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Features
QTouch® Sensor Channels
Up to eight keys
Integrated Haptic Engine
Haptic events may be triggered by touch detection or controlled by a host
microcontroller over SPI
Data Acquisition
QTouchADC key measurement/touch detection method
Configurable measurement timing and averaging
Spread spectrum charge transfer
Raw data from channel measurement can be read over the SPI interface
GPIO Pins
12 dedicated bi-directional GPIO pins, plus up to 4 additional pins (replacing keys)
Configurable as software PWM Drive, digital inputs or outputs
Device setup
Device configuration may be stored in NVRAM
Operation
Power-On reset and brown-out detection
Internal calibrated oscillator
Key Outline Sizes
6 mm × 6 mm or larger (panel thickness dependent); widely different sizes and shapes
possible, including solid or ring shapes
Key Spacing
7 mm or more, center to center (panel thickness dependent)
Layers required
One
Electrode Materials:
Etched copper, silver, carbon, ITO
Electrode Substrates:
PCB materials; polyamide FPCB; PET films, glass
Panel materials:
Plastic, glass, composites, painted surfaces (low particle density metallic paints
possible)
Panel Thickness:
Up to 10 mm glass, 5 mm plastic (electrode size dependent)
Key Sensitivity:
Individually configured over SPI interface
Signal Processing:
Self-calibration, auto drift compensation, noise filtering
Patented Adjacent Key Suppression® (AKS®) technology to ensure accurate key
detection
Interface:
Master/Slave SPI interface, up to 750 kHz
Object-based communications protocol
Power:
2.0 V to 5.5 V
Packages:
32-pin 5 × 5 mm QFN RoHS compliant
32-pin 7 × 7 mm TQFP RoHS compliant
Atmel AT42QT1085
Eight-key QTouch® Touch Sensor IC
DATASHEET
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1. Pinout and Schematic
1.1 Pinout Configuration
GPIO11
GPIO10
RESET
CHANGE
KEY3
KEY2
GPIO6
GPIO7
GPIO8
HAPTIC_PWM
SS
MOSI
MISO
GPIO0
GPIO1
GPIO2
VDD
VSS
GPIO3
GPIO5 SCK
AVDD
KEY6 / GPIO13
GPIO9
VSS
KEY7 / GPIO12
KEY0
KEY1
1
2
3
4
5
6
7
817
18
19
20
21
22
23
24
32 31 30 29 28 27 26 25
910 11 16
15
14
13
12
HAPTIC_EN
GPIO4
KEY4 / GPIO15
KEY5 / GPIO14
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1.2 Pinout Descriptions
Table 1-1. Pin Listing
Pin Name Type Comments If Unused, Connect
To...
1GPIO0 I/O General Purpose IO Leave open
2GPIO1 I/O General Purpose IO Leave open
3GPIO2 I/O General Purpose IO Leave open
4VDD PPower –
5VSS PGround –
6GPIO3 I/O General Purpose IO Leave open
7GPIO4 I/O General Purpose IO Leave open
8GPIO5 I/O General Purpose IO Leave open
9GPIO6 I/O General Purpose IO Leave open
10 GPIO7 I/O General Purpose IO Leave open
11 GPIO8 I/O General Purpose IO Leave open
12 HAPTIC_EN OEnable pin for haptic amplifier Leave open
13 HAPTIC_PWM ODrive for haptic effects Leave open
14 SS ISPI Enable Pull up to VDD via a
100 k resistor
15 MOSI ISPI Data In Leave open
16 MISO OSPI Data Out Leave open
17 SCK ISPI Clock Leave open
18 AVDD PAnalog Power –
19 KEY6 / GPIO13 I/O Sense pin / General Purpose IO Leave open
20 GPIO 9 I/O General purpose IO Leave open
21 VSS PGround –
22 KEY7 / GPIO12 I/O Sense pin / General Purpose IO Leave open
23 KEY0 I/O Sense pin Leave open
24 KEY1 I/O Sense pin Leave open
25 KEY2 I/O Sense pin Leave open
26 KEY3 I/O Sense pin Leave open
27 KEY4 / GPIO15 I/O Sense pin / General Purpose IO Leave open
28 KEY5 / GPIO14 I/O Sense pin / General Purpose IO Leave open
29 RESET IReset, internal pull-up Leave open
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I Input only I/O Input and output
O Output only, push-pull OD Open drain output P Ground or power
30 CHANGE OD Status change indicator Leave open
31 GPIO10 I/O General Purpose IO Leave open
32 GPIO11 I/O Gene ral Purpose IO Leave open
Table 1-1. Pin Listing (Continued)
Pin Name Type Comments If Unused, Connect
To...
