Session 5-Maximizing Hardware & Software ... - touchscreens

mammettiredΜηχανική

18 Νοε 2013 (πριν από 3 χρόνια και 6 μήνες)

74 εμφανίσεις

Michael Woolstrum

CEO
,
Touch International


What hardware issues do I need to be aware of prior to
designing a touch screen device?


How
do my hardware choices affect software
development and system performance
?


Topics
Covered:


Touch Product Design Considerations


Touch Technology Issues


Designing for High
-
Performance


Touch Screen Tail Design


Choosing the Right Interface


Touch Screen Electronics


Tuning, Firmware & Calibration






When designing a unit, consider:



Size of display and overall system size


How you want touch screen to look and function


Application


Time to market


Environment


Industry regulations


Cost





Key LCD Considerations


LCD lifespan is short


3 years is common


No standard dimensions


7” is most standard size


Select narrower
borders for flush finish


Design bezel and touch screen for LCD changes


Does application require high
-
bright, high/low temp, high
light
transmission, or sealable LCD?


Is
LCD

easily
acquired?


Cost




Determine Touch Technology


Things to consider:


Application


Environment


Availability


Cost


Also consider


Difficulty to manufacture (complexity)


Touch
i
nput method (finger, pen, glove)


How long does touch screen need to last?






Projected Capacitive for iPhone Experience


Custom designs often very complex


Higher
cost compared to
resistive


False touches possible


Tuning required


Prone
to noise interference


may require EMI
shielding


Multiple input methods dependent upon tuning


Sensitive
to water


Integration can be complex




Typical Projected Capacitive Touch Screen Integration







Add back housing to graphic

Resistive for Low Cost


Moving parts make resistive not as durable


Cover
glass is not typically an option


Requires input pressure


Periodic recalibration


Lower optics


Requires bezel around touch screen


Not the “look” that many expect today




Optical for Large Format


Occlusion (line of sight) problems when light path is blocked


Subject to interference from other light sources or reflections


Thicker bezel needed to hide IR cameras
(3mm for 19” screen)


Possibility
of false
touches


Susceptible to ghosting









Meeting Industry Regulations with Display Enhancements


Adding display enhancements to touch can correct many
environmental and regulatory issues.


Military, Medical, Aerospace Industries


many requirements


Aerospace


HIC Compliant, Self Extinguishing, Low Toxicity


Military
-

NVIS compliant, EMI shielding, high
-
temperature tolerant


Medical
-

NEMA sealable, anti
-
microbial, shatterproof

Military Application Requirements


Extreme Outdoor Environments


Advanced Sunlight Readability


Optimized Video & Light Images


NVIS (Night Vision Imaging System) Compliant



Key component to getting touch screen
right


Consider
how much room tail has and placement of it


Bending tail
can damage communication



Chip
-
on
-
Flex


Only available for projected capacitive


Allows for tail to be
long and far away from
electronics


Minimizes
noise and interference


Entire sensor scrapped if chip needs to be replaced


Chip
-
on
-
flex is expensive



I2C


USB




Projected capacitive accepts
any interface method


Resistive
requires USB
or RS232


Optical usually USB HID



Motherboard input type often plays role in choosing
interface method.


Off
-
the
-
shelf
unit (lowest cost)
limits interface flexibility


In
-
house design (expensive) allows for all options









USB HID


Serial (RS232)



Serial HID


USB
-
UART


Touch
screen performance controlled by
controller



Converts electronic
signal sent from
touch
sensor
to
the host
PC through a
I2C, serial

or USB interface in an X/Y format.



Two Types


PCB (traditional controller board)



Chip
-
on
-
Flex




PCAP Controller Challenges


False touch


Subject to EMI noise


Cost
can be
very expensive
depending on
capabilities


If slim design/space constraints, then
chip
-
on
-
flex


Custom firmware required for PCAP

Resistive
C
ontrollers


No real challenges with resistive electronics


Traditional resistive controller (4, 5, 8
-
wire) very low
cost


Multi
-
t
ouch resistive controllers are expensive


Chip
-
on
-
flex
not
an option (also
not needed
)


Easy to integrate or replace


Optical
Controllers


Any issues with them?

Insert Graphic

Firmware


Tells touch
screen what kind of touches or input to pay
attention to or
ignore


Can make touches
more or less
sensitive
(application specific)


Provides
system level EMI
shielding

Drivers


Mainstream OS drivers loaded on chip


Customer must write own drivers for custom OS


Drivers


Mainstream OS (Windows 7) drivers loaded on chip


Android, Linux drivers usually available from chip manufacturer


Customer must write own drivers for custom OS

Calibration


Projected Capacitive, Optical, MARS
-

one time calibration


Analog Resistive


periodic calibration


Jeff Carpenter

CEO
, Ringtail Design


What
are the advantages and limitations of software tools
used to develop touch applications?




How to choose the best software development method for
interactive platforms




See word document for software section outline.

Windows 7


Industry standard
touch screen platform


Supports multi
-
touch


Plug
and play


does not require additional drivers


Android


Supports
native
multi
-
touch


Additional
drivers needed to run touch
screen

Linux


Supports
native
multi
-
touch


Additional
drivers needed to run touch
screen


iOS
/Leopard


Supports
native
multi
-
touch


Additional
drivers needed to run touch
screen


All
operating systems available as embedded
O/S