joystick.h

/* Copyright 2022
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#pragma once

#include <stdbool.h>
#include <stdint.h>

#include "gpio.h"

/**
 * \file
 *
 * \defgroup joystick HID Joystick
 * \{
 */

#ifndef JOYSTICK_BUTTON_COUNT
#    define JOYSTICK_BUTTON_COUNT 8
#elif JOYSTICK_BUTTON_COUNT > 32
#    error Joystick feature only supports up to 32 buttons
#endif

#ifndef JOYSTICK_AXIS_COUNT
#    define JOYSTICK_AXIS_COUNT 2
#elif JOYSTICK_AXIS_COUNT > 6
#    error Joystick feature only supports up to 6 axes
#endif

#if JOYSTICK_AXIS_COUNT == 0 && JOYSTICK_BUTTON_COUNT == 0
#    error Joystick feature requires at least one axis or button
#endif

#ifndef JOYSTICK_AXIS_RESOLUTION
#    define JOYSTICK_AXIS_RESOLUTION 8
#elif JOYSTICK_AXIS_RESOLUTION < 8 || JOYSTICK_AXIS_RESOLUTION > 16
#    error JOYSTICK_AXIS_RESOLUTION must be between 8 and 16
#endif

#define JOYSTICK_MAX_VALUE ((1L << (JOYSTICK_AXIS_RESOLUTION - 1)) - 1)

// configure on input_pin of the joystick_axes array entry to NO_PIN
// to prevent it from being read from the ADC. This allows outputting forged axis value.
#define JOYSTICK_AXIS_VIRTUAL \
    { NO_PIN, 0, JOYSTICK_MAX_VALUE / 2, JOYSTICK_MAX_VALUE }
#define JOYSTICK_AXIS_IN(INPUT_PIN, LOW, REST, HIGH) \
    { INPUT_PIN, LOW, REST, HIGH }

typedef struct {
    pin_t input_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_AXIS_COUNT];

typedef struct {
    uint8_t buttons[(JOYSTICK_BUTTON_COUNT - 1) / 8 + 1];
    int16_t axes[JOYSTICK_AXIS_COUNT];
    bool    dirty;
} joystick_t;

extern joystick_t joystick_state;

/**
 * \brief Handle the initialization of the subsystem.
 */
void joystick_init(void);

/**
 * \brief Handle various subsystem background tasks.
 */
void joystick_task(void);

/**
 * \brief Send the joystick report to the host, if it has been marked as dirty.
 */
void joystick_flush(void);

/**
 * \brief Set the state of a button, and flush the report.
 *
 * \param button The index of the button to press, from 0 to 31.
 */
void register_joystick_button(uint8_t button);

/**
 * \brief Reset the state of a button, and flush the report.
 *
 * \param button The index of the button to release, from 0 to 31.
 */
void unregister_joystick_button(uint8_t button);

/**
 * \brief Sample and process the analog value of the given axis.
 *
 * \param axis The axis to read.
 *
 * \return A signed 16-bit integer, where 0 is the resting or mid point.
 */
int16_t joystick_read_axis(uint8_t axis);

/**
 * \brief Sample and process the all axis.
 */
void joystick_read_axes(void);

/**
 * \brief Set the value of the given axis.
 *
 * \param axis The axis to set the value of.
 * \param value The value to set.
 */
void joystick_set_axis(uint8_t axis, int16_t value);

/** \} */