ASF - Atmel QTouch with XMEGA USB HID - Atmel Corporation

APPLICATION NOTE 

Atmel AVR1632: ASF – Atmel QTouch with XMEGA USB 

HID 

Features 

8-bit Atmel Microcontrollers 

• Single-Chip solution 

• Atmel ® QTouch ® and USB HID on Atmel AVR ® ATxmega256A3BU 

• Using QTouch Library 4.4 

• Using Atmel Studio 6 

• Simple PC interface with Read/Write functions 

• Remote wake up and USB bus powered support 

Introduction 

This application note describes how to use the QTouch library with the 

ATxmega256A3BU microcontroller using QTouch button available on XMEGA-A3BU 

Xplained board. QTouch sensor status is acquired and reported over the USB HID 

class to a host PC. It provides a single chip solution for sensing QTouch through USB 

interface. 

USB interface 

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Table of Contents 

1. Glossary ............................................................................................... 3 

2. Overview .............................................................................................. 3 

3. Quick start ............................................................................................ 4 

3.2 User interface .................................................................................................... 5 

4. Building a USB device HID Generic with QTouch................................ 5 

4.1 Importing and configuring USB module ............................................................. 5 

4.2 QTouch Library Integration ............................................................................... 6 

5. Project options ..................................................................................... 7 

5.1 Compiler and assembler options ....................................................................... 7 

5.2 Linker options .................................................................................................... 9 

6. Example firmware ................................................................................ 9 

6.1 QTouch interface file – touch.c.......................................................................... 9 

6.1.1 QTouch initialization............................................................................ 9 

6.1.1.1 config_sensor .................................................................... 9 

6.1.1.2 qt_init_sensing ................................................................ 10 

6.1.1.3 qt_set_parameters .......................................................... 10 

6.1.1.4 init_timer_isr .................................................................... 10 

6.1.2 Timer interrupt callback ..................................................................... 10 

6.1.3 Check key press ............................................................................... 10 

6.2 Example behavior ........................................................................................... 11 

6.2.1 ui_process ........................................................................................ 11 

7. Host application ................................................................................. 12 

8. Recommended reading ...................................................................... 13 

Atmel AVR1632: ASF – Atmel QTouch with XMEGA USB HID [APPLICATION NOTE] 

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1. Glossary 

ASF 

HID 

UDC 

UDD 

UDI 

USB 

Atmel Studio 6 

Atmel QTouch Library 

Atmel Software Framework 

Human Interface Device 

USB Device Controller 

USB Device Descriptor 

USB Device Interface 

Universal Serial Bus 

Integrated Development Environment (IDE) for Atmel AVR applications 

Software library for touch applications on Atmel AT91SAM and AVR microcontrollers 

XMEGA-A3BU Xplained Evaluation Kit for the Atmel ATxmega256A3BU 

2. Overview 

This demo application acquires the change in QTouch key status (ON/OFF), generates the report, and sends it to a host 

(PC) on request. This application is built over the generic USB HID application which allows simple data exchange 

between host and the device. The host peridiocally requests for change in QTouch key status. The device will send 

changed status if available, otherwise it will send a NAK (No Acknowledge) to tell the host that there is no change in the 

key status. The data packet sent from the device to the host is called report IN. 

Figure 2-1. Application overview. 

USB + QTouch Application 

QTouch Library 

UDC 

UDI – HID 

Generic 

UDI – HID 

UDD 

USB Device stack from the ASF 

The report sent to the host contains a set of bytes which can be used by the user application to transfer data depending 

on the requirement. Because this application transfers the status of one button at a time, one bit in a byte is sufficient to 

transfer the button status. The least significant byte (LSB) of the report byte has the value of the button status. This can 

be modified depending on the requirement. 


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Table 2-1. 

Push buttons and QTouch button mapping on XMEGA-A3BU Xplained. 

Button 

Push button SW0 



QTouch button QTB0 

Pin mapping 

PE5 

PF1 

PF2 

PF6 -> SNS, PF7 -> SNSK 

3. Quick start 

USB device generic HID example with QTouch for XMEGA-A3BU Xplained is available in Atmel Studio 6. 

Atmel Studio 6 allows the creation of a New Example Project. In the examples list, select a USB QTouch Device HID 

Generic Example. 

The project does not require any modification and only needs to be built, loaded, and run. 

Figure 3-1. New example from Atmel Studio. 


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3.2 User interface 

The user interface consists of switches and LEDs. The resources used from XMEGA-A3BU Xplained board for this 

example are: 

• Two user LEDs – LED2 and LED3 

• One QTouch button QTB0 

• Three push buttons SW0, SW1 and SW2 

• LED0 is ON when USB line is in IDLE mode, and OFF in SUSPEND mode 

• LED1 blinks when USB Host has checked and enabled HID generic interface 

User LEDs 

Figure 3-2. XMEGA – A3BU Xplained. 

