Features
• Complete Module for Standalone Use:
•
•
•
•
•
•
– Atmel XMEGA256A3BU MCU
– Projected Capacitive Multi Touch Controller
– 2.8in LCD
– USB Connectivity
– SD Card
– Expansion Header for Development (PCB Rev A2)
MCU:
– ATXMEGA256A3BU
– 256KBytes Flash / 8Kbytes Boot
– 16KBytes RAM
– 4KBytes EEPROM
– USB 2.0 Full speed (12Mbps) and low speed (1.5Mbps)
Storage:
– SD/MMC
Touch:
– Atmel maXTouch mXT143E Touch Controller
– Supports up to 8 touches
Display:
– Displaytech SDT028ATFT 2.8in LCD
– 320x240 resolution
– 20 ms typical response time
– SPI interface via ILI9341 / ILI9320 (or compatible)
– Optional support for 18-bit parallel interface
– White LED backlight
Cover Panel:
– 1.2mm Soda Lime Glass
– Optional 0.7mm Gorilla Glass™
Expansion Header: (PCB Rev A2)
– Hirose DF40C series mezzanine
connector
– I2C, SPI and USART Buses
– Interrupts
– I/O
– ADC, DAC, Analog Comparator
– Timer OC, PWM/AWeX
PDA TM2801:
2.8in PCAP
Touch Module
1303-5-6
Contents
1
2
Module Overview
1.1
PCB Connections
4
1.2
Debug Connector J1
6
1.3
Touch Sensor Flex Connector J2
6
1.4
Display Flex Connector J3
7
1.5
Programming/Debug J4
7
1.6
Universal Serial Bus (USB) J5
8
1.7
Expansion J6
8
1.8
SD/MMC U5
9
1.9
XMEGA U4
10
Overview of the 2.8in PCAP Touch Module
Introduction
11
2.2
Understanding Unfamiliar Concepts
12
2.3
XMEGA A3BU Microcontroller
12
Atmel Software Framework
12
2.4
LCD Panel
2.4.1
2.5
2.6
maXTouch Controller Interface
SD/MMC Connector
2.6.1
2.7
2
Atmel Software Framework
maXTouch Capacitive Touchscreen Controller
2.5.1
4
11
2.1
2.3.1
3
4
Atmel Software Framework
Expansion Interface
Getting Started
12
13
13
13
14
14
14
15
3.1
Hardware Setup
15
3.2
Demo Firmware
15
3.3
Loading Firmware
15
3.3.1
Programming Tools
15
3.3.2
Programming the Example Code
15
Specifications
16
4.1
Mechanical Specifications
16
4.2
Absolute Maximum Specifications
18
4.3
Recommended Operating Conditions
18
4.4
DC Specifications
18
4.5
I2C-compatible Bus Specifications
18
4.6
Power Consumption
19
PDA TM2801: 2.8in PCAP Touch Module
1303-5-6
PDA TM2801:
4.7
5
Part Number
2.8in PCAP Touch Module
19
I2C Basics (I2C-compatible Operation)
20
5.1
Interface Bus
20
5.2
Transferring Data Bits
20
5.3
START and STOP Conditions
20
5.4
Address Byte Format
21
5.5
Data Byte Format
21
5.6
Combining Address and Data Bytes into a Transmission
22
6
Revision History
23
7
Notes
24
3
1
Module Overview
1.1 PCB Connections
USB SD/MMC
Debug /
Programming
J5
U5
Pin 1
J4
Pin 1
TouchJ2
Sensor Flex
J3 Display
Flex
AT M EL
XM EGA256A3BU
AT M EL
MXT143E
J1
Debug
Pin 1
Pin 1
Figure 1 - PCB Connectors (10-01034-A1)
4
PDA TM2801: 2.8in PCAP Touch Module
1303-5-6
PDA TM2801:
2.8in PCAP Touch Module
USB SD/MMC
Debug /
Programming
J5
U5
Pin 1
J4
Pin 1
Touch
Sensor Flex J2
Display
J3 Flex
AT M EL
XM EGA256A3BU
AT M EL
MXT143E
Pin 1
Pin 1
J6
Expansion
Figure 2 – Main PCB Connectors (10-01034-A2)
NOTE: The SD/MMC Slot (U5) is on the underside of the PCB
Pin 1
Pin 1
Figure 3 – Expansion PCB (10-01052-A0)
The following abbreviations and notations are used for the pin descriptions below. Note signal direction is given
with respect to the touch module and on-board MCU – not the device connected:
maXTouch touchscreen
LCD
LCD Panel
SD
SD/MMC
USB
Universal Serial Bus
Exp
Expansion (PCB Rev A2 or greater)
MXT
I
Input only
O
Output only, push-pull
XMega Port
Identification of XMega Port/Pin
OD
Open drain output
P
Power or Ground
5
1.2 Debug Connector J1
Connector J1 carries signals used to debug the MaXTouch Touchscreen Controller. Debug Connector is only
present on the 10-01034-A1 revision PCB. As of the 10-01034-A2 revision PCB, these signals are accessible on
the Expansion connector.
