I am implementing a USB touchscreen interface that should work on Android.
From https://github.com/denilsonsa/atmega8-magnetometer-usb-mouse/blob/master/firmware/main.c#L159 First I tried:
// Mouse 0x05, 0x01, // USAGE_PAGE (Generic Desktop) 0x09, 0x02, // USAGE (Mouse) 0xa1, 0x01, // COLLECTION (Application) 0x85, 0x02, // REPORT_ID (2) 0x09, 0x01, // USAGE (Pointer) 0xa1, 0x00, // COLLECTION (Physical) // X, Y movement 0x09, 0x30, // USAGE (X) 0x09, 0x31, // USAGE (Y) 0x26, 0xff, 0x7f, // LOGICAL_MAXIMUM (32767) 0x75, 0x10, // REPORT_SIZE (16) 0x95, 0x02, // REPORT_COUNT (2) 0x81, 0x42, // INPUT (Data,Var,Abs,Null) 0xc0, // END_COLLECTION // Buttons 0x05, 0x09, // USAGE_PAGE (Button) 0x19, 0x01, // USAGE_MINIMUM (Button 1) 0x29, 0x03, // USAGE_MAXIMUM (Button 3) 0x25, 0x01, // LOGICAL_MAXIMUM (1) 0x75, 0x01, // REPORT_SIZE (1) 0x95, 0x03, // REPORT_COUNT (3) 0x81, 0x02, // INPUT (Data,Var,Abs) // Padding for the buttons 0x95, 0x05, // REPORT_COUNT (5) 0x81, 0x03, // INPUT (Cnst,Var,Abs) 0xc0 // END_COLLECTION
This worked correctly on Ubuntu 16.04, but did nothing on Android 6.
Then from https://www.codeproject.com/Articles/1001891/A-USB-HID-Keyboard-Mouse-Touchscreen-emulator-with "First Alternative Touch Screen Descriptor" I tried:
0x05, 0x0d, // USAGE_PAGE (Digitizer) 0x09, 0x02, // USAGE (Pen) 0xa1, 0x01, // COLLECTION (Application) // declare a finger collection 0x09, 0x20, // Usage (Stylus) 0xA1, 0x00, // Collection (Physical) // Declare a finger touch (finger up/down) 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) // Declare the remaining 6 bits of the first data byte as constant -> the driver will ignore them 0x75, 0x01, // REPORT_SIZE (1) 0x95, 0x06, // REPORT_COUNT (6) 0x81, 0x01, // INPUT (Cnst,Ary,Abs) // Define absolute X and Y coordinates of 16 bit each (percent values multiplied with 100) // http://www.usb.org/developers/hidpage/Hut1_12v2.pdf // Chapter 16.2 says: "In the Stylus collection a Pointer physical collection will contain the axes reported by the stylus." 0x05, 0x01, // Usage Page (Generic Desktop) 0x09, 0x01, // Usage (Pointer) 0xA1, 0x00, // Collection (Physical) 0x09, 0x30, // Usage (X) 0x09, 0x31, // Usage (Y) 0x16, 0x00, 0x00, // Logical Minimum (0) 0x26, 0x10, 0x27, // Logical Maximum (10000) 0x36, 0x00, 0x00, // Physical Minimum (0) 0x46, 0x10, 0x27, // Physical Maximum (10000) 0x66, 0x00, 0x00, // UNIT (None) 0x75, 0x10, // Report Size (16), 0x95, 0x02, // Report Count (2), 0x81, 0x02, // Input (Data,Var,Abs) 0xc0, // END_COLLECTION 0xc0, // END_COLLECTION 0xc0 // END_COLLECTION // With this declaration a data packet must be sent as: // byte 1 -> "touch" state (bit 0 = pen up/down, bit 1 = In Range) // byte 2,3 -> absolute X coordinate (0...10000) // byte 4,5 -> absolute Y coordinate (0...10000)
What worked on Android, with a little click of the mouse cursor appearing whenever the screen was touched.
What is the correct usbHidReportDescriptor for Android?
Update:
The current behavior is observed when sending "3" for the buttons, that is, "Pen Down" and "In Range".
If I send "2": "In range" I get just without clicking the mouse.
If I send "1": "Pen Down", I get a non-absolute circular cursor.