Optical Flow - added overflow check

libraries/AP_OpticalFlow/AP_OpticalFlow_ADNS3080.cpp

@@ -190,11 +190,14 @@ AP_OpticalFlow_ADNS3080::reset()
 bool
 AP_OpticalFlow_ADNS3080::update()
 {
+    byte motion_reg;
     surface_quality = (unsigned int)read_register(ADNS3080_SQUAL);
 	delayMicroseconds(50);  // small delay
 
     // check for movement, update x,y values
-	if( (read_register(ADNS3080_MOTION) & 0x80) != 0 ) {
+	motion_reg = read_register(ADNS3080_MOTION);
+	_overflow = ((motion_reg & 0x10) != 0);  // check if we've had an overflow
+	if( (motion_reg & 0x80) != 0 ) {
 		raw_dx = ((char)read_register(ADNS3080_DELTA_X));
 		delayMicroseconds(50);  // small delay
 		raw_dy = ((char)read_register(ADNS3080_DELTA_Y));

libraries/AP_OpticalFlow/AP_OpticalFlow_ADNS3080.h

@@ -100,7 +100,8 @@ class AP_OpticalFlow_ADNS3080 : public AP_OpticalFlow
   public:
 	int _cs_pin;     // pin used for chip select
 	int _reset_pin;  // pin used for chip reset
-	bool _motion;  	// true if there has been motion
+	bool _motion;  	 // true if there has been motion
+	bool _overflow;  // true if the x or y data buffers overflowed
 
   public:
   	AP_OpticalFlow_ADNS3080(int cs_pin = ADNS3080_CHIP_SELECT, int reset_pin = ADNS3080_RESET);

libraries/AP_OpticalFlow/examples/AP_OpticalFlow_test/AP_OpticalFlow_test.pde

@@ -312,6 +312,10 @@ void display_motion()
 	    flowSensor.update();
 		flowSensor.update_position(0,0,0,1,100);
 
+		// check for errors
+		if( flowSensor._overflow )
+		    Serial.println("overflow!!");
+
 		// x,y,squal
 		//if( flowSensor.motion() || first_time ) {
 			Serial.print("x/dx: ");