Application Note AN_333 FT800 and FT801 Touch Capabilities

Application Note
AN_333
FT800 and FT801 Touch
Capabilities
Version 1.0
Issue Date: 2014-07-08
The FTDI EVE video controllers offer low cost solutions for embedded graphics
requirements. In addition to the graphics, touch inputs and an audio output
provide a complete human machine interface to the outside world.
This application note describes the differences between the resistive touch
interface on the FT8x0 and capacitive touch interface on the FT8x1.
Use of FTDI devices in life support and/or safety applications is entirely at the user’s risk, and the
user agrees to defend, indemnify and hold FTDI harmless from any and all damages, claims, suits
or expense resulting from such use.
Future Technology Devices International Limited (FTDI)
Unit 1, 2 Seaward Place, Glasgow G41 1HH, United Kingdom
Tel.: +44 (0) 141 429 2777 Fax: + 44 (0) 141 429 2758
Web Site: http://ftdichip.com
Copyright © 2014 Future Technology Devices International Limited
Application Note
AN_333 FT800 and FT801 Touch Capabilities
Version 1.0
Document Reference No.: FT_001074
Clearance No.: FTDI# 399
Table of Contents
1
2
Introduction .................................................................................................................................... 2
1.1
Touch Hardware...................................................................................................................... 2
1.2
Touch Features........................................................................................................................ 4
1.3
Capacitive Touch Types ........................................................................................................... 4
1.3.1
Mutual Capacitance ........................................................................................................ 4
1.3.2
Self Capacitance .............................................................................................................. 4
Touch Feature Description .............................................................................................................. 5
2.1
Compatibility Mode vs Original FT800 .................................................................................... 5
2.1.1
2.2
3
Limitations....................................................................................................................... 5
Extended Mode vs Original FT800 .......................................................................................... 5
2.2.1
Touch Point Index ........................................................................................................... 5
2.2.2
Limitations....................................................................................................................... 5
Contact Information........................................................................................................................ 6
Appendix A – References ........................................................................................................................ 7
Document References......................................................................................................................... 7
Acronyms and Abbreviations .............................................................................................................. 7
Appendix B – List of Tables & Figures ..................................................................................................... 8
List of Tables ....................................................................................................................................... 8
List of Figures ...................................................................................................................................... 8
Appendix C – Revision History ................................................................................................................ 9
1
Copyright © 2014 Future Technology Devices International Limited
Application Note
AN_333 FT800 and FT801 Touch Capabilities
Version 1.0
Document Reference No.: FT_001074
Clearance No.: FTDI# 399
1 Introduction
EVE, or the Embedded Video Engine, is a family of ICs designed to control TFT displays. In addition
to controlling the display, the EVE family also includes embedded support for touch control and
audio output.
The device is controlled over a low bandwidth SPI or I2C interface allowing interface to nearly any
microcontroller with a SPI or I2C master port. Simple and low-pin-count microcontrollers can now
have a high-end graphical user interface by using the EVE technology.
Unique to EVE, images are rendered on a line by line basis. This eliminates the need for an
external, and costly, frame buffer. EVE connects directly between the MCU and LCD panel.
The User Interface is managed by the MCU and displayed by the EVE graphics controller. The
integrated PWM audio processor provides single-channel sound and file playback. Touch feedback
is handled by the integrated resistive touch controller on the FT800 devices or an I2C master to a
capacitive touch controller with the FT801. Interaction to all three controllers on the FT800 and
FT801 – video, touch and audio – is accomplished through a single microcontroller interface.
1.1 Touch Hardware
The FT800 devices support resistive touch screens and provide a direct connection for the X and Y
inputs. The FT801 devices support an interface to an external capacitive touch controller which is
typically integrated into the LCD panel assembly. While the video and audio operation is identical
between the two series, this document provides a comparison of the different touch features.
As noted in Table 1.1, below, the only differences between the FT800 and FT801 series is the
touch interface. The FT800 follows the original FT800 with a direct X, Y analog input. The FT801,
however replaces the analog input with an I2C master that is specifically directed to two external
capacitive touch controllers: Azoteq and focaltech. Fortunately, one of these external touch
controllers is usually available integrated with the LCD assembly. The controller IC typically does
not need to be separately added to the design.
Hardware Feature
FT800 (resistive)
FT801 (capacitive)
Video
Identical
Identical
Audio
Identical
Identical
Touch Interface
Direct X± and Y±
I2C to external controller
Touch Controller
Integrated to FT800
External, usually integrated on
the LCD panel assembly
Supported Touch Controllers
Integrated
Azoteq and focaltech
Table 1.1 - EVE Touch Hardware Comparison
The MCU, LCD and audio connections are identical between the two series. Only the touch
interface is different through the addition of an external controller.