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1.3 Schematic
Figure 1-1. Typical Circuit
Check the following sections for component values:
Section 3.2 on page 8: Series resistors (Rs0 – Rs7)
Section 3.3 on page 8: Power Supply
22
19
28
27
26
25
24
23 Rs0
Rs1
Rs2
Rs3
Rs4
Rs5
Rs6
Rs7
K0
K1
K2
K3
K4
K5
K6
K7
VDD
VSS
GPIO_0
GPIO_1
GPIO_2
GPIO_3
GPIO_4
GPIO_5
GPIO_6
GPIO_7
GPIO_8
GPIO_9
GPIO_10
GPIO_11
GPIO_0
1
GPIO_1
2
GPIO_2
3
GPIO_3
6
GPIO_4
7
GPIO_5
8
GPIO_6
9
GPIO_7
10
GPIO_8
11
GPIO_9
20
GPIO_10
31
GPIO_11
32
Key_7 / GPIO_12
Key_6 / GPIO_12
Key_5 / GPIO_14
Key_4 / GPIO_15
HAPTIC_EN 12
HAPTIC PWM 13
14
15
16
17
4
18
21
5
29
30
33
CHANGE
RESET
SPI_SS
SPI_MOSI
SPI_MISO
SPI_SCK
GPIO_0
GPIO_1
GPIO_2
GPIO_3
GPIO_4
GPIO_5
GPIO_6
GPIO_7
GPIO_8
GPIO_9
GPIO_10
GPIO_11
HAPTIC EN
HAPTIC PWM
KEY 0
KEY 1
KEY 2
KEY 3
KEY 4/GPIO 15
KEY 5/GPIO 14
KEY 6/GPIO 13
KEY 7/GPIO 12
VDD
AVDD
VSS
VSS
VSS
CHANGE
RESET
SPI_SS
SPI_MOSI
SPI_MISO
SPI_SCK
R3 R4 R5
1 µF 100 nF
Regulated
VDD
VSS
Optional 1.2 W
resistor to reduce
AVdd noise
QT1085
Pin 33, which is the pad on the underside of the
device, should be connected to Vss.
For haptics information refer
to the Application Note
QTAN0085, Haptics Design
Guide
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2. Overview
2.1 Introduction
The AT42QT1085 (QT1085) is an easy to use QTouchADC mode sensor IC based on Atmel principles fo r robust
operation and ease of design. It is intended for any touch-key application.
There are four dedicated channels configured as keys (Key 0 – Key 3). There are 12 dedicated GPIO channels
(GPIO_0 – GPIO_11).
Another four channels can be configured as keys or GPIO channels (Key 4 – Key 7 or GPIO 12 – GPIO 15).
The QT1085 is capable of detecting proximity or touch on the channels configured as keys.
The keys can be constructed in different shapes and sizes. Refer to the Touch Sensors Design Guide and
Application Note QTAN0079, Buttons, Sliders and Wheels Sensor Design Guide, for more information on
construction and design methods (both downloadable from the Atmel website).
Each GPIO channel may be configured as a digital input or output. In output mode, a GPIO pin may be set to output
a PWM signal at any of 16 duty cycles (4-bit PWM). The QT1085 allows electrodes to project sense fields through
any dielectric such as glass or plastic.
This device has ma ny advanced features which provide for reliable, trouble -free operation over the life of the
product. In particular the QT1085 features advanced self-calibration, drift compensation, and fast thermal tracking.
The QT1085 can tolerate some fluctuations in the power supply, and in many applications will not require a
dedicated voltage regulator.
A full haptics engine is integrated into the device, allowing feedback effects to be triggered on key detection or
directly activated by a host microcontroller.
The QT1085 includes all signal processing functions necessary to provide stable sensing under a wide variety of
changing conditions. Only a few external parts are required for operation and no external Cs capacitors are required.
The QT1085 modulates its acquisition pulses in a spread-spectrum fashion in order to heavily suppress the effects of
external noise, and to suppress RF emissions. This provides greater noise immunity and eliminates the need for
external sampling capacitors, allowing touch sensing using a single pin.
2.2 Resources
The following document provides essential information on configuring the QT1085:
AT42QT1085 Protocol Guide
Other documents that may also be useful (available by contacting the Atmel Touch Technology division) are listed in
“Associated Documents” on page 28.
