 | | | HID manager - is it worth it? | HID manager - is it worth it? 2004-12-11 - By George Warner
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On Thu, 9 Dec 2004 15:42:19 -0500, Tim Conkling <tconkling@(protected)> wrote:
> I have zero experience with the HID manager and I'm interested in
> hearing game developers' experiences and opinions on using it.
Everything you need for input is in the HID Utilities sample source code at:
<http://developer.apple.com/samplecode/Sample_Code/Devices_and_Hardware/HID_
Manager/HID_Utilities_Source.htm>.
1) Download the HID Utilities sample code.
2) Double-click the HID Utilities slib.pbproj file to open it in
Project Builder (or xcode).
3) Click build. This will create a build folder that will contain
libHIDUtilities.a once it's finished building.
4) Copy and add libHIDUtilities.a to your project.
5) Add "#include "HID_Utilities_External.h"" and
"#include <Kernel/IOKit/hidsystem/IOHIDUsageTables.h>"
to your game device code file(s).
The "interesting" API's are:
HIDBuildDeviceList - This creates a list of all the HID devices.
HIDReleaseDeviceList - call this when you're done with the list.
HIDGetFirst/NextDevice - used to iterate the devices
HIDGetFirst/NextDeviceElement - used to iterate elements of a device.
HIDGetElementNameFromVendorProduct[Cookie|Usage] - Get text name of an
element.
HIDQueueDevice - Add all device elements to event queue
HIDDequeueDevice - remove device from event queue
HIDQueueElement - Add element to event queue
HIDDequeueElement - remove element from event queue
HIDGetEvent - poll queue for events
6) Build a list of devices by doing:
HIDBuildDeviceList( NULL, NULL );
if (! HIDHaveDeviceList() )
return NULL;
num_devices = HIDCountDevices();
7) Loop through the devices, looking for the one(s) you're interested in.
You find it by matching its usage and usagePage. For example, for a
game pad, you'd look for a usagePage of kHIDPage_GenericDesktop and a
usage of kHIDUsage_GD_GamePad. (All this stuff is found in
IOHIDUsageTables.h)
pRecDevice deviceCandidate = NULL, *stored_device[100];
int i, foundDevices = 0;
deviceCandidate = HIDGetFirstDevice();
i = 0;
while ( i < num_devices ) {
if ( deviceCandidate ) {
//here I filter out keyboards, mice and totally unrelated devices
if ( (deviceCandidate->usage == kHIDUsage_GD_Keyboard)
|| (deviceCandidate->usagePage != kHIDPage_GenericDesktop) ||
(deviceCandidate->usage == kHIDUsage_GD_Mouse) ) {
if ( HIDIsValidDevice( deviceCandidate ) ) {
//skip this one and just go on to the next one
deviceCandidate = HIDGetNextDevice( deviceCandidate );
} else {
//handle error
}
} else {
if ( HIDIsValidDevice( deviceCandidate ) ) {
//store the device in a list of devices we're interested in
stored_device[foundDevices] = deviceCandidate;
deviceCandidate = HIDGetNextDevice( deviceCandidate );
foundDevices++;
} else {
//handle error
}
}
}
i++;
}
8) Now that you've got the device, go through its elements and find
the axis or button you're interested in:
if ( HIDIsValidDevice( device ) ) {
elRec = HIDGetFirstDeviceElement( js_devices[id].device,
kHIDElementTypeInput );
if ( elRec ) {
switch (elRec->usagePage) {
case kHIDPage_GenericDesktop:
switch ( elRec->usage ) {
case kHIDUsage_GD_X:
x_axis = elRec;
break;
case kHIDUsage_GD_Y:
y_axis = elRec;
break;
case kHIDUsage_GD_GamePad:
pad = elRec;
break;
//etc
}
}
//if the right element was not found, continue looping through the
//rest of the elements by calling HIDGetNextDeviceElement() until you
//find the right one or it returns NULL
}
9) Now that you've got the actual element, you can query it's value:
if ( HIDIsValidElement( devicePtr, elementPtr ) ) {
value = HIDGetElementValue(devicePtr, elementPtr);
}
10) Or add it to a queue:
if ( HIDIsValidElement( devicePtr, elementPtr ) ) {
HIDQueueElement (devicePtr, elementPtr);
}
11) that you can check by:
while (HIDGetEvent(&tDevice, tHIDEvent)) {
// process tHIDEvent
}
You may incorporate the entire HID Utilities into your project as-is or cut
& paste the pieces that you need.
--
Enjoy,
George Warner,
Schizophrenic Optimization Scientist
Apple Developer Technical Support (DTS)
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