Infineon XC800 AP08113 Installation and operating instructions

XC800 Family

AP08113

Capacitive-Touch Color Wheel Implementation

Microcontrollers

Application Note

V1.0, 2010-08

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Edition 2010-08

Published by

Infineon Technologies AG

81726 Munich, Germany

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Application Note 3 V1.0, 2010-08

AP08113

Capacitive-Touch Color Wheel Implementation

XC822T

Revision History: V1.0 2010-08

Previous Version(s):

Page Subjects (major changes since last revision)

– This is the first release …

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AP08113

Capacitive-Touch Color Wheel Implementation

Table of Contents

Application Note 4 V1.0, 2010-08

Table of Contents

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

1.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2 Color Wheel Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

3 Implementation of Color Wheel Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3.1 Touch Detection Methodology (using Touch-Wheel and LEDTS ROM Library) . . . . . . . . . . . . . . . . . . 7

3.1.1 Touch Detection Methodology for the Centre Button . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

3.1.2 Touch Detection Methodology for the Touch-Wheel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

3.2 Touch-Wheel Library . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3.2.1 Calc_Touchwheel() Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3.2.2 Calc_Compensation() Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3.3 RGB LED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3.4 Overview Flow Chart of Color Wheel Software Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

4 Modifying Color Wheel Software Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

4.1 User-Defined Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

4.2 DAvE-Bench Tool . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

5 Downloading Modified Color Wheel Software Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

5.1 Access Code to UART BSL Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

6 Implementation of Color Wheel with XC822T . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

6.1 Real-Time Clock (RTC) Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

6.2 Power Saving Control Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

6.3 CCU6 Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

6.4 Interrupt System Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

6.5 UART Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

6.6 LED and Touch-Sense Controller Unit Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

7 Schematics and Layout of the Color Wheel Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

8 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

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AP08113

Capacitive-Touch Color Wheel Implementation

Introduction

Application Note 5 V1.0, 2010-08

1 Introduction

This application note describes the Color Wheel Application Kit, a ready-to-use implementation of the touch-

sensing application to adjust light colors with a touch-wheel (Figure 1). The kit is built around the XC822T, a

member of Infineon Technologies 8-bit microcontrollers XC800 Family, which is capable of capacitive touch

detection and LED driving with color control.

The implementation comprises of a touch-wheel PCB board consisting of XC822T, the LEDs and the software

code running on XC822T. This document takes the user through the steps necessary to create their own XC822T1)

solution. The source code provided can be modified and compiled with the free DAvE-Bench tool chain. The user

can download the code into flash, execute it and observe the touch-wheel controls in action.

Please refer to the XC82x User’s Manual for detailed description of the XC822T product.

1.1 Overview

The topics covered in this application note:

• Color Wheel features

• Software:

– Implementation details of Color Wheel software code

– Overview flow chart

– User-defined parameters

– Modify and Compile code using DAvE-Bench

– Download modified code using DAvE-Bench (XC800_FLOAD)

• Hardware:

– On-chip modules utilized

– Board schematic and layout

Figure 1 Color Wheel Application Kit

1) The steps and software code are also applicable for other XC82x/XC83x products that support capacitive touch control.

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AP08113

Capacitive-Touch Color Wheel Implementation

Color Wheel Features

Application Note 6 V1.0, 2010-08

2 Color Wheel Features

The Color Wheel board starts automatically when the kit is plugged into computer (via USB). This is indicated by

the ‘On/Off’ LED (see LED4 in Figure 6). When a finger moves over the touch-wheel, the software detects the

absolute position of the current finger touch and the color of the RGB LED (D2) changes accordingly. The effect

of the finger position depends on the selected color mode. There are three color modes available:

• Color (‘Hue’)

• Saturation (‘Sat’)

• Brightness (‘Light’)

The three color modes are represented by ‘Hue’, ‘Sat’ and ‘Light’ markings on the top of the respective LEDs as

shown in Figure 1 (or LED3, LED2 and LED1 respectively, as shown in Figure 6). The color modes can be

selected by tapping the centre button. Successive taps on the button cycle through the available color modes, so

the first tap selects ‘Sat’, the second selects ‘Light’ and the third selects ‘Hue’. The respective LED above the

touch-wheel will indicate the current color mode selection.

