qmk_firmware/docs/feature_joystick.md
James Young c66df16644
2020 November 28 Breaking Changes Update (#11053)
* Branch point for 2020 November 28 Breaking Change                                                

* Remove matrix_col_t to allow MATRIX_ROWS > 32 (#10183)                                           

* Add support for soft serial to ATmega32U2 (#10204)                                               

* Change MIDI velocity implementation to allow direct control of velocity value (#9940)            

* Add ability to build a subset of all keyboards based on platform.                                

* Actually use eeprom_driver_init().                                                               

* Make bootloader_jump weak for ChibiOS. (#10417)                                                  

* Joystick 16-bit support (#10439)                                                                 

* Per-encoder resolutions (#10259)                                                                 

* Share button state from mousekey to pointing_device (#10179)                                     

* Add hotfix for chibios keyboards not wake (#10088)                                               

* Add advanced/efficient RGB Matrix Indicators (#8564)                                             

* Naming change.                                                                                   

* Support for STM32 GPIOF,G,H,I,J,K (#10206)                                                       

* Add milc as a dependency and remove the installed milc (#10563)                                  

* ChibiOS upgrade: early init conversions (#10214)                                                 

* ChibiOS upgrade: configuration file migrator (#9952)                                             

* Haptic and solenoid cleanup (#9700)                                                              

* XD75 cleanup (#10524)                                                                            

* OLED display update interval support (#10388)                                                    

* Add definition based on currently-selected serial driver. (#10716)                               

* New feature: Retro Tapping per key (#10622)                                                      

* Allow for modification of output RGB values when using rgblight/rgb_matrix. (#10638)             

* Add housekeeping task callbacks so that keyboards/keymaps are capable of executing code for each main loop iteration. (#10530)

* Rescale both ChibiOS and AVR backlighting.                                                       

* Reduce Helix keyboard build variation (#8669)                                                    

* Minor change to behavior allowing display updates to continue between task ticks (#10750)        

* Some GPIO manipulations in matrix.c change to atomic. (#10491)                                   

* qmk cformat (#10767)                                                                             

* [Keyboard] Update the Speedo firmware for v3.0 (#10657)                                          

* Maartenwut/Maarten namechange to evyd13/Evy (#10274)                                             

* [quantum] combine repeated lines of code (#10837)                                                

* Add step sequencer feature (#9703)                                                               

* aeboards/ext65 refactor (#10820)                                                                 

* Refactor xelus/dawn60 for Rev2 later (#10584)                                                    

* add DEBUG_MATRIX_SCAN_RATE_ENABLE to common_features.mk (#10824)                                 

* [Core] Added `add_oneshot_mods` & `del_oneshot_mods` (#10549)                                    

* update chibios os usb for the otg driver (#8893)                                                 

* Remove HD44780 References, Part 4 (#10735)                                                       

* [Keyboard] Add Valor FRL TKL (+refactor) (#10512)                                                

* Fix cursor position bug in oled_write_raw functions (#10800)                                     

* Fixup version.h writing when using SKIP_VERSION=yes (#10972)                                     

* Allow for certain code in the codebase assuming length of string. (#10974)                       

* Add AT90USB support for serial.c (#10706)                                                        

* Auto shift: support repeats and early registration (#9826)                                       

* Rename ledmatrix.h to match .c file (#7949)                                                      

* Split RGB_MATRIX_ENABLE into _ENABLE and _DRIVER (#10231)                                        

* Split LED_MATRIX_ENABLE into _ENABLE and _DRIVER (#10840)                                        