2.3 User Interface Layout and Options
2.3.1 Keys
There are eight keys available. Each can be individually enabled or disabled by setting a bit in the Key T13 object
(one for each key).
2.3.2 GPIO Ports
There are 12 dedicated configurable General Purpose Input Output (GPIO) pins. Up to four additional GPIO pins can
be achieved by replacing four of the keys. The GPIO pins can be enabled or disabled by setting a bit in the GPIO
Configuration T29 object.
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2.3.3 Guard Channel
A guard channel may be used to prevent accidental touch detection on other keys which share the same Adjacent
Key Suppression (AKS) group. The guard channel is made more sensitive than the others in the AKS group through
a larger touch electrode area combined with higher gain / lower threshold. The QT1085 remains in Idle mode while a
guard channel is in detect, and Touch Automatic Calibration will not occur for a guard key detection.
2.4 Proximity Effect
Any channel can function as a proximity sensor, based on hand or body proximity to a produc t. This is achieved by
using a relatively large electrode and tuning the QTouchADC and Threshold configuration options. Refer to
QTAN0087, Proximity Design Guide, for more information.
2.5 SPI Interface
The QT1085 is an SPI slave-mode device, utilizing a four-wire full-duplex SPI interface.
There are four standard SPI signals: SS, SCK, MOSI and MISO.
The QT1085 also provides a CHANGE signal to indicate when there is a message waiting to be read. This removes
the need for the host to poll the QT1085 continuously.
Communications are performed through Read and Write operations on the Object Protocol memory map.
2.6 Operating Modes
Cycle times, Free-run and Sleep modes are controlled by the Power Configuration T7 object settings.
2.7 Haptics Engine
The QT1085 can be configured to play a selected haptic effect in response to a touch detection, a state change on a
GPIO pin or on demand by the host microcontroller.
A selection of haptic effects is available on the device from the Haptic Event T31 object. The effects include:
Strong Click
Strong Click 60% strength
Strong Click 30% strength
Sharp Click
Sharp Click 60% strength
Sharp Click 30% strength
Soft Bump
Soft Bump 60% strength
Soft Bump 30% strength
Double Click
Double Click 60% strength
Triple Click
Soft Buzz
Strong Buzz
Effects may be assigned to events, such as a key touch or GPIO state change.
Refer to the QTAN0085 Haptics Design Guide Application Note and the AT42QT1085 Protocol Guide for more
information on this object.
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3. Wiring and Parts
3.1 Bypass Capacitors
One 100 nF bypass capacitor and one 1 µF bypass c apacitor must be used on the Vdd digital supply and a 100 nF
capacitor on AVDD. The 100 nF capacitors should be mounted close to the device, within 10 mm if possible.
3.2 Rs Series Resistors
Series Rs resistors (Rs0 – RS7) are in-line with the electrode connections and are used to limit electrostatic
discharge (ESD) currents and to suppress radio frequency interference (RFI). For most applications the Rs resistors
will be in the range 4.7 k – 33 k each. For maximum noise rejection the value may be up to 100 k.
Although these resistors may be omitted, the device may become susceptible to external noise or RFI. For details of
how to select these resistors refer to Application Note QTAN0002, Secrets of a Successful QTouch Design.
3.3 Power Supply
See Section 7. on page 19 for the power supply range. If this fluctuates slowly with temperature, the device tracks
and compensates for these changes automatically with only minor changes in sensitivity. If the supply v oltage drifts
or shifts quickly, the drift compensation mechanism will not be able to keep up, causing sensitivity anomalies or false
detections. In this situation a dedicated voltage regulator should be included in the circuit.
The QT1085 power supply should be locally regulated using a three-terminal device. If the supply is s hared with
another electronic system, care should be taken to ensure that the supply is free of digital spikes, sags, and surges,
all of which can cause adverse effects.
3.4 QFN Package Restrictions
The central pad on the underside of the QFN chip should be connected to ground. Do not run any tracks underneath
the body of the chip, only ground. Figure 3-1 on page 8 shows an example of good/bad tracking.
Figure 3-1. Examples of Good and Bad Tracking
Example of GOOD tracking Example of BAD tracking
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3.5 Oscillator
The device has an internal oscillator. No external oscillator or clock input is required.
