XC83x AP08127 Microcontrollers Application Note - Infineon

XC83x AP08127 inTouch Application Kit - Touch Buttons

Application Note V1.0, 2012-02

Microcontrollers

Edition 2012-02 Published by Infineon Technologies AG 81726 Munich, Germany © 2012 Infineon Technologies AG All Rights Reserved. LEGAL DISCLAIMER THE INFORMATION GIVEN IN THIS APPLICATION NOTE IS GIVEN AS A HINT FOR THE IMPLEMENTATION OF THE INFINEON TECHNOLOGIES COMPONENT ONLY AND SHALL NOT BE REGARDED AS ANY DESCRIPTION OR WARRANTY OF A CERTAIN FUNCTIONALITY, CONDITION OR QUALITY OF THE INFINEON TECHNOLOGIES COMPONENT. THE RECIPIENT OF THIS APPLICATION NOTE MUST VERIFY ANY FUNCTION DESCRIBED HEREIN IN THE REAL APPLICATION. INFINEON TECHNOLOGIES HEREBY DISCLAIMS ANY AND ALL WARRANTIES AND LIABILITIES OF ANY KIND (INCLUDING WITHOUT LIMITATION WARRANTIES OF NON-INFRINGEMENT OF INTELLECTUAL PROPERTY RIGHTS OF ANY THIRD PARTY) WITH RESPECT TO ANY AND ALL INFORMATION GIVEN IN THIS APPLICATION NOTE. Information For further information on technology, delivery terms and conditions and prices, please contact the nearest Infineon Technologies Office (www.infineon.com). Warnings Due to technical requirements, components may contain dangerous substances. For information on the types in question, please contact the nearest Infineon Technologies Office. Infineon Technologies components may be used in life-support devices or systems only with the express written approval of Infineon Technologies, if a failure of such components can reasonably be expected to cause the failure of that life-support device or system or to affect the safety or effectiveness of that device or system. Life support devices or systems are intended to be implanted in the human body or to support and/or maintain and sustain and/or protect human life. If they fail, it is reasonable to assume that the health of the user or other persons may be endangered.

AP08127 inTouch Application Kit - Touch Buttons

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AP08127 inTouch Application Kit - Touch Buttons

Table of Contents 1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2 2.1 2.2

Hardware and Program Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Hardware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Program Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3

Behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

4 4.1

U-SPY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 inTouch_Buttons.ini . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Appendix - Schematics and Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

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AP08127 inTouch Application Kit - Touch Buttons Introduction

1

Introduction

In today's Human-Machine Interface (HMI) designs, capacitive touch technology is now often more widely used than traditional mechanical buttons. Capacitive touch technology is the more popular choice because it brings flexibility, a high-level of customization, and a significant reduction in overall system cost. The inTouch Application Kit is available to help learn about working with the advanced touch solutions provided by Infineon. Step-by-step tutorials covers the basics of Infineon's touch solutions, while example application code can be used to start developing new touch-related projects. The inTouch Application Kit comprises of a mother board, supplied as a USB stick, and a number of daughter boards. Figure 1 shows the buttons daughter board. Among the many different touch input elements that can be designed with capacitive touch technology, the single pad button is probably the simplest and most popular. This application note describing the buttons daughter board, aims to highlight the ease of implementing a design with Infineon's touch solutions. Topics covered include program flow and touch behavior.

Figure 1

inTouch Application Kit (USB Stick and Buttons board)

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AP08127 inTouch Application Kit - Touch Buttons Hardware and Program Flow

2

Hardware and Program Flow

This section describes the hardware used and the connections involved.

2.1

Hardware

Infineon’s XC836MT 2FRI (Figure 2) is used in this application. The XC836MT is embedded in the inTouch Application Kit’s USB stick. For more details regarding the USB stick, please refer to AP08126: Infineon Touch Solutions - inTouch Application Kit.

Figure 2

Infineon’s XC836MT 2FRI

The inTouch Buttons board (Figure 3) is available as a plug-in daughter board which is part of the inTouch Application Kit.

