Hid joystick interface

common_features.mk

@@ -516,3 +516,10 @@ ifeq ($(strip $(AUTO_SHIFT_ENABLE)), yes)
         OPT_DEFS += -DAUTO_SHIFT_MODIFIERS
     endif
 endif
+
+ifeq ($(strip $(JOYSTICK_ENABLE)), yes)
+    OPT_DEFS += -DJOYSTICK_ENABLE
+    SRC += $(QUANTUM_DIR)/process_keycode/process_joystick.c
+    SRC += $(QUANTUM_DIR)/joystick.c
+    SRC += analog.c
+endif

docs/_summary.md

@@ -98,6 +98,7 @@
     * [DIP Switch](feature_dip_switch.md)
     * [Encoders](feature_encoders.md)
     * [Haptic Feedback](feature_haptic_feedback.md)
+    * [Joystick](feature_joystick.md)
     * [Proton C Conversion](proton_c_conversion.md)
     * [PS/2 Mouse](feature_ps2_mouse.md)
     * [Split Keyboard](feature_split_keyboard.md)

docs/feature_joystick.md

@@ -0,0 +1,145 @@
+## Joystick
+
+The keyboard can be made to be recognized as a joystick HID device by the operating system.
+
+This is enabled by adding the following to `rules.mk`:
+
+```makefile
+JOYSTICK_ENABLE = yes
+```
+
+!> 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
+
+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 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 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;
+}
+```
+
+### 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.

drivers/avr/analog.c

@@ -97,10 +97,11 @@ uint8_t pinToMux(pin_t pin) {
 #endif
             // clang-format on
     }
+    return 0;
 }
 
 int16_t adc_read(uint8_t mux) {
-    uint8_t low;
+    uint16_t low;
 
     // Enable ADC and configure prescaler
     ADCSRA = _BV(ADEN) | ADC_PRESCALER;
@@ -128,5 +129,10 @@ int16_t adc_read(uint8_t mux) {
     // Must read LSB first
     low = ADCL;
     // Must read MSB only once!
-    return (ADCH << 8) | low;
+    low |= (ADCH << 8);
+
+    // turn off the ADC
+    ADCSRA &= ~(1 << ADEN);
+
+    return low;
 }

keyboards/handwired/onekey/keymaps/joystick/config.h

@@ -0,0 +1,3 @@
+#pragma once
+#define JOYSTICK_AXES_COUNT 2
+#define JOYSTICK_BUTTON_COUNT 1

keyboards/handwired/onekey/keymaps/joystick/keymap.c

@@ -0,0 +1,25 @@
+#include QMK_KEYBOARD_H
+
+#include "joystick.h"
+
+#ifndef ADC_PIN
+#    define ADC_PIN F6
+#endif
+
+const uint16_t PROGMEM keymaps[][MATRIX_ROWS][MATRIX_COLS] = {
+  LAYOUT( JS_BUTTON0 )
+};
+
+void matrix_scan_user() {
+  int16_t val = (((uint32_t)timer_read()%5000 - 2500) * 255) / 5000;
+  if (val != joystick_status.axes[1]) {
+    joystick_status.axes[1] = val;
+    joystick_status.status |= JS_UPDATED;
+  }
+}
+
+//joystick config
+joystick_config_t joystick_axes[JOYSTICK_AXES_COUNT] = {
+    [0] = JOYSTICK_AXIS_IN(ADC_PIN, 0, 512, 1023)
+  , [1] = JOYSTICK_AXIS_VIRTUAL
+};

keyboards/handwired/onekey/keymaps/joystick/rules.mk

@@ -0,0 +1 @@
+JOYSTICK_ENABLE = yes

quantum/joystick.c

@@ -0,0 +1,13 @@
+#include "joystick.h"
+
+joystick_t joystick_status = {.buttons = {0},
+                              .axes =
+                                  {
+#if JOYSTICK_AXES_COUNT > 0
+                                      0
+#endif
+                                  },
+                              .status = 0};
+
+// array defining the reading of analog values for each axis
+__attribute__((weak)) joystick_config_t joystick_axes[JOYSTICK_AXES_COUNT] = {};

quantum/joystick.h

@@ -0,0 +1,54 @@
+#pragma once
+
+#ifndef JOYSTICK_BUTTON_COUNT
+#    define JOYSTICK_BUTTON_COUNT 8
+#endif
+
+#ifndef JOYSTICK_AXES_COUNT
+#    define JOYSTICK_AXES_COUNT 4
+#endif
+
+#include "quantum.h"
+
+#include <stdint.h>
+
+// configure on input_pin of the joystick_axes array entry to JS_VIRTUAL_AXIS
+// to prevent it from being read from the ADC. This allows outputing forged axis value.
+//
+#define JS_VIRTUAL_AXIS 0xFF
+
+#define JOYSTICK_AXIS_VIRTUAL \
+    { JS_VIRTUAL_AXIS, JS_VIRTUAL_AXIS, JS_VIRTUAL_AXIS, 0, 1023 }
+#define JOYSTICK_AXIS_IN(INPUT_PIN, LOW, REST, HIGH) \
+    { JS_VIRTUAL_AXIS, INPUT_PIN, JS_VIRTUAL_AXIS, LOW, REST, HIGH }
+#define JOYSTICK_AXIS_IN_OUT(INPUT_PIN, OUTPUT_PIN, LOW, REST, HIGH) \
+    { OUTPUT_PIN, INPUT_PIN, JS_VIRTUAL_AXIS, LOW, REST, HIGH }
+#define JOYSTICK_AXIS_IN_OUT_GROUND(INPUT_PIN, OUTPUT_PIN, GROUND_PIN, LOW, REST, HIGH) \
+    { OUTPUT_PIN, INPUT_PIN, GROUND_PIN, LOW, REST, HIGH }
+
+typedef struct {
+    pin_t output_pin;
+    pin_t input_pin;
+    pin_t ground_pin;
+
+    // the AVR ADC offers 10 bit precision, with significant bits on the higher part
+    uint16_t min_digit;
+    uint16_t mid_digit;
+    uint16_t max_digit;
+} joystick_config_t;
+
+extern joystick_config_t joystick_axes[JOYSTICK_AXES_COUNT];
+
+enum joystick_status { JS_INITIALIZED = 1, JS_UPDATED = 2 };
+
+typedef struct {
+    uint8_t buttons[JOYSTICK_BUTTON_COUNT / 8 + 1];
+
+    int16_t axes[JOYSTICK_AXES_COUNT];
+    uint8_t status : 2;
+} joystick_t;
+
+extern joystick_t joystick_status;
+
+// to be implemented in the hid protocol library
+void send_joystick_packet(joystick_t *joystick);