The main LED is a 3-channel RGB LED (D2), where the color is a combination of the three channels’ relative RGB

values, which are controlled by the PWM signals. When the Color Wheel board is in Color mode, a touch detected

by the touch-wheel will adjust the color aspect. The saturation and brightness aspects remain unchanged, until

the respective Saturation or Brightness mode is selected. The three modes set the HSL (Hue, Saturation,

Lightness) color space, which is converted into RGB space, which is fed into the RGB LED via 3 PWM signals.

The user can therefore adjust the light colors with the touch-wheel and centre button. Please refer to the

Section 3.3 for more details.

The Color Wheel board can be switched off with a continuous press of the centre button (~2s). The ‘On/Off’ LED

indicates the status. When off, the touch-wheel is inactive. Press the centre button again to turn the board on. The

current color mode selection is reset to ‘Hue’ and the RGB LED is reset to the default value.

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AP08113

Capacitive-Touch Color Wheel Implementation

Implementation of Color Wheel Software

Application Note 7 V1.0, 2010-08

3 Implementation of Color Wheel Software

The Color Wheel software enables some XC822T device functions, such as Real-Time Clock, Power Down Mode

and LEDTSCU for example. When the Color Wheel board is turned off, it actually enters Power Down Mode. The

device will wake-up every 1 second for less than 500µs, to check if a touch is detected on the centre button. If no

touch is detected, Power Down Mode is re-entered. When a touch is detected, the device will initialize all

parameters and jump to software execution from the main routine. The Color Wheel software flowchart is shown

in Section 3.4.

3.1 Touch Detection Methodology (using Touch-Wheel and LEDTS ROM Library)

The LEDTS ROM Library is enabled, with a customized trip point for touch detection threshold and an oscillation

window for the 4 touch-sense inputs. The centre button uses the TSIN3 touch-sense input, while the touch-wheel

is made up of 3 touch-sense inputs, TSIN0, TSIN1 and TSIN2, as shown in Figure 2. The 4 touch-sense inputs

are represented by bit 3-0 of the output parameters (PADFLAG, PADRESULT and PADERROR) of the LEDTS

ROM Library, FINDTOUCHEDPAD function.

There are two touch detection methodologies used in the Color Wheel Application Kit:

• LEDTS ROM Library touch detection methodology

• Touch-Wheel Library (Library_TouchWheel.lib) touch detection methodology

The centre button uses the LEDTS ROM Library touch detection methodology, while the touch-wheel uses the

Touch-Wheel Library touch detection methodology, as described in Section 3.1.1 and Section 3.1.2 respectively.

Figure 2 Four touch-sense inputs of Color Wheel Application Kit

Note: TSIN3, TSIN0, TSIN1 and TSIN2 are named WHEEL_C, wheel1 (WHEEL_1), wheel2 (WHEEL_2) and

wheel3 (WHEEL_3) respectively, as shown in the diagrams in Figure 2 and Figure 7.

3.1.1 Touch Detection Methodology for the Centre Button

The LEDTS ROM Library is used to detect a touch on the centre button. The outputs of the FINDTOUCHEDPAD

function show whether the centre pad is being touched; i.e. PADRESULT.3 = 1 indicates that the centre pad is

being touched, and the color mode and its respective LED will be updated accordingly.