Pin
Type
Description
Pin
Type
Description
2
1
P
+5Vdc
6
I/O
2
-
N/C
7
I
~MXT_RESET (1)
3
O
~MXT_CHG (1)
8
P
GND
4
-
N/C
9
O
MXT DBG DATA
10
O
MXT DBG CLK
5
I
2
I C SDA
(2)
I C SCL
(2)
NOTE 1 – Pulled up through 47kΩ resistor
NOTE 2 – Pulled up through 3.3kΩ resistor
1.3 Touch Sensor Flex Connector J2
Connector J2 connects to the touch sensor flex and carries signals used by the maXTouch controller to detect
input on the touch sensor.
6
Pin
Type
1
I/O
2
I/O
3
Description
Pin
Type
X1
14
I/O
Y6
X3
15
I/O
Y7
I/O
X5
16
I/O
Y8
4
I/O
X7
17
I/O
Y9
5
I/O
X9
18
I/O
Y10
6
I/O
X11
19
P
GND
7
P
GND
20
I/O
X12
8
I/O
Y0
21
I/O
X10
9
I/O
Y1
22
I/O
X8
10
I/O
Y2
23
I/O
X6
11
I/O
Y3
24
I/O
X4
12
I/O
Y4
25
I/O
X2
13
I/O
Y5
26
I/O
X0
PDA TM2801: 2.8in PCAP Touch Module
Description
1303-5-6
PDA TM2801:
2.8in PCAP Touch Module
1.4 Display Flex Connector J3
Connector J3 connects to the LCD panel flex and carries signals between the host and the LCD panel.
Pin
Type
1
P
2
3
Description
Pin
Type
Description
Vin
24
O
GND (DB8)
P
LED_K1 (Backlight Cathode)
25
O
GND (DB7)
P
LED_K2 (Backlight Cathode)
26
O
GND (DB6)
4
P
LED_K3 (Backlight Cathode)
27
O
GND (DB5)
5
P
LED_K4 (Backlight Cathode)
28
O
GND (DB4)
6
-
N/C (IM0)
29
O
GND (DB3)
7
-
N/C (IM1)
30
O
GND (DB2)
8
-
N/C (IM2)
31
O
GND (DB1)
9
-
N/C (IM3)
32
O
GND (DB0)
10
-
N/C (FMARK)
33
O
~CS (1)
11
O
GND (VSYNC)
34
O
WR
12
O
GND (HSYNC)
35
O
RS / SCL
13
O
GND (DOTCLK)
36
O
GND (RD)
14
O
GND (ENABLE)
37
O
RESET (1)
15
O
GND (DB17)
38
I
SDO
16
O
GND (DB16)
39
O
SDI
17
O
GND (DB15)
40
P
Vdd
18
O
GND (DB14)
41
P
GND
19
O
GND (DB13)
42
-
Reserved (RES1)
20
O
GND (DB12)
43
-
Reserved (mXT ~CHG) (1)
21
O
GND (DB11)
44
-
Reserved (SDA) (2)
22
O
GND (DB10)
45
-
Reserved (SCL)
23
O
GND (DB9)
(2)
NOTE 1 – Pulled up through 47kΩ resistor
NOTE 2 – Pulled up through 3.3kΩ resistor
1.5 Programming/Debug J4
Connector J4 connects to the MCU’s PDI programming and debug interface.