Figure 3

Buttons daughter board

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AP08127 inTouch Application Kit - Touch Buttons Hardware and Program Flow The inTouch Buttons board is a standard PCB with a piece of 2mm-thick plexiglas glued on top of the board. The buttons on the top row are each connected to an ADC input channel of the XC836. The buttons in the bottom row are each connected to an LEDTS input pin of the XC836. 14 indicator LEDs are connected to 2 LED column pins (1 for each row) and 7 LED line pins of the XC836. The schematics are available in the Appendix - Schematics and Layout. Users can touch-and-hold (default) or tap the 14 buttons to toggle the indicator LEDs depending on the downloaded software.

2.2

Program Flow

Infineon offers 3 solutions for capacitive touch sensing. The bottom 7 buttons, which are connected to LEDTS input pins and hence controlled by the LEDTS module of the XC836, use the Relaxation Oscillator Topology for touch sensing. The top 7 buttons, which are connected to ADC input pins, can use either the Charge Redistribution (CR) or the Charge-Time Measurement (CTM) methods for touch sensing. Because two options are available, the program name in the program flow description is taken from the name of the method (CR or CTM) used for the top 7 buttons. For more information on the 3 touch solutions, refer to the application note AP08126: inTouch Application Kit USB Stick. In terms of interrupts, UART interrupt has a medium priority because of the high data rate. Touch sense related tasks are also performed with medium priority. These occur in the Time Frame interrupt after pad capacitances have been measured. LED updates have the lowest priority. These are performed in the Time Slice interrupt together with pad capacitance measurement. These apply to both CR (Figure 4) and CTM (Figure 5) methods. In the CTM method, the ADC interrupt is enabled and this has the highest priority to facilitate accurate charge time measurement.

low

Figure 4

TIME SLICE INTERRUPT every 384μs

medium

TIME FRAME INTERRUPT every 1.152ms

medium

UART INTERRUPT

LED settings, ADC pads capacitance measurement

Touch Sense signal processing

Communication with PC (send data & receive commands)

RETI

RETI

RETI

Program Overview - CR Method

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AP08127 inTouch Application Kit - Touch Buttons Hardware and Program Flow

low

Figure 5

TIME SLICE INTERRUPT every 416μs

medium

TIME FRAME INTERRUPT every 1.248ms

medium

UART INTERRUPT

high

ADC INTERRUPT

LED settings ADC pads capacitance measurement

Touch Sense signal processing

Communication with PC (send & receive data)

Retrieve conversion time

RETI

RETI

RETI

RETI

Program Overview - CTM Method

The tasks performed in each interrupt service routines are further illustrated in the flowcharts which follow: •

•

•

•

UART Interrupt (Figure 6) – The UART module, which is part of the XC800 core, is used for full-duplex UART communication with the PC. Time Slice Interrupt (Figure 7) – The LEDTS module generates this interrupt after every LED column activation where the pattern for the next LED column is loaded into shadow registers. Time Frame Interrupt (Figure 8) – The LEDTS module generates this interrupt after every measurement where signal processing and touch detection take place. ADC Interrupt (Figure 9) – The ADC generates this interrupt after the pad has been charged to the defined level, so that the chargetime can be measured.

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AP08127 inTouch Application Kit - Touch Buttons Hardware and Program Flow

Start

Receiver Interrupt?

New command?

Yes

Yes

Retrieve data from buffer

No

No

Check button selected

Transmitter Interrupt?

Yes

Shift data out to buffer

No RETI

Figure 6

UART Interrupt Service Routine

Start

Figure 7

Set LED LINE and COMPARE values

Measure ADC pad capacitance

RETI

Time Slice Interrupt Service Routine

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AP08127 inTouch Application Kit - Touch Buttons Hardware and Program Flow

Start

RETI

LEDTS pads signal processing ADC pads signal processing

Toggle LED

No

Reverse bits of ADC pad flags

Blink LEDs

PADRESULT set?

No

Yes

LED blinking?

