Added Contact Count to Teensy3 multi touch report

teensy3/usb_desc.c

         0x95, 0x01,                     //   Report Count (1)
         0x09, 0x56,                     //   Usage (Scan Time)
         0x81, 0x02,                     //   Input (variable,absolute)
+        0x09, 0x54,                     //   USAGE (Contact count)
+        0x25, 0x7f,                     //   LOGICAL_MAXIMUM (127) 
+        0x95, 0x01,                     //   REPORT_COUNT (1)
+        0x75, 0x08,                     //   REPORT_SIZE (8)    
+        0x81, 0x02,                     //   INPUT (Data,Var,Abs)
         0x05, 0x0D,                     //   Usage Page (Digitizers)
         0x09, 0x55,                     //   Usage (Contact Count Maximum)
         0x25, MULTITOUCH_FINGERS,       //   Logical Maximum (10)

teensy3/usb_desc.h

   #define KEYMEDIA_INTERVAL     4
   #define MULTITOUCH_INTERFACE  3	// Touchscreen
   #define MULTITOUCH_ENDPOINT   5
-  #define MULTITOUCH_SIZE       8
+  #define MULTITOUCH_SIZE       16
   #define MULTITOUCH_FINGERS    10
   #define ENDPOINT1_CONFIG	ENDPOINT_TRANSMIT_ONLY
   #define ENDPOINT2_CONFIG	ENDPOINT_RECEIVE_ONLY
   #define MOUSE_INTERVAL        2
   #define MULTITOUCH_INTERFACE  4	// Touchscreen
   #define MULTITOUCH_ENDPOINT   5
-  #define MULTITOUCH_SIZE       8
+  #define MULTITOUCH_SIZE       16
   #define MULTITOUCH_FINGERS    10
   #define ENDPOINT1_CONFIG	ENDPOINT_TRANSMIT_ONLY
   #define ENDPOINT2_CONFIG	ENDPOINT_RECEIVE_ONLY

teensy3/usb_touch.c

 //  5: Y msb
 //  6: scan time lsb
 //  7: scan time msb
-
+//	8: contact count
 
 // Called by the start-of-frame interrupt.
 //
 void usb_touchscreen_update_callback(void)
 {
+	uint8_t contact_count = 0;
+
 	if (scan_index == 0) {
 		if (usb_tx_packet_count(MULTITOUCH_ENDPOINT) > 1) {
 			// wait to begin another scan if if more than
 		}
 		scan_timestamp = millis() * 10;
 		scan_count = 0;
+
+		// Get the contact count (usage 0x54)
+		// Only set this value on first contact
+		// Subsequent concurrent contacts should report 0
+		for (uint8_t i = 0; i < MULTITOUCH_FINGERS; i++)
+		{
+			if (contactid[i]) contact_count++;
+		}
 	}
+
 	while (scan_index < MULTITOUCH_FINGERS) {
 		uint32_t press = pressure[scan_index];
 		uint32_t id = contactid[scan_index];
 			*(tx_packet->buf + 5) = ypos[scan_index] >> 8;
 			*(tx_packet->buf + 6) = scan_timestamp;
 			*(tx_packet->buf + 7) = scan_timestamp >> 8;
-			tx_packet->len = 8;
+			*(tx_packet->buf + 8) = contact_count;
+			tx_packet->len = 9;
 			usb_tx(MULTITOUCH_ENDPOINT, tx_packet);
 			scan_index++;
 			return;