Pin
Type
1
I/O
2
3
Description
Pin
Type
Description
PDI_DAT
4
-
N/C
P
Vdd
5
I
~RESET / PDI_CK
-
N/C
6
P
GND
7
1.6 Universal Serial Bus (USB) J5
Connector J5 connects to the MCU’s USB interface.
Pin
Type
1
P
2
Description
Pin
Type
Description
+5VBUS
6
P
GND
I/O
D-
7
P
GND
3
I/O
D+
8
P
GND
4
-
N/C
9
P
GND
5
P
GND
1.7 Expansion J6
Connector J6 ( Hirose DF40-C-30DS-0.4V(51) ) provides access to many system signals as well as additional I/O
and signals to support development and prototyping. The Expansion Interface PCB (10-01052-A0) can be used
to access these signals. Signals on the Expansion PCB follow the same sequence as shown in the table below.
See section 2.7 for additional details.
1
P
2
P
3
I/O
4
O
Description
Vin
Vin
I2C SDA (2)
2
I C SCL
(2)
5
I
~MXT_CHG
6
O
WR
(1)
(1)
Pin
Type
16
I
Description
MXT
LCD
SD
XMega
Port
Pin Type
MXT
LCD
SD
XMega
Port
Note: Some signals provided through the Expansion Interface are used by the system – these signals are
indicated via gray highlighting in the table below. Care should be taken when using this interface and
these pins in particular to ensure the effect on system operation is understood and no damage will occur.
Refer to the Atmel XMega256A3BU datasheet for details on available pin functions.
~SD_Detect (1)
B1
(1)
17
O
~RESET_LCD
C0
18
I/O
INT, ADC, AC, DAC
B3
C1
19
I/O
INT, ADC, AC, DAC, JTAG
B4
C2
20
I/O
INT, ADC, AC, DAC, JTAG
B5
C3
21
I/O
INT, ADC, AC, DAC, JTAG
B6
C4
22
I/O
INT, ADC, AC, DAC, JTAG
B7
O
LED_EN
XMEGA: ~RESET / PDI_CK
7
O
~CS
8
O
MOSI
C5
23
9
I
MISO
C6
24
I
10
O
SCK
C7
25
I/O
XMEGA: PDI_DAT
11
I/O
INT, TC, I2C: SDA
E0
26
O
~RESET_MXT (1)
12
I/O
INT, TC, I2C SCL,USART: XCK
E1
27
O
MXT DBG DATA
13
I/O
INT, TC, USART: RXD
E2
28
O
MXT DBG CLK
14
I/O
INT, TC, USART: TXD
E3
29
P
GND
15
O
~SD_CS (1)
B0
30
P
GND
B2
F0
A7
NOTE 1 – Pulled up through 47kΩ resistor
NOTE 2 – Pulled up through 3.3kΩ resistor
8
PDA TM2801: 2.8in PCAP Touch Module
1303-5-6
PDA TM2801:
2.8in PCAP Touch Module
1.8 SD/MMC U5
The SD/MMC Connector U5 connects to the MCU’s SPI and I/O.
