3M Touch Systems

Mark RobertsField Application Engineer

August 14, 2002

Touchscreen Integration and Troubleshooting

3M Touch Systems

Capacitive Touchscreen

• Glass panel

• ClearTek Overcoat

• Etch or Polish

• Touch Coatings

• Electrodes

Construction

ClearTekOvercoat

ConductiveTouchCoating

GlassPanel

Etch or PolishRearShieldCoating

Electrodes

3M Touch Systems

Capacitive Technology

How it works!

A controller A controller calculates the calculates the position of the position of the finger from the finger from the current flowscurrent flows

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Voltage is applied to Voltage is applied to four corners of the screenfour corners of the screen

Electrodes spread out Electrodes spread out voltage creating a voltage creating a uniform voltage fielduniform voltage field

The touch of a finger The touch of a finger draws current from draws current from each side in proportion each side in proportion to the distance from to the distance from the edgethe edge

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22

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3M Touch Systems

Capacitive Technology

V o lta g e is a p p lie d to 4 c o rn e rs .

S p e c ia l e le c tro d e s l in e a r iz eth e v o lta g e f ie ld

C u rre n t f lo w fro m 4 c o rn e rs is m e a s u re da n d p o s it io n is c a lc u la te d

3M Touch Systems

Capacitive Controller Technology

• Power• Orange - +12v, 60ma max, 47 ma typical, 400 mv

max ripple• Gray - Power Supply Ground• Green - Chassis Ground, as short as possible

Important: Electrostatic Discharge “ESD” path!!• Gray/Green - Can be combined to Chassis Ground• Touch working

– Tap the Touchscreen, LED should flash

3M Touch Systems

Capacitive Controller Technology

Communications with System

– Power on system, should find the controller

(LED will go from “bright” to “dim” on power up)

– If not, turn power off

– unplug the Touchscreen

– power back up

3M Touch Systems

Materials and Tools• Recommended Materials

– Double Sided Tape (Touchscreen - display)• 3M 4416 (1/16” thick) 8 pieces (1.5” long)• 3M 4408 (1/8” thick) 8 pieces (1.5”long)

– Closed cell single sided Gasket (bezel - Touchscreen)• Volara 2AF• Epilon FR

– Cloth Tape• Ideal Brand Therm-X No. 724

• Tools– Isopropyl Alcohol– Lint free cloth– X-acto Knife

3M Touch Systems

Removing the Touchscreen

• Peel away gap tape• Use X-acto knife to

cut foam tape from top, left, right sides from the outside edge

• Lean Touchscreen forward & cut bottom tape from between Touchscreen and Display.

3M Touch Systems

Preparing Display & Touchscreen

• Use Isopropyl Alcohol and soft lint free cloth

• Clean the surface of the Display

• Clean the inside surface of the Touchscreen

3M Touch Systems

Alignment of the Touchscreen

• Align the Touchscreen

• both horizontally and

• vertically with the

• tube/LCD

3M Touch Systems

Cover the air gap

• Use the Black Cloth tape

• Cover the perimeter of the Touchscreen fully covering the space between the Touchscreen and Display

3M Touch Systems

Preparing Power for the Controller

• Orange - +12v, 60ma max, 47 ma typ, 400 mv max ripple

• Gray - Power Supply Ground

• Green - Chassis Ground, as short as possible

• Gray/Green - Can be combined to Chassis Ground

3M Touch Systems

Trouble Shooting Tips

• Touch Working ?

LED should go from “dim” to “bright” when the sensor is touched. If yes, touch is working, problem is downstream from controller

• No Response from LED or touch ?

- Is there power to the controller/Touchscreen ?

- Is there any wires broken on the touchscreen ?

- Is the touchscreen 12pin header plugged into the controller ?

- Is the controller serial cable connected to the correct port ?

3M Touch Systems

Trouble Shooting Tips

• Definitions:- Serial

Serial is a very common protocol for device communication that is standard on almost every PC. The concept of serial communication is simple. The serial port sends and receives bytes of information one bit at a time. Communication is completed using 3 transmission lines: (1) Ground, (2) Transmit, and (3) Receive. Other lines are available for handshaking, but are not required. The important serial characteristics are baud rate, data bits, stop bits, and parity. For two ports to communicate, these parameters must match!

3M Touch Systems

Trouble Shooting Tips• Definitions Cont. :- Baud Rate

Baud rate is the speed measurement for communication on a serial line. It indicates the number of bit transfers per second. Common baud rates for touch controllers are: 1200, 2400, 4800, and 9600.

- Parity

Parity is a simple form of error checking that is used in serial communication. Odd, Even, or No Parity is available on the controller. For even and odd parity, the serial port sets the parity bit (the last bit after the data bits) to a value to ensure that the transmission has an even or odd number of logic high bits. Example is parameter setting N72. The “N” = there is no parity.

3M Touch Systems

Trouble Shooting Tips

• Definitions Cont. :

- Stop Bits

Stop bits: used to signal the end of communication for each data byte. Possible values are 1 and 2 bits for the 3MTS controller.

3M Touch Systems

Trouble Shooting Tips

• Controller Configuration ? - Parameter Settings ARE important:Sample: Controller Setting “N72, 9600”“N”=Parity, “7”= data bits, “2”= Stop bits, “9600” = Baud Example: N81, 9600 baud = Host Communication Setting N72, 9600 baud = Controller (default) Setting Going by the above, the system Host will never find the controller at power

up. They are on different communication settings, thus do not see each other. Similar to two people speaking the wrong language to each other…. They will not understand what each other is communicating.

- Use the “MicroCal” Dos Utility to change the controller Parameter settings.

3M Touch Systems

Trouble Shooting Tips

• Touch is “Jittery” ?

- Noise in the system is interfering with the controller and

prevents it from receiving a clear signal. To correct

this a controller “Frequency Adjustment” Utility is available in

the 3MTS MicroCal software utility.

Note: The newly released EX II controller handles “Frequency

Adjustments” internally, thus correcting Jitter problems

automatically.

3M Touch Systems

Trouble Shooting Tips

• Calibration:

- Target / finger positioning: Touchscreen calibration is only as good as the manner in which it was calibrated.

Improper calibration will result in positional offsets on the touchscreen. Touch the targets straight on, do not use a swiping motion.

- Important to take note of “Instructions” on Game Systems: Gaming companies treat calibration in different ways on their machines. There is sub

routines going on behind the screen during calibration, caution must be taken to follow exact instructions on the screen. Example: If the screen displays “Open door, taking ambient, do not touch screen” it is critical that the instruction is followed. The door must be completely open with no obstructions between the door and touchscreen. Is is also important to assure your hands are away from the touchscreen during this time. The touchscreen is taking an ambient measurement of the environment. If this measurement is taken incorrectly, a positional offset will be the result on the touchscreen.

3M Touch Systems

Questions?