flix/gazebo/joystick.h

// Copyright (c) 2023 Oleg Kalachev <okalachev@gmail.com>
// Repository: https://github.com/okalachev/flix

// Joystick support for simulation

#include <SDL2/SDL.h>
#include <gazebo/gazebo.hh>
#include <iostream>

// simulation calibration overrides, NOTE: use `cr` command and replace with the actual values
const int channelNeutralOverride[] = {-258, -258, -27349, 0, 0, 1};
const int channelMaxOverride[] = {27090, 27090, 27090, 27090, 0, 1};

#define RC_CHANNEL_ROLL 0
#define RC_CHANNEL_PITCH 1
#define RC_CHANNEL_THROTTLE 2
#define RC_CHANNEL_YAW 3
#define RC_CHANNEL_AUX 4
#define RC_CHANNEL_MODE 5

SDL_Joystick *joystick;
bool joystickInitialized = false, warnShown = false;

void normalizeRC();

void joystickInit() {
	SDL_Init(SDL_INIT_JOYSTICK);
	joystick = SDL_JoystickOpen(0);
	if (joystick != NULL) {
		joystickInitialized = true;
		gzmsg << "Joystick initialized: " << SDL_JoystickNameForIndex(0) << std::endl;
	} else if (!warnShown) {
		gzwarn << "Joystick not found, begin waiting for joystick..." << std::endl;
		warnShown = true;
	}

	// apply calibration overrides
	extern int channelNeutral[RC_CHANNELS];
	extern int channelMax[RC_CHANNELS];
	memcpy(channelNeutral, channelNeutralOverride, sizeof(channelNeutralOverride));
	memcpy(channelMax, channelMaxOverride, sizeof(channelMaxOverride));
}

void joystickGet() {
	if (!joystickInitialized) {
		joystickInit();
		return;
	}

	SDL_JoystickUpdate();

	for (uint8_t i = 0; i < 4; i++) {
		channels[i] = SDL_JoystickGetAxis(joystick, i);
	}
	channels[RC_CHANNEL_MODE] = SDL_JoystickGetButton(joystick, 0) ? 1 : 0;
	controls[RC_CHANNEL_MODE] = channels[RC_CHANNEL_MODE];

	normalizeRC();
}