3.6 PCB Layout and Construction
Refer to Application Note QTAN0079 – Buttons, Sliders and Whee ls Sensor Design Guide and the Touch Sensors
Design Guide (both downloadable from the Atmel website), for more information on construction and design
methods.
The sensing channels used for the individual keys can be implemented as per the Touch Sensors Design Guide.
3.7 PCB Cleanliness
Modern no-clean flux is generally compatible with capacitive sensing circuits.
If a PCB is reworked in any way, clean it thoroughly to remove all traces of the flux residue around the capacitive
sensor components. Dry it thoroughly before any further testing is conducted.
3.8 Spread-spectrum Circuit
The QT1085 spectrally spreads its frequency of operation to heavily reduce susceptibility to external noise sources
and to limit RF emissions.
Bursts operate over a spread of freque ncies, so that external fields will have a minimal effect on key op eration and
emissions are very weak. Spread-spectrum operation works together with th e Detect Integrator (DI) mechanism to
dramatically reduce the probability of false detection due to noise.
Spread spectrum is hardwired in the chip and is automatically enabled.
CAUTION: If a PCB is reworked in any way, it is highly likely that the behavior of the no-clean
flux changes. This can mean that the flux ch anges from an inert material to one that can
absorb moisture and dramatically affect capacitive measurements due to additional leakage
currents. If so, the circuit can become erratic and exhibit poor environmental stability.
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4. Detailed Operation
4.1 Reset
4.1.1 Introduction
When starting from power-up or RESET reset there are a few additional factors to be aware of. In most applications
the host will not need to take special action.
During a reset all outputs are disabled. To define the levels of CHANGE during reset this pin should p ulled up to VDD
with a 10 k to 1M resistor.
When the initial reset phase ends the CHANGE output is enabled. CHANGE drives low.
A software reset may be requested via the Command Processor T6 object.
4.1.2 Delay to SPI Functionality
The QT1085 SPI interface is not operational while the device is being reset. However, SPI is made operational early
in the start-up procedure.
After any reset (either via the RESET pin or via power-up), SPI typically becomes operational within 50 ms of RESET
going high o r power-up. CHANGE is pulled low, and held low until the message server is read by the host micro-
controller, to indicate completion of the initialization sequence after power-on or reset.
4.1.3 Reset Delay to Touch Detection
After power up or reset, the QT1085 calibrates all electrodes.
During this time, touch detection cannot be reported. Calibration completes after 15 burst cycles, which takes
approximately 150 ms, with typical QTouchADC settings.
In total, 200 ms are required from reset or power-up for the device to be fully functional.
4.1.4 Mode Setting After Reset
After a reset the device loads configuration settings from nonvolatile memory, either previously stored or default
settings.
4.2 Calibration
Calibration is the process by which the sensor chip assesses the background capacitance on each channel.
Channels are only calibrated on power-up and when:
The channel is enabled (that is, activated).
OR
The channel is already enabled and one of the following applies:
The channel is held in detect for longer than the Touch Automatic Calibration setting (refer to the
AT42QT1085 Protocol Guide for more information on TCHAUTOCAL setting in the Touch Configuration
T16 object).
Note: This does not apply to a guard channel.
The signal delta on a channel is at least the anti-touch threshold (ATCHCALTHR) in the anti-touch
direction (refer to the AT42QT1085 Protocol Guide for more information on the ATCHCALTHR in the
PROCG_TOUCHCONFIG_T16 object (Touch Configuration T16 object).
The user issues a recalibrate command.
A status message is generated on the start and completion of a calibration.
Note that the device performs a global calibration; that is, all the channels are calibrated together for power-on or
user-requested calibration. Only the individual channel is calibrated for an ATCHCALTHR recalibration.
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4.3 Communications
4.3.1 Introduction
The QT1085 commu nicates as a slave dev ice over a full-duplex 4-wire (MISO, MOSI, SCK, SS) SPI interf ace. In
addition there is a CHANGE pin which is asserted when a message is waiting to be read:
Low = Message waiting
High = No Message waiting
See Section 7.3 on page 19 for details of the SPI Configuration and Timing Parameters.
Figure 7-1 and Figure 7-2 on page 20 show the basic timing for SPI operation. The host does the clocking and
controls the timing of the transfers from the QT1085.
After the host as serts SS low, it should wait >22 µs in low-power mode before starting SCK; in Free run mode, a
delay of 2 µs is sufficient. The QT1085 reads the MOSI pin with each rising edge of SCK, and shifts data out on the
MISO pin on falling edges. The host should do the same to ensure proper operation.