2
Copyright © 2014 Future Technology Devices International Limited
Application Note
AN_333 FT800 and FT801 Touch Capabilities
Version 1.0
Document Reference No.: FT_001074
Clearance No.: FTDI# 399
Figure 1.1 - FT800 - Resistive Touch Connection
Figure 1.2 - FT801 - Capacitive Touch Connection
3
Copyright © 2014 Future Technology Devices International Limited
Application Note
AN_333 FT800 and FT801 Touch Capabilities
Version 1.0
Document Reference No.: FT_001074
Clearance No.: FTDI# 399
1.2 Touch Features
The FT801 EVE controllers have two modes for touch. Compatibility mode mimics the FT800
resistive touch operation and supports a single touch point. Extended mode allows up to 5
simultaneous multi-touch points which is useful when panning and zooming an image. Each
feature is noted in Table 1.2, below.
Touch Feature
FT800
resistive
FT801
capacitive
compatibility mode
FT801
capacitive
extended mode
Simultaneous Points
1
1
5
Calibration
Yes
Yes
No
Sampling Frequency
Approx. 1,000 Hz
80-100 Hz
80-100 Hz
Operating Modes
Off
One-Shot
Frame-Sync
Continuous
Off
One-Shot
Off
One-Shot
Continuous
Continuous
Interrupt on touch
Yes
No
No
Sketch
cmd_sketch
cmd_csketch
cmd_csketch
Tags
Single tag at one time
Single tag at one time
First touch is tagged –
remainder of
simultaneous touches
use coordinates
Power Mode
Inactive in
POWERDOWN
External controller is
active in
POWERDOWN
External controller is
active in
POWERDOWN
Table 1.2 - EVE Touch Features
1.3 Capacitive Touch Types
There are a variety of different construction techniques in capacitive touch displays and different
controller ICs are suitable for different display types. The FT801 supports the Focaltech FT5x06
series or Azotech IQS5xx series of touch controllers.
1.3.1
Mutual Capacitance
With mutual capacitance, a capacitor is located at each intersection of the row and column grid.
One direction is driven. Bringing a finger close to the surface changes the local electrostatic field
and each of the capacitors are measured, allowing for accurate detection and location of more than
one touch. This is supported by the Azoteq devices.
1.3.2
Self-Capacitance
With a similar construction as mutual capacitance, here the rows and columns operate
independently. While it may provide a stronger signal, only one touch point can be accurately
sensed. This is supported by the Focaltech devices.
4
Copyright © 2014 Future Technology Devices International Limited
Application Note
AN_333 FT800 and FT801 Touch Capabilities
Version 1.0
Document Reference No.: FT_001074
Clearance No.: FTDI# 399
2 Touch Feature Description
2.1 Compatibility Mode vs Original FT800
When in compatibility mode, the capacitive touch controller is configured to allow a single touch
point. This method allows direct compatibility with the original FT800. All tag features are
identical. The only difference is the touch controller does not generate an interrupt so the touch
information must be polled.
2.1.1




Limitations
Sketch: There are separate resistive (cmd_sketch) and capacitive (cmd_csketch) calls to
account for the different data polling rates required for each display type.
Touch Frequency: Lower than resistive at ~100Hz
Operation mode: FRAME-SYNC – collecting touch data while the screen is not actively
drawing an image – is not available
Interrupt: not available for capacitive touch
2.2 Extended Mode vs Original FT800
When in extended mode, the capacitive touch controller allows up to 5 simultaneous touch points.
2.2.1
Touch Point Index
The first point is assigned touch zero. Successive points are assigned the next index up to 4. The
index is maintained until the touch is released (finger-up). Once the touch is released, the index is
freed up for the next touch. For example if the following sequence happened:
a)
b)
c)
d)
e)
f)
g)
Finger
Finger
Finger
Finger
Finger
Finger
Finger
1
2
3
2
4
1
5
down = index 0 and assigned tag
down = index 1, no tag
down = index 2, no tag
up = index 1 freed
down = index 1 – this is re-assigned at this point, no tag
up = index 0 freed
down = index 0 and assigned tag
While a finger is down, the finger location is updated if it moves around the screen.
2.2.2





Limitations
Sketch: There are separate resistive (cmd_sketch) and capacitive (cmd_csketch) calls to
account for the different data polling rates required for each type.
Calibration: Calibration is not available for extended mode.
Operation mode: FRAME-SYNC – collecting touch data while the screen is not actively
drawing an image – is not available
Tags: Only the first touch point (index 0) is assigned a tag. Host MCU must identify all
other points based on X,Y data.