Touch Detection Methodology by

LEDTS ROM Library:

- PADRESULT (Bit 3 – TSIN3)

- PADERROR (Bit 3 – TSIN3)

- PADFLAG (Bit 3 – TSIN3)

-PDCvalue

Touch Detection Methodology by

Touch- Wheel Library and

parameters from LEDTS ROM

Library:

- AVERAGEL/H of TSIN0, TSIN1

and TSIN2

- User’s inputs for Touch-Wheel

Library

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AP08113

Capacitive-Touch Color Wheel Implementation

Implementation of Color Wheel Software

Application Note 8 V1.0, 2010-08

The pad detection period depends on many parameters, such as the number of pad turns and LED columns

enabled and the accumulation of SFR LTS_TSVAL for example. The ‘All Enabled Pads Accumulated Count

Period’ (AEPACP) is 8.96ms, as defined in Equation (1). The ShortCount determines the minimum ‘valid pad

detection period’ (VPDP). The minimum valid pad detection period is 71.68ms, calculated as shown in

Equation (2).

(1)

where:

• TFD is Time Frame Duration = (((PREscaler x 256)/fCLK) x (Number of Time Slice(s))) = ((42 x 256) / 48MHz)

x 2 Time Slices = 448µs

• Number of Touch-sense inputs is 4

• AccumulatorCounter is defined as 4 in the software code.

(2)

where:

• ShortCount is defined as 0xF8 in the software code

A long touch on the centre button is detected when both PadDownCounter (PDC) is 0x40 and PADFLAG.4 is 1.

This long touch period is 1.71s, defined in Equation (3). If a longer detection period is required, modify PDC to a

smaller value.

(3)

The maximum valid pad detection period is 2.28s, as defined in Equation (4). For this period, the code can be

modified such that PADERROR.3 = 1, indicates a long touch on the centre button.

(4)

Note: PDC is used to keep track of how long the pad is touched. PDC is initialized to be 0xFF at the start of a

detected pad touch, and is decremented once at each All Enabled Pads Accumulated Count Period

(AEPACP). When pad touch is removed, PDC is compared with the user input value, ShortCount, and/or

0x00 to decide if pad touch is valid, invalid or a long touch. PDC is one of the parameters stored in XRAM,

at address 0xF0FF, by the FINDTOUCHEDPAD function.

Note: Please refer to LEDTS ROM Library in the User’s Manual for more details of the FINDTOUCHEDPAD

function, its inputs and its formulas.

3.1.2 Touch Detection Methodology for the Touch-Wheel

The Touch-Wheel Library (Library_TouchWheel.lib linked into the application code and programmed in the flash

memory) is used to detect a touch on the touch-wheel. It is provided as a .lib file and is described in Section 3.2.

The Touch-Wheel Library makes use of the AverageL/H values calculated by the LEDTS ROM Library to

determine the absolute location of the current finger touch on the touch-wheel. In order to keep the averaging

active, the PADFLAG bits are cleared for touch-sense inputs TSIN0, TSIN1 and TSIN2.

AEPACP TFD Number of Touch-sense inputs TSIN[x]()×AccumulatorCounter 1+()×=

Minimum Valid Pad Detection Period (VPDP) 0xFF ShortCount–1+()AEPACP×=

Long Touch Period 0xFF PDC–()AEPACP×=

Maximum Valid Pad Detection Period (VPDP) 0xFF AEPACP×=

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AP08113

Capacitive-Touch Color Wheel Implementation

Implementation of Color Wheel Software

Application Note 9 V1.0, 2010-08

3.2 Touch-Wheel Library

The Touch-Wheel Library (Library_TouchWheel.lib) has 2 main functions - calc_touchwheel() and

calc_compensation(). The functions are described in this section.

3.2.1 Calc_Touchwheel() Function

The calc_touchwheel() function provides the status (i.e. whether touch-wheel is touched), the position (the

absolute position of the last touch on the touch-wheel) and the touch-wheel average value as described in Table 1.

3.2.2 Calc_Compensation() Function

The compensation value is one of the user-defined parameters for calc_touchwheel function (see Section 3.2.1).

The compensation values for Wheel1 and Wheel2 are calculated with respect to Wheel3, as shown in

Equation (5) and Equation (6), to ensure that all values are equal under idle (no touch) condition.