SS must be held low for the duration of a communications exchange (a Read or Write operation). To begin a new
communications exchange, SS must be pulled high for at least 2 ms after a Read or 10 ms after a Write and then
pulled low. SS should be held high when not communicating; if SS is low this is taken as an indication of impending
communications.
In this case, extra current is drawn, as the QT1085 does not enter its lowest power Sleep mode.
All timings not mentioned above should be as in Figure 7-2 on page 20.
4.3.2 CHANGE Pin
The QT1085 has an open-drain CHANGE pin which notifies the host when a message is waiting to be read.
CHANGE is released after each message has been read through an SPI transfer. If further messages are pending,
the QT1085 loads the next one into the Message Handler and then reasserts (pulls low) the CHANGE pin.
4.4 Signal Processing
4.4.1 Power-up Self-calibration
On power-up, or after reset, all channels are typically calibrated and operational within 200 ms.
4.4.2 Drift Compensation
This operates to correct the reference level of each key au tomaticall y over t ime; i t suppresses false detections cau sed
by changes in temperature, humidity, dirt and other environmental effects.
The QT1085 drifts as configured in the Touch Configuration T16 object (refer to the AT42QT1085 Protocol Guide for
more information).
4.4.3 Detection Integrator Filter
The device features a touch detection i ntegration mechanism. This acts t o confirm a detection in a robust fashion. A
counter is increment ed each time a t ouch has exceeded its threshol d and has remained above the threshold f or the
current acquisition. When this counter reaches a preset limit the sensor is finally declared to be touched. If, on any
acquisition, the signal is not seen to exceed the threshold level, the counter is cleared and the process has to start from
the beginning.
The detection integrato r is configured using the touch object Key T13. Refer to the AT42QT10 85 Protocol Guide for
more information.
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4.4.4 Adjacent Key Suppression (AKS) Technology
Adjacent Key Suppre ssion ( AKS) technology i s a patented me thod used to detect which touch obj ect is touched when
objects are located close toge ther. A touch in a group of AKS obj ects is only ind icated on the objec t with the stronges t
touch delta. This is assumed to be the intended object. Once an object in an AKS group is in detect, there can be no
further detections within that group until the object is released.
AKS is configured using the Key T13 object (refer to the AT42QT1085 Protocol Guide for more information).
Note: If a touch is in detect and then AKS is enabled, that touch will not be forced out of detect. It will not go
out of detect until the touch is released. AKS will then operate normally.
4.5 Operating Modes
4.5.1 Introduction
The basic operating modes are: Active, Idle and Sleep.
Cycle time for Idle and Active is set by the Power Configur ation T7 obj ect, with special cases of 255 for free run and 0
for Sleep.
If a touch is detected, the device switches to free run mode and attempts to perform the detect integrator noise filter (DI)
function to completion; if the DI filter fails to confirm a detection the device goes back to Idle mode.
If a key is found to be in detection the part switches to Active mode. If the key is enabled for reporting, a message is
generated and CHANGE is asserted (pulled low).
MISO in LP Mo de:
During the sleep portion of LP mode, MISO floats.
Command During LP Mode:
Once set to Sleep (cycle time = 0), the device carries out no acq uisitions until the cycle
time is changed to >0.
Note: The SS pin must be pulled high in order for the device to enter its lowest power sleep mode. If SS is
held low, the device enters a higher power Sleep mode to enable SPI communications.
4.5.2 Sleep Mode
Sleep mode offers the lowest possible current drain, in the low microamp region. In this mode n o acquisitions are
performed.
In Sleep mode Output GPIOs are held in their final state before going to sleep:
With a 0% PWM the GPIO is Off during sleep
With a 100% PWM the GPIO is On during sleep.
If any other PWM is applied then the state is indeterminate (could be On or Off).
If a haptic effect is playing at the time when Sleep mode is entered, the eff ect is paused and resumed upon exitin g
Sleep mode if the trigger condition remains true.
4.5.3 Supply Sequencing
Vdd and AVdd should be powered by a single supply. Make sure that any lines connected to th e device are below or
equal to Vdd during power-up. For example, if RESET is supplied from a different power domain to the QT1085 Vdd
pin, make sure that it is held low when Vdd is off. If this is not done, the RESET signal could parasitically couple
power via the QT1085 RESET pin into the Vdd supply.