Interrupt: not available for capacitive touch
5
Copyright © 2014 Future Technology Devices International Limited
Application Note
AN_333 FT800 and FT801 Touch Capabilities
Version 1.0
Document Reference No.: FT_001074
Clearance No.: FTDI# 399
3 Contact Information
Head Office – Glasgow, UK
Branch Office – Tigard, Oregon, USA
Future Technology Devices International Limited
Unit 1, 2 Seaward Place, Centurion Business Park
Glasgow G41 1HH
United Kingdom
Tel: +44 (0) 141 429 2777
Fax: +44 (0) 141 429 2758
Future Technology Devices International Limited
(USA)
7130 SW Fir Loop
Tigard, OR 97223-8160
USA
Tel: +1 (503) 547 0988
Fax: +1 (503) 547 0987
E-mail (Sales)
E-mail (Support)
E-mail (General Enquiries)
sales1@ftdichip.com
support1@ftdichip.com
admin1@ftdichip.com
E-Mail (Sales)
E-Mail (Support)
E-Mail (General Enquiries)
us.sales@ftdichip.com
us.support@ftdichip.com
us.admin@ftdichip.com
Branch Office – Taipei, Taiwan
Branch Office – Shanghai, China
Future Technology Devices International Limited
(Taiwan)
2F, No. 516, Sec. 1, NeiHu Road
Taipei 114
Taiwan , R.O.C.
Tel: +886 (0) 2 8791 3570
Fax: +886 (0) 2 8791 3576
Future Technology Devices International Limited
(China)
Room 1103, No. 666 West Huaihai Road,
Shanghai, 200052
China
Tel: +86 21 62351596
Fax: +86 21 62351595
E-mail (Sales)
E-mail (Support)
E-mail (General Enquiries)
E-mail (Sales)
E-mail (Support)
E-mail (General Enquiries)
tw.sales1@ftdichip.com
tw.support1@ftdichip.com
tw.admin1@ftdichip.com
cn.sales@ftdichip.com
cn.support@ftdichip.com
cn.admin@ftdichip.com
Web Site
http://ftdichip.com
System and equipment manufacturers and designers are responsible to ensure that their systems, and any Future Technology
Devices International Ltd (FTDI) devices incorporated in their systems, meet all applicable safety, regulatory and system-level
performance requirements. All application-related information in this document (including application descriptions, suggested
FTDI devices and other materials) is provided for reference only. While FTDI has taken care to assure it is accurate, this
information is subject to customer confirmation, and FTDI disclaims all liability for system designs and for any applications
assistance provided by FTDI. Use of FTDI devices in life support and/or safety applications is entirely at the user’s risk, and the
user agrees to defend, indemnify and hold harmless FTDI from any and all damages, claims, suits or expense resulting from
such use. This document is subject to change without notice. No freedom to use patents or other intellectual property rights is
implied by the publication of this document. Neither the whole nor any part of the information contained in, or the product
described in this document, may be adapted or reproduced in any material or electronic form without the prior written consent
of the copyright holder. Future Technology Devices International Ltd, Unit 1, 2 Seaward Place, Centurion Business Park,
Glasgow G41 1HH, United Kingdom. Scotland Registered Company Number: SC136640
6
Copyright © 2014 Future Technology Devices International Limited
Application Note
AN_333 FT800 and FT801 Touch Capabilities
Version 1.0
Document Reference No.: FT_001074
Clearance No.: FTDI# 399
Appendix A – References
Document References
http://en.wikipedia.org/wiki/Touchscreen#Capacitive
FT800 Datasheet
FT801 Datasheet
Acronyms and Abbreviations
Terms
Description
EVE
Embedded Video Engine
I2C
Inter Integrated Circuit
SPI
Serial Peripheral Interface
PCAP
Projected Capacitive Touch (also PCT)
7
Copyright © 2014 Future Technology Devices International Limited
Application Note
AN_333 FT800 and FT801 Touch Capabilities
Version 1.0
Document Reference No.: FT_001074
Clearance No.: FTDI# 399
Appendix B – List of Tables & Figures
List of Tables
Table 1.1 - EVE Touch Hardware Comparison ......................................................................... 2
Table 1.2 - EVE Touch Features ............................................................................................ 4
List of Figures
Figure 1.1 - FT800 - Resistive Touch Connection ..................................................................... 3
Figure 1.2 - FT801 - Capacitive Touch Connection ................................................................... 3
8
Copyright © 2014 Future Technology Devices International Limited
Application Note
AN_333 FT800 and FT801 Touch Capabilities
Version 1.0
Document Reference No.: FT_001074
Clearance No.: FTDI# 399
Appendix C – Revision History
Document Title:
AN_333 FT800 and FT801 Touch Capabilities
Document Reference No.:
FT_001074
Clearance No.:
FTDI# 399
Product Page:
http://www.ftdichip.com/EVE.htm
Document Feedback:
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Revision
1.0
Changes
Initial Release
Date
2014-07-08
9
Copyright © 2014 Future Technology Devices International Limited