Clever Pointer Device Samer Aamar Post PC Course

Clever Pointer Device Samer Aamar Post PC Course – 2002 1

It would be great to be able to… w move next/previous without the need to be near your PC/Laptop w mark important words / draw basic shapes (circles, arrows, etc. ) with his pointer device w press on buttons on the screen, activate shortcuts, surf in WEB… 2

Well, sounds like a Mouse! 3

How does it work? w The pointing device will plot a virtual ray! w The intersection with the projection screen will be calculated (3 D space) w The computer will translate the intersection 3 D point into a 2 D point on the screen. w Mouse Move events will be fired to the system 4

h yy hh y x w ww xx y/yy = h/hh x/xx=w/ww 5

Some mathematics p 1 p 2 w The points p 1, p 2 are in 3 D space w The ray vector p 2 -p 1 w It would be easy to calculate the intersection point with the screen BUT, before all the coordinates of the projection screen should be defined 6

Components Basic components: Transmitter buttons w 2 Tri-Axis Accelerometers w Three buttons 3 D Accelerometers w Transmitter/Receiver (wireless) 7

Buttons The device has three buttons: w ‘Activate’ button: When down the MOUSE_MOVE event is fired w ‘LButton’ / ‘RButton’ button: n samples the Left/Right Button on the regular mouse 8

Press On Activate 9

Press On Activate 10

Hold Activate and Move Pointer! 11

Release Activate button! 12

Release Activate button! Press on LButton/RButton 13

Accelerometers We need: n 3 -Axis Accelerometer n MEMS (Micro Electro Mechanical Systems) Acc. : Small l Light l n Ability to measure hand motion (next slide) 14

Measuring Hand Motion Parameter Target Value Frequency Range 0. 1 to 25 Hz Acceleration Amplitude +/- 5 g Acceleration Resolution 1 mg g ~ 9. 8 m/sec 2 15

Accelerometers (II) Good enough (according to the sheets) w Analog Device i. MEMS accelerometers n n ADXL 105 ADXL 150 w Microsystems Technology Laboratory (MTL) w 3 -Axis accelerometers: n n TG Series Accelerometers: CXL 10 TG 3 (crossbow tech. ) ACCELEROMETERS by Vernier 16

Analog Devices Performance Resolution of ADI accelerometer sensors over time Cost of performance in ADI accelerometer sensors over time 17

Relevant Thesis w Graham B. ; Using an Accelerometer Sensor to Measure Human Hand Motion; Massachusetts Institute of Technology; 2000. w He achieved the following: n n Frequency: Amplitude: Mass: Size: 0. 1 – 25 Hz ± 10 g 4. 88 grams (17 mm)^3 18

Transmitter/Receiver w Frequency: 25 Hz w Data (bits): n n 2 x 32 (X, Y, Z) 3 (buttons) w Total (per second) 25 x 194 = 4850 = 4. 8 Kb per sec w Possibilities Bluetooth – too much! Radio transmitter/receiver – simple: 10 Kb per sec is OK! 19

Summary Required Existing 3 -Axis Accelerometers Three single-axis accelerometers (Analog Devices) Receiver/Transmitter Radio 20

Open Issues! w CPU Consuming? w Sudden movements – like sharply putting the device on the table (20 g) w What happens if the connection between transmitter and receiver was interrupted temporarily for some reason (example by moving to another room) 21

Related Sites w http: //www. analog. com w http: //shop. store. yahoo. com/crossbow/index. html w http: //www-mtl. mit. edu/MEng. TP/Graham_Thesis. pdf 22

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