LED0 

Push buttons 

LED1 

QTouch 

button 

4. Building a USB device HID Generic with QTouch 

The USB device HID Generic modules provide a USB HID Generic interface which can be used to build a USB 

application. These modules are available in Atmel Studio 6 and can be imported in an Atmel Studio 6 Project. To this, 

QTouch library should be added and configured. 

4.1 Importing and configuring USB module 

The USB device HID Generic modules can be added from the ASF wizard in Atmel Studio 6. Once these modules are 

added, it is necessary to configure them as per the application needs. 

The configuration details are illustrated in Atmel AVR4905: ASF – USB Device HID Generic Application: 

http://www.atmel.com/Images/doc8499.pdf [4] . 


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4.2 QTouch Library Integration 

To build the application, the appropriate QTouch header files, assembler files and library files (which are device and 

compiler specific) need to be integrated with other source files. To select the correct device and the application-specific 

library files, refer to the Library_Selection_Guide.xls file in the QTouch library [2] available for download on Atmel 

website. The following should be options should be set for selecting the QTouch library for ATxmega256A3BU. 

Table 4-1. 

Options to be set for selecting QTouch Library for ATxmega256A3BU. 

Option 

Value 

Technology 

QTouch 

MCU Family Atmel AVR XMEGA ® 

MCU Type 

8-bit 

MCU 

ATxmega256A3BU 

Ports available for QTouch 

A, B, C, D, E, F 

Maximum number of channels 4 

Maximum number of rotors 0 

Toolchain 

GCC 

By selecting these parameters, the appropriate library files to be included can be seen. 

• libavrxmega6g1-4qt-k-0rs.a – GCC library file for the respective device 

• qt_asm_xmega.S – assembler file 

• touch_qt_config.h 

• touch_api.h 


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Figure 4-1. Library Selection Guide. 

5. Project options 

5.1 Compiler and assembler options 

For the QTouch application, certain options should be set in the compiler and assembler. In GCC, open Project Options 

-> Toolchain -> AVR/GNU C Compiler -> Symbols. Add the following to Defined symbols one by one in Atmel Studio 6 

(Figure 5-1). 

_QTOUCH_ 

SNS1=F 

SNSK1=F 

_SNS1_SNSK1_SAME_PORT_ 

QT_DELAY_CYCLES=1 

QT_NUM_CHANNELS=4 

QTOUCH_STUDIO_MASKS=1 

NUMBER_OF_PORTS=1 


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Figure 5-1. GCC compiler options. 

Add Symbols 

The above options have to be set in the assembler as well, as shown in Figure 5-2. 

Figure 5-2. GCC assembler options. 

Add here 


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5.2 Linker options 

In GCC, open Project Options -> Toolchain -> AVR/GNU C Linker -> Libraries. Add the following library (Figure 5-3) 

avrxmega6g1-4qt-k-0rs 

Also specify the path where the library is located. 

Figure 5-3. Linker options. 

Add library 

Add library path 

6. Example firmware 

This document explains only the QTouch interface file and example behavior. Description about USB Device HID 

Generic is available in Atmel AVR4905: ASF – USB Device HID Generic Application: 

http://www.atmel.com/Images/doc8499.pdf. 

6.1 QTouch interface file – touch.c 

6.1.1 QTouch initialization 

The touch_init function is responsible for calling the initialization routines related to QTouch sensing. 

config_sensor(); 

qt_init_sensing(); 

qt_set_parameters(); 

init_timer_isr(); 

Each of the functions are described in the following sections. 

6.1.1.1 config_sensor 

The config_sensor function is responsible for configuring the sensors as keys and assigning the channel numbers. 


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channel_t 

qt_enable_key(CHANNEL_0, NO_AKS_GROUP, 10, HYST_6_25); 

– channel number to be configured for a key 

aks_group_t – Adjacent Key Suppression ® (AKS ® ) group associated with the sensor being configured as “key” 

threshold_t – Detect threshold for the sensor 

hysteresis_t – Detection hysteresis for the sensor 

Refer to the Atmel AVR QTouch Library User Guide: 

http://www.atmel.com/dyn/resources/prod_documents/doc8207.pdf for more information on this function. 

6.1.1.2 qt_init_sensing 

The qt_init_sensing function is used to initialize the QTouch sensing for all enabled channels. All required sensors 

should be configured before calling this function. 

#define qt_init_sensing( ) qt_init_sensing_with_burst( BURST_FUNC_NAME ,CALCULATE_MASKS) 

6.1.1.3 qt_set_parameters 

The qt_set_parameters function is used to initialize the global configuration settings in the variable qt_config_data of the 

QTouch acquisition method libraries. In other words, this will fill the default threshold values in the configuration data 

structure. 

