2

Use-case

  • Implement a HID "Touch Screen" for a SmartPhone device using USB
  • "Touch Screen" should operate well in either landscape or portrait orientation

Dev Environment

  • Samsung Galaxy 5
  • Android 5

Problem description

When the phone is in the Portrait orientation ( 1080x1920 ) all is perfectly working, when changing to landscape orientation ( 1920x1080 ) coordinates are 90 degrees rotated and movement along the X axes ( now 1920 ) is limited to 1080.

Manually switching the X & Y coordinates sent through the HID Report makes the cursor aligned with the physical movement of the device, however the horizontal axes ( now 1920 ) is still limited to 1080.

On the HID Descriptor, Making the LOGICAL_MAXIMUM lager than the PHYSICAL_MAXIMUM didn't have any affect...

Is it possible, at-all, to support orientation changes for a Digitizer device ? should I change the descriptor in any way to have the orientation changes properly work ?

UPDATE

  • Using USAGE_PAGE Digitizers (0x0D) w/ Azimuth USAGE_ID (0x3F) didn't have any affect
  • Using USAGE_PAGE 'Alpha Numeric Display (0x14)' w/ 'Display Orientation' USAGE_ID (0x84) didn't have any affect

Code Snippet ( Implemented according to this link )

            enum :BYTE { REPORT_ID = 4 };

            const UCHAR DESCRIPTOR[] = {
                0x05, 0x0d,                         // USAGE_PAGE (Digitizers)
                0x09, 0x04,                         // USAGE (Touch Screen)
                0xa1, 0x01,                         // COLLECTION (Application)
                0x85, REPORT_ID,                    //   REPORT_ID (4)
                0x09, 0x20,                         //   USAGE (Stylus)
                0xa1, 0x00,                         //   COLLECTION (Physical)
                0x09, 0x42,                         //     USAGE (Tip Switch)
                0x09, 0x32,                         //     USAGE (In Range)
                0x15, 0x00,                         //     LOGICAL_MINIMUM (0)
                0x25, 0x01,                         //     LOGICAL_MAXIMUM (1)
                0x75, 0x01,                         //     REPORT_SIZE (1)
                0x95, 0x02,                         //     REPORT_COUNT (2)
                0x81, 0x02,                         //     INPUT (Data,Var,Abs)
                0x75, 0x01,                         //     REPORT_SIZE (1)
                0x95, 0x06,                         //     REPORT_COUNT (6)
                0x81, 0x01,                         //     INPUT (Cnst,Ary,Abs)
                0x05, 0x01,                         //     USAGE_PAGE (Generic Desktop)
                0x46, 0x10, 0x27,                   //     PHYSICAL_MAXIMUM (10000)
                0x26, 0x10, 0x27,                   //     LOGICAL_MAXIMUM (10000)
                0x75, 0x10,                         //     REPORT_SIZE (16) 
                0x95, 0x01,                         //     REPORT_COUNT (1)            
                0x55, 0x0F,                         //     UNIT_EXPONENT (-1)           
                0x65, 0x11,                         //     UNIT (cm,SI Linear)                  
                0x35, 0x00,                         //     PHYSICAL_MINIMUM (0)         
                0x45, 0x00,                         //     PHYSICAL_MAXIMUM (0)
                0x09, 0x30,                         //     USAGE (X)                    
                0x81, 0x02,                         //     INPUT (Data,Var,Abs)         
                0x09, 0x31,                         //     USAGE (Y)                    
                0x81, 0x02,                         //     INPUT (Data,Var,Abs)
                0xc0,                               //   END_COLLECTION
                0xc0,                               // END_COLLECTION
            };

            struct Report {
                enum :LONG { RES_X = 10000, RES_Y = 10000 };
                UCHAR   report_id; // Must be set to 4
                struct {
                    UCHAR   bTipSwitch : 1;
                    UCHAR   bInRange   : 1;
                    UCHAR   reserved   : 6;
                } status;
                USHORT  wXData;
                USHORT  wYData;

                inline static void NormalizeCoordinates(IN const SIZE& res, IN OUT USHORT& x, IN OUT USHORT& y) {
                    if ((0 == res.cx) || (0 == res.cy)) {
                        assert(FALSE);
                        return;
                    }
                    x = (USHORT)((RES_X * x) / res.cx);
                    y = (USHORT)((RES_Y * y) / res.cy);
                }
            };
NadavRub
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  • Generally: The HID device sends coordinates between 0 and a maximum value. Then the operating system translates these values into the real coordinates of the screen. So you may always send 0....10000 for X and Y and it should work like that even if rotation takes place or even if the screen resolution changes. If it does not work, this is a bug in the operating system. (Why do you set Physical Maximum first 10000 and then 0 ? This is surely not the cause of the problem, but makes no sense. You should declare Physical + Logical Minimum + Maximum for X and Y) – Elmue Feb 17 '16 at 17:06

0 Answers0