Pin
Type
Description
(1)
Pin
Type
Description
9
-
N/C (SD DAT2)
1
O
~SD_CS (SD DAT3)
2
O
MOSI (SD CMD)
10
I
~SD_Detect (SD C/D) (1)
3
P
GND
11
P
GND
4
P
Vdd
12
-
N/C (SD W/P)
5
O
SCK (SD CLK)
13
P
GND (SD SHELL)
6
P
GND
14
P
GND (SD SHELL)
7
I
MISO (SD DAT0)
15
P
GND (SD SHELL)
8
-
N/C (SD DAT1)
16
P
GND (SD SHELL)
NOTE 1 – Pulled up through 47kΩ resistor
9
1.9 XMEGA U4
Type
Description
Pin
Type
1
-
2
-
N/C
34
P
GND
N/C
35
P
Vdd
3
O
LED-
36
-
4
-
N/C
5
O
~RESET_MXT (1)
6
O
~SD_CS (1)
7
I
8
O
9
-
10
~SD_Detect
(1)
~RESET_LCD
(1)
-
Description
Expansion Interface(3) (E0)
(3)
-
Expansion Interface
(E1)
-
Expansion Interface(3) (E2)
Expansion Interface(3) (E3)
39
-
40
-
N/C
41
-
N/C
42
-
N/C
Expansion Interface
(3)
(B4)
43
-
N/C
(3)
11
-
Expansion Interface
(B5)
44
P
GND
12
-
Expansion Interface(3) (B6)
45
P
Vdd
46
O
LED_EN
(3)
13
-
14
P
GND
47
-
N/C
15
P
Vdd
48
-
N/C
16
I/O
-
N/C
-
N/C
17
O
Expansion Interface
I2C SDA (2)
2
I C SCL
(2)
18
I
~MXT_CHG
19
O
WR
(1)
(1)
(B7)
37
38
Expansion Interface(3) (B3)
MXT
LCD
SD
USB
Exp
Pin
MXT
LCD
SD
USB
Exp
The MCU’s pins are assigned as shown below. Note a pin’s functionality within the system is indicated in the
columns located to the right of the description.
49
50
51
-
N/C
52
P
GND
53
P
Vdd
20
O
~CS
21
O
MOSI
54
-
N/C
22
I
MISO
55
-
N/C
23
O
SCK
56
I/O
24
P
GND
57
25
P
Vdd
26
-
Reserved (RES1)
27
-
28
29
PDI_DAT
I
~RESET / PDI_CK
58
-
N/C
59
-
N/C
N/C
60
P
GND
O
LED D4
61
P
Vdd
O
LED D5
62
-
N/C
30
O
LED D2
63
-
N/C
31
O
LED D3
64
-
N/C
32
I/O
D-
65
P
GND (Thermal Pad)
33
I/O
D+
NOTE 1 – Pulled up through 47kΩ resistor
NOTE 2 – Pulled up through 3.3kΩ resistor
NOTE 3 – Expansion Interface not available on PCB Rev A1
10
PDA TM2801: 2.8in PCAP Touch Module
1303-5-6
PDA TM2801:
2.8in PCAP Touch Module
2 Overview of the 2.8in PCAP Touch Module
2.1 Introduction
The 2.8in PCAP Touch Module is a touchscreen module offering best-in-class projected capacitance multi-touch
functionality combined with a 2.8in LCD panel.
With an onboard Atmel XMEGA256A3BU MCU, the module offers standalone operation based on a subset of
functionality available from the Atmel XMEGA A3BU Xplained MCU Board and Atmel mXT143E Xplained Module.
The module has been designed to effectively reproduce the combined schematic of these Xplained boards:
Atmel XMEGA A3BU Xplained MCU Board
Atmel mXT143E Routing Board
=
PDA TM2801 2.8in
PDA TM2800 mXT143E Xplained Board
+
Expansion Interface
As shown in Figure 4 below, the module MCU offers access to the touchscreen controller, display interface, USB
and storage for easy development and integration.
PDA 2.8in PCAP Touch Module
PCB
Capacitive Touchscreen
Controller
J2
mXT143E
J3
J5
MCU
LCD Panel
U5
XMEGA256
A3BU
Touch sensor
USB
HOST
SD Card
LOCK
LED D2
LED D3
SDSC card
LED D4
LED D5
J6
Expansion Interface
Figure 4 - Functional Block Diagram
11
2.2 Understanding Unfamiliar Concepts
Throughout this document, the functionality of the module sub-system will be outlined and summarized. However,
the user is encouraged to refer to the resources and documents below in order to gain a more thorough
understanding of each sub-system.
