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qmk_firmware/docs/feature_joystick.md

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# Joystick :id=joystick
This feature provides game controller input as a joystick device supporting up to 6 axes and 32 buttons. Axes can be read either from an [ADC-capable input pin](adc_driver.md), or can be virtual, so that its value is provided by your code.
An analog device such as a [potentiometer](https://en.wikipedia.org/wiki/Potentiometer) found on an analog joystick's axes is based on a voltage divider, where adjusting the movable wiper controls the output voltage which can then be read by the microcontroller's ADC.
## Usage :id=usage
Add the following to your `rules.mk`:
```make
JOYSTICK_ENABLE = yes
```
By default the joystick driver is `analog`, but you can change this with:
```make
JOYSTICK_DRIVER = digital
```
## Configuration :id=configuration
By default, two axes and eight buttons are defined, with a reported resolution of 8 bits (-127 to +127). This can be changed in your `config.h`:
```c
// Min 0, max 32
#define JOYSTICK_BUTTON_COUNT 16
// Min 0, max 6: X, Y, Z, Rx, Ry, Rz
#define JOYSTICK_AXIS_COUNT 3
// Min 8, max 16
#define JOYSTICK_AXIS_RESOLUTION 10
```
?> You must define at least one button or axis. Also note that the maximum ADC resolution of the supported AVR MCUs is 10-bit, and 12-bit for most STM32 MCUs.
### Axes :id=axes
When defining axes for your joystick, you must provide a definition array typically in your `keymap.c`.
For instance, the below example configures two axes. The X axis is read from the `A4` pin. With the default axis resolution of 8 bits, the range of values between 900 and 575 are scaled to -127 through 0, and values 575 to 285 are scaled to 0 through 127. The Y axis is configured as a virtual axis, and its value is not read from any pin. Instead, the user must update the axis value programmatically.
```c
joystick_config_t joystick_axes[JOYSTICK_AXIS_COUNT] = {
JOYSTICK_AXIS_IN(A4, 900, 575, 285),
JOYSTICK_AXIS_VIRTUAL
};
```
Axes can be configured using one of the following macros:
* `JOYSTICK_AXIS_IN(input_pin, low, rest, high)`
The ADC samples the provided pin. `low`, `high` and `rest` correspond to the minimum, maximum, and resting (or centered) analog values of the axis, respectively.
* `JOYSTICK_AXIS_IN_OUT(input_pin, output_pin, low, rest, high)`
Same as `JOYSTICK_AXIS_IN()`, but the provided `output_pin` will be pulled high before `input_pin` is read.
* `JOYSTICK_AXIS_IN_OUT_GROUND(input_pin, output_pin, ground_pin, low, rest, high)`
Same as `JOYSTICK_AXIS_IN_OUT()`, but the provided `ground_pin` will be pulled low before reading from `input_pin`.
* `JOYSTICK_AXIS_VIRTUAL`
No ADC reading is performed. The value should be provided by user code.
The `low` and `high` values can be swapped to effectively invert the axis.
#### Virtual Axes :id=virtual-axes
The following example adjusts two virtual axes (X and Y) based on keypad presses, with `KC_P0` as a precision modifier:
```c
joystick_config_t joystick_axes[JOYSTICK_AXIS_COUNT] = {
JOYSTICK_AXIS_VIRTUAL, // x
JOYSTICK_AXIS_VIRTUAL // y
};
static bool precision = false;
static uint16_t precision_mod = 64;
static uint16_t axis_val = 127;
bool process_record_user(uint16_t keycode, keyrecord_t *record) {
int16_t precision_val = axis_val;
if (precision) {
precision_val -= precision_mod;
}
switch (keycode) {
case KC_P8:
joystick_set_axis(1, record->event.pressed ? -precision_val : 0);
return false;
case KC_P2:
joystick_set_axis(1, record->event.pressed ? precision_val : 0);
return false;
case KC_P4:
joystick_set_axis(0, record->event.pressed ? -precision_val : 0);
return false;
case KC_P6:
joystick_set_axis(0, record->event.pressed ? precision_val : 0);
return false;
case KC_P0:
precision = record->event.pressed;
return false;
}
