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LCD brightness control on da850/omap-l138

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On da850/omap-l138 based boards LCD backlight is connected to:

  • GPIO2[15]/eCAP on variant 0 Logic PD EVMs.
  • GPIO2[15]/eHRPWM on SpectrumDigital variant 1 EVM and on Rev3 Logic PD EVMs.

Enabling PWM backlight

Follow below steps to enable PWM backlight on 03.22 based releases:

  1. Disable SPI as SPI flash chipselect line shared with backlight.
  2. Enable eHRPWM as specified here
  3. Then enable PWM backlight driver as below:
    Device Drivers  --->
    	 Graphics support --->
    	 	 [*]Backlight & LCD device support --->
    			<*> Lowlevel Backlight controls;
    	 	 	 	<*> Generic PWM based Backlight Driver

Steps to verify brightness control

# echo <brightness_value> > /sys/class/backlight/pwm-backlight/brightness

brightness_value can be varied from 0-250. 0 corresponds to 0% dutycycle and 250 corresponds to 100%.