4.6 Debugging
The QT1085 provides a mechanism for obtaining raw data for development and testing purposes by reading data
from the Debug Signals T4 object. Refer to the AT42QT1085 Protocol Guide for more information on this object.
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4.7 Configuring the QT1085
The QT1085 has an object-based protocol that organizes the features of the device into objects that can be
controlled individually. This is configured using the Object Protocol common to many Atmel touch sensor devices.
For more informa tion on the Object Protocol and its implementation on th e QT1085, refer to the AT42QT1085
Protocol Guide. See also Section 6. on page 17.
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5. SPI Protocol for Object Protocol Memory Map Access
5.1 SPI Signals
The Serial Peripheral Interface (SPI) allows high-speed synchronous data transfer between the host and the
QT1085. All communication with the device is carried out over the SPI. This is a synchronous serial data link that
operates in full-duplex mode. The host communicates with the QT1085 over the SPI using a master-slave
relationship, with the QT1085 acting in slave mode.
The SPI uses four logic signals:
Serial Clock (SCK) – output from the host.
Master Output, Slave Input (MOSI) – output from the host, input to the QT1085. Used by the host to send data
to the QT1085.
Master Input, Slave Output (MISO) – input to the host, output from the QT1085. Used by the QT1085 to send
data to the host.
Slave Select (SS) – active low output from the host.
The SPI signals operate in the following way:
SCK Idles high.
MISO and MOSI are set up on falling edges, read on rising edges.
SS must be held low throughout the exchange. SS must be pulled high for at least 2 ms after a Read or 10 ms
after a Write before another exchange can be initiated.
Figure 5-1. SPI Signals
5.2 Communications Protocol
5.2.1 MOSI Data
A 3-byte command sequence is transmitted by the host on MOSI, setting the memory map address pointer, a Read /
Write indication, and the number of bytes which will be read or written.
Read / Write direction is set in Byte 0 Bit 0, where '0' = Write, '1' = Read.
Memory map is addressed in 15 bits, where the lower 7 bits are transmitted at Byte 0, Bits 6 – 1 and the upper 8 bits
at Byte 1.
SAMPLE
MOSI/MISO
CHANGE
MOSI PIN
CHANGE
MISO PIN
SCK
SS
MSB Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 LSB
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5.2.2 MISO Data
Default: 0x55
Returned at each byte on the MISO pin while the 3-byte command sequence is being transmitted on MOSI.
Writing: 0xAA
Returned at each byte on the MISO pin while data is being written by the host on the MOSI pin.
Error: 0xEE
Returned at each byte on the MISO pin in the case where the reques ted number of bytes has be en read or written
but an SS high event has not been detected to begin a new exchange. Or, an attempt has been made to Write to a
read-only part of the memory map, in which case the data written for the remainder of the exchange is ignored.
5.2.3 Write Operation
Table 5-1. MOSI Data
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Byte 0 Memory Map Address, Lower 7 Bits (Bits 6 – 0) 0 = W
Byte 1 Memory Map Address, Upper 8 Bits (Bits 14 – 7)
Byte 2 Number of Data bytes to follow = n
Byte 3 Dat a 0, Written to Memory Map Address
Byte 4 Dat a 1, Written to Memory Map Address + 1
Byte n+3 Data n, Written to Memory Map Address + n
Table 5-2. MISO Data
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Byte 0 0x55
Byte 1 0x55
Byte 2 0x55
Byte 3 0xAA
Byte 4 0xAA
Byte n+3 0xAA
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5.2.4 Read Operation
Table 5-3. MOSI Data
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Byte 0 Memory Map Address, Lower 7 Bits (Bits 6 – 0) 1 = R
Byte 1 Memory Map Address, Upper 8 Bits (Bits 14 – 7)
Byte 2 Number of Data bytes to follow = n
Byte 3 N/A
Byte 4 N/A
Byte n+3 N/A
Table 5-4. MISO Data
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
Byte 0 0x55
Byte 1 0x55
Byte 2 0x55
Byte 3 Data 0, Re ad Fro m Memory Map Address
Byte 4 Data 1, Read From Memory Map Address + 1
Byte n+3 Data n, Read From Memory Map Address + n
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6. Getting Started With the QT1085
6.1 Communication with the Host
The QT1085 uses an SPI bus to communicate with the host. See Section 5. on page 14 for more information.
6.2 Establishing Contact
The host should attempt to read the Information Block information to establish that the device is present and running
following power-up or a reset. The host should also check that there are no configuration errors reported.
