Backlight Control (Woodpecker, Robin)
The backlight control signal (BKLTCTL) is located at pin B83 of the COM Express Connector, is intended to control the intensity of the backlight of the LVDS display.
The BKLTCTL signal is 3.3V CMOS compatible PWM output of the Intel US15W Chipset. The PWM frequency can be adjusted from 0Hz to 65'535Hz. Normally, the frequency values should be set between 300Hz and 1kHz.
If the back-light inverter features an analog 0 to 5V interface for controlling the intensity, the baseboard needs a 5V level shifter for the BKLTCTL signal and a suitable low pass filter.
The following section describes the enabling and adjusting of the BKLTCTL signal in the Intel Embedded Graphics Driver (IEGD) Configuration Editor.
- Create a new configuration or open an existing configuration
- Make sure that the LVDS port is selected under Port Devices and klick to Next
- Click on the button Attribute Settings
- Enable Intensity and enter a default backlight intensity value between 0% and 100%
- Enable Inverter Frequency and enter a suitable PWM frequency between 0Hz and 65535Hz
- Make sure that Backlight Method is set to PWM Mode
You will find more information about the Intel Embedded Graphics Driver here: http://www.intel.com/design/intarch/swsup/graphics_drivers.htm
Please take reference to the IEGD User's Guide for additional information about How To install the generated drivers to the desired Operating System.