• Atmel XMega256A3BU (www.atmel.com)
• Atmel maXTouch mXT143E Datasheet (www.atmel.com)
• Displaytech SDT028ATFT Datasheet (www.displaytech-us.com)
• For a basic overview of I2C communication, refer to Section 5 of this document
• Universal Serial Bus (www.usb.org)
• Secure Digital Card (www.sdcard.org)
2.3 XMEGA A3BU Microcontroller
The module is designed around the Atmel XMEGA256A3BU microcontroller. This microcontroller has a variety of
features and flexibility and provides a good starting point for development and evaluation of the PDA TM2801
touch module. For additional details, see the XMEGA documentation available from Atmel’s website
(www.atmel.com).
The MCU is directly connected to all of the module sub-systems, providing a capable full-featured platform for
development.
2.3.1 Atmel Software Framework
The Atmel Software Framework or ASF (http://asf.atmel.com) contains example projects targeting the
XMEGA256A3BU MCU and its various features. This provides an excellent resource, in combination with the
XMEGA documentation, for the user to become acquainted with the capabilities of the MCU. Of particular interest
with this module, the ASF contains sample code for implementing the USB device interface available on the
XMEGA256A3BU.
2.4 LCD Panel
The module MCU has a direct connection to the LCD panel interface (Connector J3) which includes a serial
interface to the ILI9341 (or ILI9320 or compatible) display driver IC and LED backlight control. The LCD Backlight
control is performed using the LED_EN and LED- signals (XMEGA U4 Pins 46 and 3, respectively) as shown in
Figure 5 below:
12
PDA TM2801: 2.8in PCAP Touch Module
1303-5-6
PDA TM2801:
2.8in PCAP Touch Module
3
LED_K
R8
3.3k
Q1
2N7002
1
2
LED_EN
LED-
R9
47k
R10
33
C6
0.1uF
Figure 5 - LED Backlight Control
2.4.1 Atmel Software Framework
The Atmel Software Framework includes projects targeting the ILI9341 Display Driver IC.
2.5 maXTouch Capacitive Touchscreen Controller
The module touch screen interface is based on the Atmel maXTouch mXT143E Touch Controller.
The touch controller scans the touch sensor and signals the MCU with an active low interrupt signal (~MXT_CHG)
when new touch data is available. Data communication with the maXTouch controller is performed over an I2C
interface (XMEGA U4 Pins 16, 17). The I2C address of the touch controller is set to 0x4A.
NOTE: Pull-up resistors for the I2C SCL and SDA lines are located at R4 and R3 respectively. A pull-up resistor for
the ~MXT_CHG interrupt signal is located at R6.
2.5.1 maXTouch Controller Interface
Details of the maXTouch communication protocol are beyond the scope of this document. However information is
provided below to facilitate evaluation and initial development.
The module is pre-loaded with a configuration already optimized for this touch sensor and panel, so the
developer need only focus on interfacing with the device. When developing the maXTouch controller
interface during evaluation and development, care should be taken to avoid changing the maXTouch
configuration or committing changes to NV storage on the maXTouch controller.
To get started with development, the user is strongly encouraged to leverage existing code available from the
resources outlined in the following sections.
2.5.1.1
Atmel Software Framework
The Atmel Software Framework (http://asf.atmel.com) contains examples of code for interfacing with devices in the
maXTouch family of touch controllers. Many of the code examples found in the ASF are targeted for the
mXT143E Xplained module and support the XMEGA256A3BU as the host MCU. With very minor modification,
these projects are directly applicable to this module.
2.5.1.2
Linux Kernel / Android
While the Linux or Android OS may not be applicable to XMEGA256A3BU, there is a growing code base in the
Linux and Android communities that can interface with maXTouch touchscreen controllers. These drivers provide
an excellent starting point for development with embedded firmware running on the XMEGA.
The Linux Kernel (www.kernel.org) has included basic support for maXTouch devices since version 2.6.36. The
mainline driver has undergone considerable evolution since then.
