#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, or can be virtual, so that its value is provided by your code.

An analog device such as a 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:

JOYSTICK_ENABLE = yes

By default the joystick driver is analog, but you can change this with:

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:

// 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.

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:

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

#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.