return true;
}
```
## Keycodes :id=keycodes
|Key |Aliases|Description|
|-----------------------|-------|-----------|
|`QK_JOYSTICK_BUTTON_0` |`JS_0` |Button 0 |
|`QK_JOYSTICK_BUTTON_1` |`JS_1` |Button 1 |
|`QK_JOYSTICK_BUTTON_2` |`JS_2` |Button 2 |
|`QK_JOYSTICK_BUTTON_3` |`JS_3` |Button 3 |
|`QK_JOYSTICK_BUTTON_4` |`JS_4` |Button 4 |
|`QK_JOYSTICK_BUTTON_5` |`JS_5` |Button 5 |
|`QK_JOYSTICK_BUTTON_6` |`JS_6` |Button 6 |
|`QK_JOYSTICK_BUTTON_7` |`JS_7` |Button 7 |
|`QK_JOYSTICK_BUTTON_8` |`JS_8` |Button 8 |
|`QK_JOYSTICK_BUTTON_9` |`JS_9` |Button 9 |
|`QK_JOYSTICK_BUTTON_10`|`JS_10`|Button 10 |
|`QK_JOYSTICK_BUTTON_11`|`JS_11`|Button 11 |
|`QK_JOYSTICK_BUTTON_12`|`JS_12`|Button 12 |
|`QK_JOYSTICK_BUTTON_13`|`JS_13`|Button 13 |
|`QK_JOYSTICK_BUTTON_14`|`JS_14`|Button 14 |
|`QK_JOYSTICK_BUTTON_15`|`JS_15`|Button 15 |
|`QK_JOYSTICK_BUTTON_16`|`JS_16`|Button 16 |
|`QK_JOYSTICK_BUTTON_17`|`JS_17`|Button 17 |
|`QK_JOYSTICK_BUTTON_18`|`JS_18`|Button 18 |
|`QK_JOYSTICK_BUTTON_19`|`JS_19`|Button 19 |
|`QK_JOYSTICK_BUTTON_20`|`JS_20`|Button 20 |
|`QK_JOYSTICK_BUTTON_21`|`JS_21`|Button 21 |
|`QK_JOYSTICK_BUTTON_22`|`JS_22`|Button 22 |
|`QK_JOYSTICK_BUTTON_23`|`JS_23`|Button 23 |
|`QK_JOYSTICK_BUTTON_24`|`JS_24`|Button 24 |
|`QK_JOYSTICK_BUTTON_25`|`JS_25`|Button 25 |
|`QK_JOYSTICK_BUTTON_26`|`JS_26`|Button 26 |
|`QK_JOYSTICK_BUTTON_27`|`JS_27`|Button 27 |
|`QK_JOYSTICK_BUTTON_28`|`JS_28`|Button 28 |
|`QK_JOYSTICK_BUTTON_29`|`JS_29`|Button 29 |
|`QK_JOYSTICK_BUTTON_30`|`JS_30`|Button 30 |
|`QK_JOYSTICK_BUTTON_31`|`JS_31`|Button 31 |
## API :id=api
### `struct joystick_t` :id=api-joystick-t
Contains the state of the joystick.
#### Members :id=api-joystick-t-members
- `uint8_t buttons[]`
A bit-packed array containing the joystick button states. The size is calculated as `(JOYSTICK_BUTTON_COUNT - 1) / 8 + 1`.
- `int16_t axes[]`
An array of analog values for each defined axis.
- `bool dirty`
Whether the current state needs to be sent to the host.
---
### `struct joystick_config_t` :id=api-joystick-config-t
Describes a single axis.
#### Members :id=api-joystick-config-t-members
- `pin_t output_pin`
A pin to set as output high when reading the analog value, or `JS_VIRTUAL_AXIS`.
- `pin_t input_pin`
The pin to read the analog value from, or `JS_VIRTUAL_AXIS`.
- `pin_t ground_pin`
A pin to set as output low when reading the analog value, or `JS_VIRTUAL_AXIS`.
- `uint16_t min_digit`
The minimum analog value.
- `uint16_t mid_digit`
The resting or midpoint analog value.
- `uint16_t max_digit`
The maximum analog value.
---
### `void joystick_flush(void)` :id=api-joystick-flush
Send the joystick report to the host, if it has been marked as dirty.
---
### `void register_joystick_button(uint8_t button)` :id=api-register-joystick-button
Set the state of a button, and flush the report.
#### Arguments :id=api-register-joystick-button-arguments
- `uint8_t button`
The index of the button to press, from 0 to 31.
---
### `void unregister_joystick_button(uint8_t button)` :id=api-unregister-joystick-button
Reset the state of a button, and flush the report.
#### Arguments :id=api-unregister-joystick-button-arguments
- `uint8_t button`
The index of the button to release, from 0 to 31.
---
### `int16_t joystick_read_axis(uint8_t axis)` :id=api-joystick-read-axis
Sample and process the analog value of the given axis.
#### Arguments :id=api-joystick-read-axis-arguments
- `uint8_t axis`
The axis to read.
#### Return Value :id=api-joystick-read-axis-return
A signed 16-bit integer, where 0 is the resting or mid point.
### `void joystick_set_axis(uint8_t axis, int16_t value)` :id=api-joystick-set-axis
Set the value of the given axis.
#### Arguments :id=api-joystick-set-axis-arguments
- `uint8_t axis`
The axis to set the value of.
- `int16_t value`
The value to set.
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