ATAVRQTOUCHX Atmel, ATAVRQTOUCHX Datasheet - Page 46

• Manufacturer Part Number: ATAVRQTOUCHX
• Description: BOARD EVAL CAPACITIVE TOUCH
• Manufacturer: Atmel
• Series: QTouch™r

Specifications of ATAVRQTOUCHX

• Sensor Type: Touch, Capacitive
• Sensing Range: 1 Slider, 1 Wheel, 2 Buttons
• Interface: USB
• Voltage - Supply: 5V, USB
• Embedded: Yes, MCU, 8-Bit
• Utilized Ic / Part: AT90USB1287, ATxmega128A1
• Silicon Manufacturer: Atmel
• Silicon Family Name: ATxmega
• Kit Contents: Board
• Svhc: No SVHC (15-Dec-2010)
• Core Architecture: AVR
• Core Sub-architecture: AVR19
• Kit Features: One Slider, One Wheel And 2
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Sensitivity: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Example:
When operating at 4 MHz, 1~10 cycle charge times are recommended (0.125us to 1.25us).
Note:
If the microcontroller is only used for Touch detection then running at the lowest frequency
possible for the desired touch response may provide the best power and EMC performance. If it
is also used for other functions then running at a higher frequency may be necessary. In some
power critical applications it may be worth switching the frequency on the fly, such as lowering the
frequency during touch detect API instead of using long cycle times, and then switching to a
higher frequency for non-touch code. It is necessary to carefully design timer operation when
change frequencies.
5.6.9
The library disables interrupts for time-critical periods during touch sensing. These periods are
generally only a few cycles long, and so host application interrupts should remain responsive
during touch sensing. However, any interrupt service routines (ISRs) during touch sensing should
be as short as possible to avoid affecting the touch measurements or the application
responsiveness. As a rule of thumb, the combined durations of any ISRs during a capacitive
measurement should be less than 1 msec,i.e., the QTouch acquisition cannot be pre-empted for
more than 1msec. This can be tested during system development by checking the acquisition
duration on the touch channels on an oscilloscope. If the total burst duration for any channel
varies by more than 1ms while the user is not touching any sensors, then ISRs could adversely
affect the measurements. Please note that none of the API functions should be called from a user
interrupt.
5.6.10 Integrating QTouch libraries in your application
This section illustrates the key steps required in integrating the QTouch library in your application.
5.6.10.1 Directory structure of the library files
The QTouch library directory structure is as listed below
What
Root
installation
Header file
46
•
For UC3 and ATSAM devices, 1 & 2 charge cycle delay times are not supported.
Interrupts
Microcontroller
Frequency of
Where
Default directory is
C:\Program
Files\Atmel\Atmel_QTouch_Libraries_4.x\Generic_QTouch_Libraries
..\include
(MHz))
>48
10
16
20
48
1
2
4
8
microcontroller Cycle time
(us)
Table 2 : Frequency of operation
<0.02083
0.02083
0.0625
0.125
0.25
0.05
0.5
0.1
1
Suitable Charge Cycle times (or)
Suitable Dwell Cycle times
(us)
1 to 2 cycles (1us to 2us)
1 to 5 cycles (0.5us to 2.5us)
1 to 10 cycles (0.25us to 2.5us)
1 to 10 cycles (0.125us to 1.25us)
2 to 25 cycles (0.2us to 2.5us)
2 to 25 cycles (0.125us to 1.5625us)
3 to 50 cycles (0.15us to 2.5us)
5~50 cycles (0.104us to 1.04us)
5 to < 50 (up to 255 cycles for 8bit AVR)
8207J-AT42-02/11
Comments
This
directory path but the user
can install the directory in
desired location.
touch_api.h is located in
is
the
default