6.3 Using the Object Protocol
The QT1085 ha s an object-based prot ocol that is used to co mmunicate with the devic e. Typical communic ation
includes configuring the device, sending commands to the device, and receiving messages from the device. Refer to
the AT42QT1085 Protocol Guide.
The host must perform the following initialization so that it can communicate with the QT1085:
1. Read the start positions and sizes of all the objects in the QT1085 from the Object Table and build up a list of
these addresses.
2. Use the Object Table to calculate the report IDs so that messages from the device can be correctly interpreted.
6.4 Writing to the Device
See Section 5.2.3 on page 15 for information on the format of the SPI Write operation.
To communicate with the QT1085, write to the appropriate object:
To send a command to the device, write the appropriate command to the Command Processor T6 object (for
example, to send a reset, backup or calib rate command). Refer to the AT42QT1085 Protocol Guide for the full
list of available commands.
To configure the device, write to an object. For example, to configure the device power consumption write to
the global Power Configuration T7 object. Some objects are optional and need to be enabled before use.
Refer to the AT42QT1085 Protocol Guide for more information on the objects.
6.5 Reading from the Device
See Section 5.2.4 on page 16 for information on the format of the SPI Read operation.
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6.6 Configuring the Device
The objects are designed such that a default value of zero in their fields is a safe value that typically disables
functionality. The objects must be configured before use and the settings written to the nonvolatile memory using the
Command Processor T6 object. Refer to the AT42QT1085 Protocol Guide for more information.
The following objects must be configured before use:
General Objects
Power Configuration T7
QTouchADC Configuration T49
To uch Objects
Key T13 (8 instances)
Signal Processing Objects
Touch Configuration T16
Support Objects
GPIO Configuration T29 (16 instances)
Haptic Event T31 (8 instances)
Refer to the AT42QT1085 Protocol Guide for information on configuring the objects.
The following objects are also used but require no setting up:
Debug Objects
Debug Deltas T2
Debug References T3
Debug Signals T4
General Objects
Message Processor T5
Command Processor T6
Support Objects
Self Test T25
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7. Specifications
7.1 Absolute Maximum Specifications
7.2 Recommended Operating Conditions
7.3 SPI Bus Specifications
Vdd 2 V – 5.5 V
Max continuous pin current, any control or drive pin 20 mA
Voltage forced onto any pin –0.5 V to (Vdd or AVdd +0.5) V
Configuration parameters maximum Writes 10,000
CAUTION: Stresses beyond those listed under Absolute Maximum Specificatio ns 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
indicate d in the operational sections of this specification is not implied. Exposure to absolute maximum specification
conditions for extended periods may affect device reliabil ity
Operating temp –40°C to +85°C
Storage temp –65°C to +150°C
Vdd 2V – 5.5V
Supply ripple + noise ±20 mV
Cx transverse load capacitance per channel 1 pF to 30 pF
GPO current <5 mA
Temperature slew rate 10°C per minute
See also Figure 5-1 on page 14.
Parameter Specification
Data bits 8 data bits
Data transmission Shift out on falling edge
Shift in on rising edge
Clock idle High
Maximum clock rate 750 kHz
Minimum time between bytes 100 µs
Minimum low clock period 666 ns
Minimum high clock period 666 ns
Delay between communications exch anges 2 ms after Read operation
10 ms after Write operation
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Figure 7-1. Data Byte Exch ange – Signals
Figure 7-2. Data Byte Exch ange – Timings
SAMPLE
MOSI/MISO
CHANGE
MOSI PIN
CHANGE
MISO PIN
SCK
SS
MSB Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 LSB
SS must be held low
between bytes of an
exchange.