13
In addition, Atmel maintains patches (www.github.com/atmel-maxtouch/linux) which provide numerous out-of-cycle
improvements to the mainline Linux Kernel driver.
2.6 SD/MMC Connector
The module includes a SD/MMC Connector (Connector U5) to provide optional removable storage in the user’s
developments. This feature is currently experimental.
2.6.1 Atmel Software Framework
The Atmel Software Framework (in additional to many online resources) includes example projects that implement
SD/MMC support.
2.7 Expansion Interface
As of PCB revision A2, the Debug connector is replaced with an Expansion Connector (Connector J6). In
addition to the signals previously available through the Debug Connector, the expansion interface provides
broader access to system signals, spare I/O and a selection signals to support prototyping and development. The
Main PCB uses the Hirose DF40-C-30DS-0.4V(51) mezzanine connector.
The accompanying Expansion PCB (10-01052-A0) uses the Hirose DF40-C-30DP-0.4V(51) mezzanine connector.
Signals on the Expansion PCB are routed one-to-one from the mezzanine connector to an array of through-holes
suitable for direct soldering or populating with any configuration of connectors featuring 0.025in terminals with
0.100in pitch.
Note: Some signals provided through the Expansion Interface are used by the system for communication
with the LCD, Touchscreen Controller and SD/MMC interface and are of varying criticality to normal
operation. Care should be taken when using this interface. Refer to section 1.7 for details on which
signals are used elsewhere as well as the Atmel XMega256A3BU datasheet for details on available pin
functions.
14
PDA TM2801: 2.8in PCAP Touch Module
1303-5-6
PDA TM2801:
2.8in PCAP Touch Module
3 Getting Started
As previously noted, the module was designed to effectively consolidate the functionality of the XMEGA A3BU
Xplained and mXT143E Xplained board into a single, standalone module. This configuration provides a quick,
easy way to evaluate the performance of the touchscreen and display as well as offering a convenient platform for
development.
In addition, Atmel provides free development tools and coding resources to support development using Atmel
Studio (www.atmel.com) and the Atmel Software Framework (http://asf.atmel.com).
The following sections outline the process of setting up and programming the module.
3.1 Hardware Setup
The module is powered by the USB connector even if the USB interface to a host is not being used. Therefore,
the module can be powered either by connecting to a USB host or by connecting USB power supply.
3.2 Demo Firmware
The module is pre-loaded with example firmware to demonstrate basic touchscreen and display functionality.
This demo firmware will begin as soon as the device is powered up.
3.3 Loading Firmware
The user is encouraged to experiment with the various sample projects available in the Atmel Software Framework
(http://asf.atmel.com). In order demonstrate the functionality of the module, several of the example projects from
the ASF have been compiled for the XMEGA256A3BU and binary images (HEX files) are available for download
from the PDA website. See details below.
3.3.1 Programming Tools
Before the example HEX files can be loaded, you must first ensure that the necessary programmer (supporting PDI
programming) with associated driver/software is installed on your development system. Consult the manual
and/or support resources for your programmer for instructions on installation and use.
The programmer should be connected to the 6-pin PDI connector J4.
3.3.2 Programming the Example Code
Download the example HEX files from http://www.pdaatl.com/modules/2.8in/tm2801demo.zip and unzip to a
working folder. Files are named according to the example project.
15
4 Specifications
For complete specifications, refer to the datasheets listed in section 2.2 for the various sub-system components
outlined in Sections 2.4 and 2.5.
4.1 Mechanical Specifications
Drawings and CAD models available upon request.
51.0 mm
(PET Outline)
Cover Panel Outline
57.13mm x 81.61mm
R3.175mm in corners
1.2 mm (Cover Panel)
50.0 mm
User side
70.1 mm
(PET Outline)
58.6 mm
(Viewable)
Viewed from
user side
LCD side
0.460 mm (Sensor)
44.2 mm
(Viewable)
0.076 mm (FPC)
PIN 1
PCB contacts
face down
14.1 mm
5.42 mm
13.5 mm
(FPC Min Width)
PIN 26
4.65 mm
43 mm
(FPC Max Width)
Figure 6 - Sensor Only Dimensions
Sensor (P/N: 21-00001-A0) may be purchased individually.
