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Eurotech provides display timings for supported displays on request. For displays not yet
supported, Eurotech has a panel configuration service to create panel timings and cable drawings.
Contact Eurotech Sales for further details.
4.6.6
Brightness Control (Backlight)
Most LCD displays include one or more cold-cathode fluorescent lamp (CCFL) tubes to backlight
the displays. Some LCDs, such as passive transflective displays, can be viewed in daylight
without backlighting.
Panel backlights are driven by backlight inverters. These circuits are typically external to the
display and generate the several hundred volts required to drive the CCFL tubes. Backlights can
easily become the greatest source of power consumption in a portable system. Fortunately, most
backlight inverters include control signals to dim and turn off the backlight.
The BitsyXb supplies two signals for backlight control: Backlight PWM (J3.16) and /Backlight
On (J3.18). Backlight PWM is a filtered PWM signal that supplies an analog output voltage to
control the intensity of the backlight. The /Backlight On signal is an open-collector output to turn
the backlight on and off. The ADSmartIO controller drives these signals. See section 6.3.2 for
electrical specifications.
4.6.7
Contrast Control (Vee and Vcon)
Vee and Vcon are used to control the contrast of passive panels. Many passive panels require a
positive or negative bias voltage in the range of fifteen to thirty volts to bias the passive LCD
display.
Some displays include a Vee generator and simply require a low-voltage analog signal to control
the contrast. The Vcon output is a PWM-controlled output that can be used for this purpose.
Electrical specifications for Vee and Vcon are listed in section 6.3.2.
4.6.8
Touch Panel
The BitsyXb supports four and five-wire analog resistive touch panels (five-wire control is a
volume production option). Connect the touch panel to the inputs on connector J3. The touch
panel controller can wake the system from sleep (section 5.3.3). Electrical details are listed in
section 6.3.3.