* Merge point for 2020 Nov 28 Breaking Change
2020-11-28 12:02:18 -08:00

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Markdown

## Joystick
The keyboard can be made to be recognized as a joystick HID device by the operating system.
This is enabled by adding `JOYSTICK_ENABLE` to `rules.mk`. You can set this value to `analog`, `digital`, or `no`.
!> Joystick support is not currently available on V-USB devices.
The joystick feature provides two services:
* reading analog input devices (eg. potentiometers)
* sending gamepad HID reports
Both services can be used without the other, depending on whether you just want to read a device but not send gamepad reports (for volume control for instance)
or send gamepad reports based on values computed by the keyboard.
### Analog Input
To use analog input you must first enable it in `rules.mk`:
```makefile
JOYSTICK_ENABLE = analog
```
An analog device such as a potentiometer found on a gamepad's analog axes is based on a [voltage divider](https://en.wikipedia.org/wiki/Voltage_divider).
It is composed of three connectors linked to the ground, the power input and power output (usually the middle one). The power output holds the voltage that varies based on the position of the cursor,
which value will be read using your MCU's [ADC](https://en.wikipedia.org/wiki/Analog-to-digital_converter).
Depending on which pins are already used by your keyboard's matrix, the rest of the circuit can get a little bit more complicated,
feeding the power input and ground connection through pins and using diodes to avoid bad interactions with the matrix scanning procedures.
### Configuring the Joystick
By default, two axes and eight buttons are defined. This can be changed in your `config.h`:
```c
// Max 32
#define JOYSTICK_BUTTON_COUNT 16
// Max 6: X, Y, Z, Rx, Ry, Rz
#define JOYSTICK_AXES_COUNT 3
```
When defining axes for your joystick, you have to provide a definition array. You can do this from your keymap.c file.
A joystick will either be read from an input pin that allows the use of the ADC, or can be virtual, so that its value is provided by your code.
You have to define an array of type ''joystick_config_t'' and of proper size.
There are three ways for your circuit to work with the ADC, that relies on the use of 1, 2 or 3 pins of the MCU:
* 1 pin: your analog device is directly connected to your device GND and VCC. The only pin used is the ADC pin of your choice.
* 2 pins: your analog device is powered through a pin that allows toggling it on or off. The other pin is used to read the input value through the ADC.
* 3 pins: both the power input and ground are connected to pins that must be set to a proper state before reading and restored afterwards.
The configuration of each axis is performed using one of four macros:
* `JOYSTICK_AXIS_VIRTUAL`: no ADC reading must be performed, that value will be provided by keyboard/keymap-level code
* `JOYSTICK_AXIS_IN(INPUT_PIN, LOW, REST, HIGH)`: a voltage will be read on the provided pin, which must be an ADC-capable pin.
* `JOYSTICK_AXIS_IN_OUT(INPUT_PIN, OUTPUT_PIN, LOW, REST, HIGH)`: the provided `OUTPUT_PIN` will be set high before `INPUT_PIN` is read.
* `JOYSTICK_AXIS_IN_OUT_GROUND(INPUT_PIN, OUTPUT_PIN, GROUND_PIN, LOW, REST, HIGH)`: the `OUTPUT_PIN` will be set high and `GROUND_PIN` will be set low before reading from `INPUT_PIN`.
In any case where an ADC reading takes place (when `INPUT_PIN` is provided), additional `LOW`, `REST` and `HIGH` parameters are used.
These implement the calibration of the analog device by defining the range of read values that will be mapped to the lowest, resting position and highest possible value for the axis (-127 to 127).
In practice, you have to provide the lowest/highest raw ADC reading, and the raw reading at resting position, when no deflection is applied. You can provide inverted `LOW` and `HIGH` to invert the axis.
For instance, an axes configuration can be defined in the following way:
```c
//joystick config
joystick_config_t joystick_axes[JOYSTICK_AXES_COUNT] = {
[0] = JOYSTICK_AXIS_IN_OUT_GROUND(A4, B0, A7, 900, 575, 285),
[1] = JOYSTICK_AXIS_VIRTUAL
};
```
When the ADC reads 900 or higher, the returned axis value will be -127, whereas it will be 127 when the ADC reads 285 or lower. Zero is returned when 575 is read.
In this example, the first axis will be read from the `A4` pin while `B0` is set high and `A7` is set low, using `analogReadPin()`, whereas the second axis will not be read.
In order to give a value to the second axis, you can do so in any customizable entry point: as an action, in `process_record_user()` or in `matrix_scan_user()`, or even in `joystick_task()` which is called even when no key has been pressed.
You assign a value by writing to `joystick_status.axes[axis_index]` a signed 8-bit value (ranging from -127 to 127). Then it is necessary to assign the flag `JS_UPDATED` to `joystick_status.status` in order for an updated HID report to be sent.
The following example writes two axes based on keypad presses, with `KC_P5` as a precision modifier:
```c
#ifdef ANALOG_JOYSTICK_ENABLE
static uint8_t precision_val = 70;
static uint8_t axesFlags = 0;
enum axes {
Precision = 1,
Axis1High = 2,
Axis1Low = 4,
Axis2High = 8,
Axis2Low = 16
};
#endif
bool process_record_user(uint16_t keycode, keyrecord_t *record) {
switch(keycode) {
#ifdef ANALOG_JOYSTICK_ENABLE
// virtual joystick
# if JOYSTICK_AXES_COUNT > 1
case KC_P8:
if (record->event.pressed) {
axesFlags |= Axis2Low;
} else {
axesFlags &= ~Axis2Low;
}
joystick_status.status |= JS_UPDATED;
break;
case KC_P2:
if (record->event.pressed) {
axesFlags |= Axis2High;
} else {
axesFlags &= ~Axis2High;
}
joystick_status.status |= JS_UPDATED;
break;
# endif
case KC_P4:
if (record->event.pressed) {
axesFlags |= Axis1Low;
} else {
axesFlags &= ~Axis1Low;
}
joystick_status.status |= JS_UPDATED;
break;
case KC_P6:
if (record->event.pressed) {
axesFlags |= Axis1High;
} else {
axesFlags &= ~Axis1High;
}
joystick_status.status |= JS_UPDATED;
break;
case KC_P5:
if (record->event.pressed) {
axesFlags |= Precision;
} else {
axesFlags &= ~Precision;
}
joystick_status.status |= JS_UPDATED;
break;
#endif
}
return true;
}
```
### Axis Resolution
By default, the resolution of each axis is 8 bit, giving a range of -127 to +127. If you need higher precision, you can increase it by defining eg. `JOYSTICK_AXES_RESOLUTION 12` in your `config.h`. The resolution must be between 8 and 16.
Note that the supported AVR MCUs have a 10-bit ADC, and 12-bit for most STM32 MCUs.
### Triggering Joystick Buttons
Joystick buttons are normal Quantum keycodes, defined as `JS_BUTTON0` to `JS_BUTTON31`, depending on the number of buttons you have configured.
To trigger a joystick button, just add the corresponding keycode to your keymap.