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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