Minimum order quantities apply. Contact PDA for details.
16
PDA TM2801: 2.8in PCAP Touch Module
1303-5-6
PDA TM2801:
2.8in PCAP Touch Module
7.7 mm
(PCB Component Clearance)
57.25 mm
(Frame Width)
10-01034-A2 Rev
10-01034-A1 Rev
52.7 mm
(PCB Length)
AT MEL
XM EGA2 56 A3BU
62.9 mm
(PCB Length)
50.8 mm
(PCB Width)
81.82 mm
(Frame Length)
AT M EL
MXT 143E
AT MEL
XM EGA2 56 A3BU
ATM EL
MXT143E
50.8 mm
(PCB Width)
19.83 mm
(Cover Panel rear surface
to Mounting Boss)
Figure 7 – Module Dimensions
17
4.2 Absolute Maximum Specifications
Parameter
Value
Operating temp
0oC to +70oC
Storage temp
-40oC to +85oC
Vdd
-0.5 to +3.6V
Max continuous pin current, any control or drive pin
±40 mA
Voltage forced onto any pin
-0.5V to (Vdd + 0.5) Volts
CAUTION: Stresses beyond those listed under Absolute Maximum Specifications may cause permanent
damage to the device. This is a stress rating only and functional operation of the device at these or other
conditions beyond those indicated in the operational sections of this specification are not implied. Exposure to
absolute maximum specification conditions for extended periods may affect device reliability.
4.3 Recommended Operating Conditions
Parameter
Value
Vin
3.3V ±5 percent
Supply ripple + noise
±20 mV
4.4 DC Specifications
Vdd = 3.3, Ta = recommended range, unless otherwise noted
Parameter
Description
Min
Typ
Max
Units
VIL
Low input logic level
- 0.5
–
0.3 Vdd
V
VHL
High input logic level
0.7 Vdd
–
Vdd + 0.5
V
VOL
Low output voltage
–
–
0.2Vdd
V
VOH
High output voltage
0.8Vdd
–
–
V
–
–
1
µA
IIL
Input leakage current
Notes
4.5 I2C-compatible Bus Specifications
18
Parameter
Operation
Address (maXTouch 143E)
0x4A
Maximum bus speed (SCL)
400 kHz
PDA TM2801: 2.8in PCAP Touch Module
1303-5-6
PDA TM2801:
I2C Specification
2.8in PCAP Touch Module
Version 2.1
4.6 Power Consumption
Vdd (V)
Mode
Idd (mA)
3.3Vdc
mxt143E in free run and LCD backlight
ON full.
60ma
4.7 Part Number
Part Number
Description
90-00003-A0
2.8” Touchscreen Module (PCB Rev A1)
90-00003-A1
2.8” Touchscreen Module with Expansion Interface (PCB Rev A2)
19
5 I2C Basics (I2C-compatible Operation)
5.1 Interface Bus
The device communicates with the host over an I2C-compatible bus, in accordance with version 2.1 of the I2C
specification. The following sections give an overview of the bus; more detailed information is available from
www.i2C-bus.org. Devices are connected to the I2C-compatible bus as shown in Figure 8 both bus lines are
connected to Vdd via pull-up resistors. The bus drivers of all I2C-compatible devices must be open-drain type. This
implements a wired “AND” function that allows any and all devices to drive the bus, one at a time. A low level on
the bus is generated when a device outputs a zero.
Figure 8.
I2C-compatible Interface Bus
Vdd
Device 1
Device 2
Device 3
Device n
R1
R2
SDA
SCL
5.2 Transferring Data Bits
Each data bit transferred on the bus is accompanied by a pulse on the clock line. The level of the data line must be
stable when the clock line is high; the only exception to this rule is for generating START and STOP conditions.
Figure 9.