Yes

Blink LED

No

Off all LEDs

Yes

Send LED status to USpy

Yes

Off LED

No

Startup over?

No

Self-calibration

PADERROR set?

Yes

Oscilloscope mode?

Figure 8

Yes

Yes

Send pad Total_TSCTR & pad Average to USpy

No

No

Do adaptive calibration

LED Status mode?

Time Frame Interrupt Service Routine

Start

Figure 9

Offline mode?

Clear Interrupt Flag

Stop Timer 2

RETI

ADC Interrupt Service Routine (CTM Method)

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AP08127 inTouch Application Kit - Touch Buttons Behavior

3

Behavior

The inTouch Buttons board has 4 software versions: 1. The LEDs light up when respective pads are touched, using the CR method for the ADC touch pads (this is the default software). 2. LEDs toggle when respective pads are tapped, using the CR method for the ADC touch pads. 3. The LEDs light up when respective pads are touched, using the CTM method for the ADC touch pads. 4. LEDs toggle when respective pads are tapped, using the CTM method for the ADC touch pads. Software versions 1 and 3 use the PADFLAG output of the LEDTS ROM Library and the PADTOUCHED output of the ADC Touch Library to implement the touch behavior as described above. Software versions 2 and 4 use the PADRESULT outputs of the LEDTS ROM Library and the ADC Touch Library to implement the touch behavior described above. All software versions use the PADERROR output of the LEDTS ROM Library and the ADC Touch Library to blink the LEDs when there is a long touch on the buttons.

4

U-SPY

For the inTouch Buttons board, one settings file, inTouch_Buttons.ini, has been configured.

4.1

inTouch_Buttons.ini

This settings file (Figure 10) is customized to allow the user to monitor the parameters of the LEDTS ROM Library and the ADC Touch Library.

Buttons

Status Flags

Figure 10

inTouch_Buttons.ini User Interface

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AP08127 inTouch Application Kit - Touch Buttons U-SPY Buttons In this settings file, the buttons allow the user to choose the signal which the user would like to monitor. The description of the data format for the buttons is the same as in the previous settings file. Data is transmitted in the following format (Table 1): Table 1

Transmit Data Format for Buttons D0

D1

Value (hex)

08

XX

Description

I.D. number

Button number

The data received by the microcontroller will be used to determine the signals that will be transmitted to U-SPY for display either as Status Flags (if LED Status button is selected) or on the Oscilloscope (if TSPADx or ADCPADx is selected). If OFFLINE is selected, the microcontroller will stop sending data to U-SPY, and all touches will be indicated by the LEDs on the board. Status Flags The format of the transmitted data for the status flags is as follows (Table 2): Table 2

Transmit Data Format for Status Flags D0

D1

D2

Value (hex)

A3

30/31

XX

Description

I.D. number

TSLED - 30 ADCLED - 31

Mask

The statuses of the LEDs received by USpy are masked before they are displayed as status flags. It is important that the bits of a mask do not overlap with the bits of another mask. This is to ensure that status flags are not falsely turned on. The masks used are as follows (Table 3): Table 3

LED masks for Status Flags

LED Number

1

2

3

4

5

6

7

Mask (hex)

01

02

04

08

10

20

40

Oscilloscope The oscilloscope function allows the user to monitor up to 3 signals per oscilloscope at a time (Figure 11). A total of 3 oscilloscopes are available. However, we will display only 2 signals on 1 oscilloscope in this application. The format of the transmitted data for the oscilloscope is as follows (Table 4):

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AP08127 inTouch Application Kit - Touch Buttons U-SPY

Figure 11

U-SPY Oscilloscope

Table 4

Transmit Data Format for Oscilloscope D0

D1

D2

D3

D4

D5

D6

D7

Value (hex)

