Add multi-touch basic API (experimental)

teensy3/usb_dev.c

 #endif
 #ifdef FLIGHTSIM_INTERFACE
 			usb_flightsim_flush_callback();
+#endif
+#ifdef MULTITOUCH_INTERFACE
+			usb_touchscreen_update_callback();
 #endif
 		}
 		USB0_ISTAT = USB_ISTAT_SOFTOK;

teensy3/usb_dev.h

 extern unsigned int usb_audio_transmit_callback(void);
 #endif
 
+#ifdef MULTITOUCH_INTERFACE
+extern void usb_touchscreen_update_callback(void);
+#endif
 
 
 #ifdef __cplusplus

teensy3/usb_touch.c

+/* Teensyduino Core Library
+ * http://www.pjrc.com/teensy/
+ * Copyright (c) 2016 PJRC.COM, LLC.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * 1. The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * 2. If the Software is incorporated into a build system that allows
+ * selection among a list of target devices, then similar target
+ * devices manufactured by PJRC.COM must be included in the list of
+ * target devices and selectable in the same manner.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "usb_dev.h"
+#include "usb_touch.h"
+#include "core_pins.h" // for yield()
+#include "HardwareSerial.h"
+#include <string.h> // for memcpy()
+
+#ifdef MULTITOUCH_INTERFACE // defined by usb_dev.h -> usb_desc.h
+#if F_CPU >= 20000000
+
+void usb_touchscreen_press(uint8_t finger, uint32_t x, uint32_t y, uint32_t pressure)
+{
+	// TODO...
+}
+
+void usb_touchscreen_release(uint8_t finger)
+{
+	// TODO...
+}
+
+// Called by the start-of-frame interrupt.
+//
+void usb_touchscreen_update_callback(void)
+{
+	// TODO...
+}
+
+#endif // F_CPU
+#endif // MULTITOUCH_INTERFACE

teensy3/usb_touch.h

+/* Teensyduino Core Library
+ * http://www.pjrc.com/teensy/
+ * Copyright (c) 2013 PJRC.COM, LLC.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * 1. The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * 2. If the Software is incorporated into a build system that allows
+ * selection among a list of target devices, then similar target
+ * devices manufactured by PJRC.COM must be included in the list of
+ * target devices and selectable in the same manner.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+ * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#ifndef USBtouchscreen_h_
+#define USBtouchscreen_h_
+
+#include "usb_desc.h"
+
+#if defined(MULTITOUCH_INTERFACE)
+
+#include <inttypes.h>
+
+// C language implementation
+#ifdef __cplusplus
+extern "C" {
+#endif
+void usb_touchscreen_press(uint8_t finger, uint32_t x, uint32_t y, uint32_t pressure);
+void usb_touchscreen_release(uint8_t finger);
+void usb_touchscreen_update_callback(void);
+#ifdef __cplusplus
+}
+#endif
+
+// C++ interface
+#ifdef __cplusplus
+class usb_touchscreen_class
+{
+        public:
+        void begin(void) { }
+        void end(void) { }
+	void press(uint8_t finger, uint32_t x, uint32_t y, uint32_t pressure=128) {
+		usb_touchscreen_press(finger, x, y, pressure);
+	}
+	void release(uint8_t finger) {
+		usb_touchscreen_release(finger);
+	}
+};
+extern usb_touchscreen_class TouchscreenUSB;
+
+#endif // __cplusplus
+
+#endif // MULTITOUCH_INTERFACE
+
+#endif // USBtouchscreen_h_
+