add support for hid gamepad interface

add documentation for HID joystick
Add joystick_task to read analog axes values even when no key is pressed or release. update doc
Update docs/feature_joystick.md
Manage pin setup and read to maintain matrix scan after analog read

quantum/joystick.c

@@ -0,0 +1,11 @@
+#include "joystick.h"
+
+joystick_t joystick_status = { 
+  .buttons = {0},
+  .axes = {0},
+  .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 +1,48 @@
+#ifndef JOYSTICK_H
+#define JOYSTICK_H
+
+#ifndef JOYSTICK_BUTTON_COUNT
+#define JOYSTICK_BUTTON_COUNT 8
+#endif
+
+#ifndef JOYSTICK_AXES_COUNT
+#define JOYSTICK_AXES_COUNT 4
+#endif
+
+#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
+
+typedef struct {
+  uint8_t output_pin;
+  uint8_t input_pin;
+  
+  //the AVR ADC offers 10 bit precision, with significant bits on the higher part
+  uint16_t min_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];
+  
+  int8_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);
+
+#endif //JOYSTICK_H

quantum/process_keycode/process_joystick.c

@@ -0,0 +1,79 @@
+#include "process_joystick.h"
+
+#include <quantum/joystick.h>
+#include <quantum/quantum_keycodes.h>
+
+#ifdef __AVR__
+# include <drivers/avr/analog.h>
+#endif
+
+#include <string.h>
+
+bool process_joystick_buttons(uint16_t keycode, keyrecord_t *record);
+
+bool process_joystick(uint16_t keycode, keyrecord_t *record){
+  
+  if (process_joystick_buttons(keycode, record) 
+    && (joystick_status.status & JS_UPDATED)>0){
+    send_joystick_packet(&joystick_status);
+    joystick_status.status &= ~JS_UPDATED;
+  }
+  
+  return true;
+}
+
+__attribute__ ((weak))
+void joystick_task(void){
+  if (process_joystick_analog() && (joystick_status.status & JS_UPDATED)){
+    send_joystick_packet(&joystick_status);
+    joystick_status.status &= ~JS_UPDATED;
+  }
+}
+
+bool process_joystick_buttons(uint16_t keycode, keyrecord_t *record){
+  
+  if (keycode < JS_BUTTON0 || keycode > JS_BUTTON_MAX){
+    return true;
+  } else {
+    if (record->event.pressed){
+      joystick_status.buttons[(keycode-JS_BUTTON0)/8] |= 1<<(keycode%8);
+    } else {
+      joystick_status.buttons[(keycode-JS_BUTTON0)/8] &= ~(1<<(keycode%8));
+    }
+    
+    joystick_status.status |= JS_UPDATED;
+  }
+  
+  return true;
+}
+
+__attribute__ ((weak))
+bool process_joystick_analog(){
+#if JOYSTICK_AXES_COUNT > 0
+  for (int axis_index=0 ; axis_index<JOYSTICK_AXES_COUNT ; ++axis_index){
+    if (joystick_axes[axis_index].output_pin==JS_VIRTUAL_AXIS || joystick_axes[axis_index].input_pin==JS_VIRTUAL_AXIS){
+      continue;
+    }
+    
+    setPinOutput(joystick_axes[axis_index].output_pin);
+    writePinHigh(joystick_axes[axis_index].output_pin);
+    
+    //disable pull-up resistance
+    setPinInput(joystick_axes[axis_index].input_pin);
+    writePinLow(joystick_axes[axis_index].input_pin);
+    
+#ifdef __AVR__
+    int16_t axis_val = analogReadPin(joystick_axes[axis_index].input_pin);
+#else
+    int16_t axis_val = 0;
+#endif
+    if (axis_val!=joystick_status.axes[axis_index]){
+      joystick_status.axes[axis_index] = axis_val;
+      joystick_status.status |= JS_UPDATED;
+    }
+    
+    writePinLow(joystick_axes[axis_index].output_pin);
+  }
+#endif
+  return true;
+}

quantum/process_keycode/process_joystick.h

@@ -0,0 +1,13 @@
+#ifndef PROCESS_JOYSTICK_H
+#define PROCESS_JOYSTICK_H
+
+#include <stdint.h>
+#include "quantum.h"
+
+bool process_joystick(uint16_t keycode, keyrecord_t *record);
+
+void joystick_task(void);
+
+bool process_joystick_analog(void);
+
+#endif //PROCESS_JOYSTICK_H

quantum/quantum.c

@@ -63,6 +63,10 @@ float bell_song[][2] = SONG(TERMINAL_SOUND);
 #    endif
 #endif
 
+#ifdef JOYSTICK_ENABLE
+#include <process_keycode/process_joystick.h>
+#endif //JOYSTICK_ENABLE
+
 static void do_code16(uint16_t code, void (*f)(uint8_t)) {
     switch (code) {
         case QK_MODS ... QK_MODS_MAX:
@@ -265,6 +269,9 @@ bool process_record_quantum(keyrecord_t *record) {
 #endif
 #if defined(RGBLIGHT_ENABLE) || defined(RGB_MATRIX_ENABLE)
             process_rgb(keycode, record) &&
+#endif
+#ifdef JOYSTICK_ENABLE
+            process_joystick(keycode, record) &&
 #endif
             true)) {
         return false;

quantum/quantum_keycodes.h

@@ -512,6 +512,41 @@ enum quantum_keycodes {
     DYN_MACRO_PLAY1,
     DYN_MACRO_PLAY2,
 
+    JS_BUTTON0,
+    JS_BUTTON_MIN = JS_BUTTON0,
+    JS_BUTTON1,
+    JS_BUTTON2,
+    JS_BUTTON3,
+    JS_BUTTON4,
+    JS_BUTTON5,
+    JS_BUTTON6,
+    JS_BUTTON7,
+    JS_BUTTON8,
+    JS_BUTTON9,
+    JS_BUTTON10,
+    JS_BUTTON11,
+    JS_BUTTON12,
+    JS_BUTTON13,
+    JS_BUTTON14,
+    JS_BUTTON15,
+    JS_BUTTON16,
+    JS_BUTTON17,
+    JS_BUTTON18,
+    JS_BUTTON19,
+    JS_BUTTON20,
+    JS_BUTTON21,
+    JS_BUTTON22,
+    JS_BUTTON23,
+    JS_BUTTON24,
+    JS_BUTTON25,
+    JS_BUTTON26,
+    JS_BUTTON27,
+    JS_BUTTON28,
+    JS_BUTTON29,
+    JS_BUTTON30,
+    JS_BUTTON31,
+    JS_BUTTON_MAX = JS_BUTTON31,
+
     // always leave at the end
     SAFE_RANGE
 };