Data Transfer
SDA
SCL
Data Stable
Data Stable
Data Change
5.3 START and STOP Conditions
The host initiates and terminates a data transmission. The transmission is initiated when the host issues a START
condition on the bus, and is terminated when the host issues a STOP condition. Between the START and STOP
conditions, the bus is considered busy. As shown in Figure 10 START and STOP conditions are signaled by
changing the level of the SDA line when the SCL line is high.
20
PDA TM2801: 2.8in PCAP Touch Module
1303-5-6
PDA TM2801:
Figure 10.
2.8in PCAP Touch Module
START and STOP Conditions
SDA
SCL
START
STOP
5.4 Address Byte Format
All address bytes are 9 bits long. They consist of 7 address bits, one READ/WRITE control bit and an acknowledge
bit. If the READ/WRITE bit is set, a read operation is performed. Otherwise a write operation is performed. An
address byte consisting of a slave address and a READ or a WRITE bit is called SLA+R or SLA+W, respectively.
When the device recognizes that it is being addressed, it acknowledges by pulling SDA low in the ninth SCL (ACK)
cycle.
The most significant bit of the address byte is transmitted first.
Figure 11.
Address Byte Format
Addr MSB
Addr LSB
R/W
ACK
7
8
9
SDA
SCL
1
2
START
5.5 Data Byte Format
All data bytes are 9 bits long, consisting of 8 data bits and an acknowledge bit. During a data transfer, the host
generates the clock and the START and STOP conditions. The slave device is responsible for acknowledging the
reception. An acknowledge (ACK) is signaled by the slave device pulling the SDA line low during the ninth SCL
cycle. If the slave device leaves the SDA line high, a NACK is signaled.
Figure 12.
Data Byte Format
Addr MSB
Addr LSB
R/W
ACK
8
9
Aggregate
SDA
SDA from
Transmitter
SDA from
Receiver
SCL from
Master
1
SLA+R/W
2
7
Data Byte
STOP or
Next Data Byte
21
5.6 Combining Address and Data Bytes into a Transmission
A transmission consists of a START condition, an SLA+R or SLA+W, one or more data bytes and a STOP
condition. The wired “ANDing” of the SCL line is used to implement handshaking between the host and the device.
The device extends the SCL low period by pulling the SCL line low whenever it needs extra time for processing
between the data transmissions.
Figure 13 shows a typical data transmission. Note that several data bytes can be transmitted between the SLA+R
or SLA+W and the STOP.
Figure 13.
Byte Transmission
Addr
MSB
Addr
LSB R/W ACK
Data
MSB
Data
LSB ACK
SDA
SCL
1
START
22
2
7
SLA+R/W
8
PDA TM2801: 2.8in PCAP Touch Module
9
1
2
7
Data Byte
8
9
STOP
1303-5-6
PDA TM2801:
2.8in PCAP Touch Module
6 Revision History
Revision No.
History
Rev 1210-1-1 – Oct 2012
Preliminary Draft
Rev 1210-2-2 – Oct 19, 2012
Initial Release
Rev 1211-3-3 – Nov 20, 2012
Add notes to Figure 4 regarding sensor orientation and pin 1 location.
Add notes to Figure 1 identifying connectors and pin 1 locations.
Rev 1303-4-5 – Mar 28, 2013
Add details of new 10-01034-A2 PCB Rev with Expansion interface
Rev 1305-5-6 – May 30,2013
Update references to ILI9320 to include ILI9341 LCD driver IC
23
7 Notes
Precision Design Associates, Inc.
736 Johnson Ferry Rd, Suite C-270
Marietta, GA 30068
USA
email: sales@pdaatl.com
tel: (770)-971-4490
®
url: http://www.pdaatl.com
®
®
© 2013 Precision Design Associates. All rights reserved. Atmel , Atmel logo and combinations thereof, maXTouch , QTouch , and others are
registered trademarks of Atmel Corporation or its subsidiaries. Other terms and product names may be registered trademarks or trademarks of others.
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PDA TM2801: 2.8in PCAP Touch Module
1303-5-6
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