Period Min Max Unit
S1 SS Low to SCK – Free-run mode 2 – µs
SS Low to SCK – LP mode 22 –µs
S2 SCK to SS High 20 –µs
S3 SCK Low Pulse 666 –ns
S4 SCK High Pulse 666 –ns
S5 SCK Period 1332 –ns
S6 Between Bytes 100 –µs
S7 SS High to Tristate –20 ns
General Min Max Unit
Rise/Fall T ime –1600 ns
Setup 10 –ns
Hold 333 –ns
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7.4 Reset Timings
7.5 Current Measurements
Parameter Min Typ Max Units Notes
Power on to CHANGE line low –50 –ms
Hardware reset to CHANGE line low –50 –ms
Software reset to CHANGE line low –75 –ms
Keys enabled DP GPIOs 0 to 7
Config 1: 82–1 Output 60% PWM
Config 2: 816–8 Output 60% PWM
Config 3: 82–1 Input
Config 4: 82–1 Off
Config Cycle 5V 3.3 V 2V
Current measurements µA
1a Free run (Actual: 9.1ms) 5380 1890 1025
1b 50 ms 3930 960 585
1c 100 ms 3735 840 500
1d 150 ms 3660 810 473
1e 200 ms 3615 790 455
1f 250 ms 3535 778 448
Config Cycle 5V 3.3 V 2V
Current measurements µA
2a Free run (Actual: 20.3 ms) 5405 1896 1050
2b 50 ms 4250 1205 730
2c 100 ms 3760 950 545
2d 150 ms 3690 890 521
2e 200 ms 3710 855 486
2f 250 ms 3685 832 476
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Config Cycle 5V 3.3 V 2V
Current measurements µA
3a Free run (Actual: 8.6 ms) 6985 1871 1014
3b 50 ms 2280 490 326
3c 100 ms 1380 265 188
3d 150 ms 995 208 142
3e 200 ms 575 150 105
3f 250 ms 421 129 84
Config Cycle 5V 3.3 V 2V
Current measurements µA
4a Free run (Actual: 7.9 ms) 6992 1881 1039
4b 50 ms 2240 450 280
4c 100 ms 1360 268 180
4d 150 ms 1060 204 140
4e 200 ms 568 126 80
4f 250 ms 442 122 78
Config Cycle 5V 3.3 V 2V
Current measurements µA
<0> 21 18 16
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7.6 Mechanical Dimensions
7.6.1 32-pin 5 × 5 mm QFN
$
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7.6.2 32-pin 7 × 7mm TQFP
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7.7 Marking
7.7.1 32-pin 5 × 5 mm QFN
1
32
Pin 1 ID
Date Code Description
W=Week code
Wweek code number 1-52 where:
A=1 B=2 .... Z=26
then using the underscore A=27...Z=52
Date Code
Abbreviation of
part number
AT42QT1085-MU
Code revision
1.0.AA, released
1
32
Pin 1 ID
Abbreviated
part number
Code revision
1.0.AA, released
Chip assembly
datecode
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7.7.2 32-pin 7 × 7mm TQFP
1
32
Pin 1 ID
QT1085
Date Code
YWW= Date programmed
Date Code Description
WW week code number 1-52
Yyear code letter 1-26
AU 1R0
Code revision
1.0.AA, released
Abbreviation of
part number
AT42QT1085-AU
where: A=2001...J=2010 ...Z=2026
Abbreviation of
part number
AT42QT
1085-AU
1
32
Pin 1 ID
Code revision
1.0.AA, released
Chip assembly
datecode
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7.8 Part Numbers
The part number comprises:
AT = Atmel
42 = Touch Business Unit
QT = Charge-transfer technology
1085= (1) Keys (08) number of channels (5) variant number
AU = TQFP chip
MU = QFN chip
R = Tape and reel
7.9 Moisture Sensitivity Level (MSL)
0
Part Number QS Number Description
AT42QT1085-MU QS588 32-pin 5 × 5 mm QFN RoHS compliant
AT42QT1085-MUR QS588 32-pin 5 × 5 mm QFN RoHS compliant – Tape and reel
AT42QT1085-AU QS588 32-pin 7 × 7mm TQFP RoHS compliant
AT42QT1085-AUR QS588 32-pin 7 × 7mm TQFP RoHS compliant – Tape and reel
MSL Rating Peak Body Temperature Specifications
MSL3 260oCIPC/JEDEC J-STD-020
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Associated Documents
Design layout guidelines:
Application Note: QTAN0079 – Buttons, Sliders and Wheels Sensor Design Guide
Haptics guidelines:
Application Note: QTAN0085 – Haptics Design Guide
Miscellaneous:
Application Note: QTAN0015 – Power Supply Considerations for QT ICs
Application Note: Atmel AVR3000: QTouch Conducted Immunity
Design Guide: QTAN0087 – Proximity Design Guide
Revision History
Revision Number History
Revision AX – May 2011 Initial release for firmware version 0.4
Revision BX – August 2011 Firmware version 0.5
Amendments and clarifications to text.
Revision C – December 2011 Firmware version 1.0.AA
Amendments and clarifications to text.
Revision D – May 2013 Amendments and clarifications to text
New template and package mechanical drawings
Changed package designation from MLF to QFN
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