsystem is a Raspberry Pi RP2040 specific implementation, using the integrated PIO peripheral and is therefore only available on this MCU.

There are strict requirements for pin ordering but any pair of GPIO pins can be used. The GPIO used for clock must be directly after data, see the included info.json snippet for an example of correct order.

You may optionally switch the PIO peripheral used with the following define in config.h:
```c
#define PS2_PIO_USE_PIO1 // Force the usage of PIO1 peripheral, by default the PS2 implementation uses the PIO0 peripheral
```

Example info.json content:

```json
    "ps2": {
        "clock_pin": "GP1",
        "data_pin": "GP0",
        "driver": "vendor",
        "enabled": true,
        "mouse_enabled": true
    }
```

## Additional Settings {#additional-settings}

### PS/2 Mouse Features {#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 {#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 {#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 {#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 {#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 {#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 {#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 {#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);
```