6.1.1.4 init_timer_isr 

The example uses TC driver from ASF. It enables the timer, sets the timer period, clock source, interrupt level and 

interrupt callback functions. The timer period defines the time interval between consecutive QTouch measurements. 

6.1.2 Timer interrupt callback 

Sets the flag time_to_measure_touch and updates the current time that is used by the QTouch Library. 

6.1.3 Check key press 

The check_touch_key_pressed function in the QTouch interface file (touch.c) from example is responsible for 

measuring the QTouch sensing and reporting the key status. 

uint16_t status_flag; 

uint16_t burst_flag; 

#ifdef _DEBUG_INTERFACE_ 

/* Process commands from PC */ 

#endif 

QDebug_ProcessCommands(); 

if (time_to_measure_touch) 

{ 

time_to_measure_touch = false; 

do { 

status_flag = qt_measure_sensors( current_time_ms_touch ); 

burst_flag = status_flag & QTLIB_BURST_AGAIN; 


QDebug_SendData(status_flag); 


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#endif 

/* Time-critical host application code should be placed here since 

* a full burst cycle may delay critical task in the main application 

*/ 

}while (burst_flag) ; 


/* Process commands from PC */ 

QDebug_ProcessCommands(); 

#endif 

} 

if(GET_SENSOR_STATE(0)) 

return 0; 

else 

return 1; 

6.2 Example behavior 

6.2.1 ui_process 

The main.c and ui.c implement the user interface for Atmel QTouch demonstration with Atmel XMEGA USB HID 

application. 

The implementation is comprised of three steps: 

1. Start the USB Device 

udc_start(); 

udc_attach(); // Must be called when the USB cable is plugged 

// Cable plugged is detected via VBUS events 

2. Wait for the HID Generic interface to be enabled via a callback 

UDI_HID_GENERIC_ENABLE_EXT() // Authorize the Generic HID events 

3. Scan the buttons and send the status 

b_btn_state = (!check_touch_key_pressed()) ? true : false; 

if (b_btn_state != btnq_last_state) { 

ui_hid_report[0]=b_btn_state; 

udi_hid_generic_send_report_in(ui_hid_report); 

btnq_last_state = b_btn_state; 

} 

Note: 

To simplify the USB implementation, the SOF event is used to scan switches every 1ms. 

More description on how Generic HID example works is available in the application note Atmel AVR4905: ASF – USB 

Device HID Generic Application: http://www.atmel.com/Images/doc8499.pdf. 


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7. Host application 

Atmel PC tool allows communicating with the generic HID device. The PC tool is available with Application 

Note AVR153: USB PC Drivers Based on Generic HID Class: 

http://www.atmel.com/dyn/resources/prod_documents/doc7645.pdf AVR153 – USB PC Drivers Based on Generic HID 

Class as AVR153.zip [6]. Whenever there is a key press and release, it updates in the display of PC Tool. The key 

press or release is displayed as shown in Figure 7-1. 

Use the LED2 ON/OFF and LED3 ON/OFF buttons to turn ON and OFF the LED2 and 3. Push and release the buttons 

SW0, SW1, SW2 and QTouch button QTB0 to see the status displayed on the PC application window. 

Information on integrating the Atmel USB HID DLL functions and simple code examples that demonstrate different types 

of implementation are available in the document “USB PC Drivers Based on Generic HID Class” [6]. 

Figure 7-1. Ket status. 

Note: 

Caution: 

Use the PID 0x2402 in the graphic tool interface. 

The button ‘Firmware Upgrade’ only disconnects the USB device. 


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8. Recommended reading 

[1] Atmel XMEGA AU Manual: http://atmel.com/dyn/resources/prod_documents/doc8331.pdf 

[2] Atmel QTouch Library 4.4: http://www.atmel.com/tools/QTOUCHSTUDIO4_3_1.aspx 

[3] Atmel AVR QTouch Library User 

Guide: http://www.atmel.com/dyn/resources/prod_documents/doc8207.pdf 

[4] Atmel AVR4905: ASF – USB Device HID Generic Application: http://www.atmel.com/Images/doc8499.pdf 

[5] ASF Documentation: http://asf.atmel.com/docs/latest/ 

[6] AVR153: USB PC Drivers Based on Generic HID 

Class: http://www.atmel.com/dyn/resources/prod_documents/doc7645.pdf 

[7] AVR1923: XMEGA-A3BU Xplained Hardware User 

Guide: http://atmel.com/dyn/resources/prod_documents/doc8394.pdf 

[8] AVR1934: XMEGA A3BU Xplained Software User 


[9] AVR1935: XMEGA A3BU Xplained Getting Started 



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ASF - Atmel QTouch with XMEGA USB HID - Atmel Corporation

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