DDHidLib - Implementing a joystick (Logitech 3D Extreme PRO) - objective-c

Question

I have recently decided to start a project which requires some kind of direct input to control my application and, in my case, I decided to use my Logitech 3D Extreme PRO joystick.
Therefore I started documenting myself online using the HID Class Device Interface Guide provided by Apple (Even the one dealing with the new HID Manager for OS X 10.5). I was able to implement the very main methods but unfortunately none of them worked.
After few days of search I have discovered a great Library developed by Daij-Djan : DDHidLib which helps a lot when dealing with direct inputs, providing great methods for discovering button presses and stick toggles, queues and lot more.
Even though this lib is a bit odd (2007), I decided to import it and give it a try..
I imported it into my project and started implementing some of it's methods which apparently seem very easy.
For instance, inside the DDHidJoystick sub-class, I found:
- (void)ddhidJoystick:(DDHidJoystick *)joystick buttonDown:(unsigned)buttonNumber
This method returns the number of the button that have been pressed.
Now, after this long introduction, let me explain my problem:
I coded a tested implementation of this class but without success (At least with my hardware).
Apparently with no reason the method reported above gets called only if I press one button on my joystick (Number 7).
Therefore I get some kind of notification {NSLog()} just in that case, even though the library is deigned to retrive any kind of input from the device.
But the most weird thing is that I am able to retrive all the other buttons/povs/sticks values only by pressing that specific button (N. 7) at the same time.
So let's say I want to get input from button 8, I will have to press button 8, than, at the same time, button number 7. Now i got a notification for both inputs.
If I want to get x-axis value, I need to:
Move x-stick
Press button n. 7
Then I see one notification both for button n.7 and x-axis moved at the same time.
To clarify, let me introduce this method:
- (void)ddhidJoystick:(DDHidJoystick *)joystick
stick:(unsigned)stick
xChanged:(int)value
As you can imagine, this method should be triggered whenever I move my X-Axis stick, however it doesn't.
Instead it gets triggered only if I press button number 7 and then, at the same time,I move my stick !
I tested out the joystick with X-Plane 10 and works just fine, so my guess is that there should be something else different from my app acquiring the input and hiding it.
I'm expecting to move my axis-sticks and se a NSLog, but that is not happening.
I'm not requesting a specific response on how to achieve my task using this lib, any other working approach will really be appreciated.
I really hope that this question is not too specific and could be helpful to somebody else in the future since nobody (apparently) tried to implement such input.
Thanks a lot to anyone who will reply to this post.
For the most curious:
I am building my own quad-copter using Arduino/Raspberry and lot of other electronics. I got a TX/RX Module operating at 2.4GHz which allows communication between 2 boards: one on the quad, and the other one plugged to the pc. I developed a lib (in C) reading POSIX documentation to read/write to serial ports and therefore I am able to send data over usb to my board, which than sends it to the quad. Finally I'am developing an OS X app to control the copter using the mentioned hardware/software and it is not far from being finished.
However for my purposes I want to use my joystick, and this is difficult.
In the end I will have a live video from onboard (FPV-Like) on the screen with telemetry all controlled by my Logitech 3D Extreme.
EDIT - I FOUND A SOLUTION
I found a solution and it seems to work pretty good!
Basically I had to edit a bit one method of the lib, adding support for the engine slider the joystick has.
Open up DDHidJoystick.m
Locate the method - (BOOL) addElement: (DDHidElement *) element;
Add the case statement case kHIDUsage_GD_Slider:
Set the action to [mStickElements addObject: element];
I will post the code here just in case somebody needs it in the future:
- (BOOL) addElement: (DDHidElement *) element;
{
DDHidUsage * usage = [element usage];
if ([usage usagePage] != kHIDPage_GenericDesktop)
return NO;
BOOL elementAdded = YES;
switch ([usage usageId])
{
case kHIDUsage_GD_X:
if (mXAxisElement == nil)
mXAxisElement = [element retain];
else
[mStickElements addObject: element];
break;
case kHIDUsage_GD_Y:
if (mYAxisElement == nil)
mYAxisElement = [element retain];
else
[mStickElements addObject: element];
break;
case kHIDUsage_GD_Z:
case kHIDUsage_GD_Rx:
case kHIDUsage_GD_Ry:
case kHIDUsage_GD_Rz:
[mStickElements addObject: element];
break;
case kHIDUsage_GD_Hatswitch:
[mPovElements addObject: element];
break;
/* EDIT HERE */
case kHIDUsage_GD_Slider:
[mStickElements addObject: element];
default:
elementAdded = NO;
}
return elementAdded;
}
Under this line you can find my whole implementation, and an image of the joystick.
(Developing on OS X 10.10 - Alberto Bellini)
#implementation AppDelegate
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
// Insert code here to initialize your application
[self startWatchingJoysticks];
}
- (void)applicationWillTerminate:(NSNotification *)aNotification {
// Insert code here to tear down your application
}
- (void)startWatchingJoysticks
{
//get an array of all joystick objects
joySticks = [[DDHidJoystick allJoysticks] retain];
//become the delegate of all available joystick objects
[joySticks makeObjectsPerformSelector:#selector(setDelegate:) withObject:self];
[joySticks makeObjectsPerformSelector:#selector(startListening) withObject:nil];
}
- (void)dealloc
{
[joySticks release];
[super dealloc];
}
//these are the DDHidLib joystick delegate methods related to buttons
- (void)ddhidJoystick:(DDHidJoystick *)joystick buttonDown:(unsigned)buttonNumber
{
NSLog(#"button down: %d", buttonNumber);
//Works only number 7
}
- (void)ddhidJoystick:(DDHidJoystick *)joystick
stick:(unsigned)stick
xChanged:(int)value
{
NSLog(#"x axis %d",value);
//Works ONCE only if presing button number 7 and moving stick
}
- (void)ddhidJoystick:(DDHidJoystick *)joystick
stick:(unsigned)stick
yChanged:(int)value
{
NSLog(#"y axis %d",value);
//Works ONCE only if presing button number 7 and moving stick
}
- (void)ddhidJoystick:(DDHidJoystick *)joystick
stick:(unsigned)stick
otherAxis:(unsigned)otherAxis
valueChanged:(int)value
{
NSLog(#"z axis %d",value);
//Works ONCE only if presing button number 7 and moving stick
}
- (void)ddhidJoystick:(DDHidJoystick *)joystick
stick:(unsigned)stick
povNumber:(unsigned)povNumber
valueChanged:(int)value
{
NSLog(#"Pov changed");
//Works ONCE only if presing button number 7 and moving stick
}
#end

Answer 1

Maybe I found the problem with your joystick.
Logitech Extreme 3D has no standard data packet for joysticks. It has different HID report descriptor and I can not found HID report descriptor parser in DDHidLib. I think DDHidLib just assume standard data packet.
Check this link: http://www.circuitsathome.com/mcu/using-logitech-extreme-3d-pro-joystick-with-arduino-hid-library
Unfortunately, I can not help you more because I don't know nothing about objetive-c nor OSX nor HID.
Maybe you can modify data packet structure in DDHidLib, create a HID report descriptor parser for DDHidLib or get a new joystick with standard data packet. ;)