A4

01

XX

XX

XX

XX

XX

XX

Description

I.D. number

Scope number

Signal 1 high byte

Signal 1 low byte

Signal 2 high byte

Signal 2 low byte

-

-

The signals displayed are as follows (Table 5): Table 5

Signals Displayed on Oscilloscope

Description Colour

Application Note

Signal 1

Signal 2

Pad Average

Pad Total_TSCTR * 2DIVISORN

Green

Pink

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Application Note Figure 12

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inTouch Buttons Board Schematics D

C

B

A TP1

P$1

P$1

PAD_ROUND-15.0MM TP2

1

P$1

1

P$1

PAD_ROUND-15.0MM TP3

P$1

P$1

PAD_ROUND-15.0MM

18

20

16

14

12

8

6

4

2

10

TP4

P$1

P$1

AN1

AN0

AN3

AN2

AN5

AN4

AN6

2

COL1

COL2

COL0

LINE6

LINE5

LINE4

LINE3

COL5 LINE2

2

COL4 LINE1

COL3 LINE0

PAD_ROUND-15.0MM TP5

P$1

P$1

19

17

15

13

11

9

7

5

3

1

PAD_ROUND-15.0MM TP6

GND

P$1

P$1

PAD_ROUND-15.0MM TP7

P$1

P$1

3

R7 1k5

R6 1k5

R5 1k5

R4 1k5

R3 1k5

R2 1k5

R1 1k5

3

PAD_ROUND-15.0MM

LED1 green

TP8

P$1

LED2 green

P$1

PAD_ROUND-15.0MM TP9

LED3 green

P$1

P$1

PAD_ROUND-15.0MM

4

4

LED4 green

TP10

P$1

LED5 green

P$1

PAD_ROUND-15.0MM

P$1

P$1

PAD_ROUND-15.0MM TP12

P$1

5

5

Touch Buttons

Touch Sense Application Kit

TP11

LED6 green LED7 green

P$1

LED8 green

PAD_ROUND-15.0MM TP13

LED9 green

P$1

P$1

PAD_ROUND-15.0MM

LED10 green

TP14

P$1

LED11 green

P$1

PAD_ROUND-15.0MM

6

6

LED12 green LED13 green LED14 green

D

C

B

A

Appendix - Schematics and Layout Appendix - Schematics and Layout

AP08127 inTouch Application Kit - Touch Buttons

AP08127 inTouch Application Kit - Touch Buttons Appendix - Schematics and Layout

15

7R

Application Note

8DEL

inTouch Buttons Board Top Layout

6R

5R

Figure 14

1DEL

9DEL

01DEL

21DEL

31DEL

41DEL

inTouch Buttons Board Component Bottom Layout

2DEL

3DEL

5DEL

6DEL

7DEL

Figure 13

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AP08127 inTouch Application Kit - Touch Buttons Appendix - Schematics and Layout

Figure 15

inTouch Buttons Board Bottom Layout

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AP08127 inTouch Application Kit - Touch Buttons References

References The list below provides resources that may be useful to the user. 1. 2. 3. 4. 5. 6. 7. 8.

User’s Manual - XC83x; 8-Bit Single-Chip Microcontroller Application Note - AP08100 - Configuration for Capacitive Touch-Sense Application Application Note - AP08110 - Design Guidelines for XC82x and XC83x Board Layout Application Note - AP08113 - Capacitive-Touch Color Wheel Implementation Application Note - AP08115 - Design Guidelines for Capacitive Touch-Sensing Application Application Note - AP08121 - Infrared Remote Controller with Capacitive Touch Interface Application Note - AP08122 - 16-Button Capacitive Touch Interface with XC836T Application Note - AP08124 - XC82/83x Design Guidelines for Electrical Fast Transient (EFT) Protection in Touch-Sense Applications 9. Application Note - AP08126 - Infineon Touch Solutions - inTouch Application Kit 10. Application Note - AP08128 - inTouch Application Kit - Touch Wheel 11. Application Note - AP08129 - inTouch Application Kit - Touch Sliders 12. Application Note - AP08130 - inTouch Application Kit - LED Matrix 13. Link to XC83x-Series - www.infineon.com/xc83x 14. Link to Solutions for advanced touch control - www.infineon.com/intouch

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