(5)

(6)

Table 1 Specification of the Touch-Wheel Library Function - calc_touchwheel()

Function Name calc_touchwheel

Prototype void calc_touchwheel (int idata *parameter, char idata *angle, unsigned int idata *amplitude)

Input Address pointer of touch-wheel parameters (wheel_param[0])

The parameters include compensation for wheel2 and wheel1, amplitude threshold and filter

gain. Refer to Section 4.1 for descriptions of the user-defined parameters.

Address pointer of touch-wheel angle (wheel_angle)

The angle value is updated when the touch-wheel is touched

Address pointer of touch-wheel amplitude (wheel_amplitude[0])

The amplitude includes the touch-wheel position and the touch-wheel initial average value.

Refer to Section 4.1 for descriptions of the user-defined parameters.

Return None

Output Touch-wheel Status (wheel_amplitude[0])

00HThe touch-wheel is not touched

>00HThe touch-wheel is touched

Touch-wheel Position (wheel_angle)

This value is updated by the Touch-Wheel Library when the touch-wheel status is more than

0x00 (i.e. a touch is detected on the touch-wheel). The HSL value is updated accordingly

Touch-wheel Average Value (wheel_amplitude[1])

This value is calculated and updated by the Touch-Wheel Library when the touch-wheel is not

touched

Max Stack size 2

Resource used XRAM address 0xF0F6 - 0xF0FF (10 bytes)1)

1) These parameters are stored by the FINDTOUCHEDPAD function and are used to calculate the Average value for the

touch-sense inputs.

COMPENSATION_WHEEL2 AVERAGEL/H of WHEEL3()AVERAGEL/H of WHEEL2()–=

COMPENSATION_WHEEL1 AVERAGEL/H of WHEEL3()AVERAGEL/H of WHEEL1()–=

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AP08113

Capacitive-Touch Color Wheel Implementation

Implementation of Color Wheel Software

Application Note 10 V1.0, 2010-08

The calc_compensation() function provides the compensation values for Wheel1 and Wheel2 as described in

Table 2. The user can call this function during board calibration to obtain an estimation of the compensation

values. The values can be programmed to observe the sensitivity of the touch-wheel and further refined by the

user. This function should be called after an initialization period to get a stable value. Suggested initialization

period is about 640 Time Frame duration or interrupt and it can be calculated from Equation (7).

(7)

where:

• Divisor n is defined as 2

• AccumulatorCounter is defined as 4

• Number of Touch-sense inputs [TSIN(x)] is 4

• TFD is the Time Frame Duration

3.3 RGB LED

Figure 3 shows how the touch detection on the touch-wheel (based on the color mode) is reflected on the RGB

LED (D2). The HSL value is obtained from the Touch-Wheel Library, converted to an RGB value (via the

HSL_TO_RGB function), and the CCU6 registers are programmed where their respective pins are connected to

the RGB LED.

Figure 3 HSL to RGB LED Block Diagram

Table 2 Specification of the Touch-wheel Library Function - calc_compensation()

Function Name calc_compensation

Prototype void calc_compensation (int idata *compensation)

Input Address pointer of touch-wheel parameters (compensation[0])

The parameters include the compensation for wheel2 and wheel1.

Return None

Output Wheel2 Compensation Value (compensation[0])

The Compensation_Wheel2 value with respect to Wheel3

Wheel1 Compensation Value (compensation[1])

The Compensation_Wheel1 value with respect to Wheel3

Max Stack size 2

Resource used XRAM address 0xF0F6 - 0xF0FF (10 bytes)1)

1) These parameters are stored by the FINDTOUCHEDPAD function and are used to calculate the Average value for the

touch-sense inputs.

Period 2>Divisor n 8 AccumulatorCounter 1+()×× Number of Touch-sense inputs()TFD××

HSL Color Space RGB Color Space

R value

CCU6

G value

B value

HSL_TO_

RGB()

CC60SRLH

CC61SRLH

CC62SRLH

H value

S value

L value

Touch-wheel and centre button

RGB LED (D2)

PWM

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