• ADP8870

• ADP8870DBCB-EVALZ

Backlight:

• Ambient Light Sensor Support (ALS)
• Five programmable ambient light sensing zones for optimal backlight power savings
• PWM input can be used for Content Adaptive Brightness Control (CABC) of any, or all, of the LEDs (PWM input scales the LED output current)
• Configurable Fade On/Off times
• Configurable Fade Law functions
• Configurable ALS filter settings
• Configurable Brightness/Intensity in 128 steps

LED:

• Up to 7 LEDs configurable
• Configurable Fade On/Off times
• LED Blink On/Off times
• Configurable Fade Law functions
• Configurable Brightness/Intensity in 128 steps from [0..255]

With the ADP8870 driver installed, you will find sysfs files in the
/sys/class/backlight/adp8870_bl/
directory. You will be able to query and set the current screen
brightness:

brightness

get/set screen brightness (an integer between 0 and 126)
writing 127 will enable the Ambient Light Sensor.

actual_brightness

reading from this file will query the HW to get real brightness value.

max_brightness

the maximum brightness value.

bl_power

Current FB Power mode (0: full on, 1..3: power saving modes; 4: full off).

The ADP8870 features 5 individually programmable Ambient Light Sensing Zones:

l1_daylight_dim

Ambient Light Zone Daylight: Backlight DIM Intensity (an integer between 0 and 127, typically set to 0).

l1_daylight_max

Ambient Light Zone Daylight: Backlight Intensity (an integer between 0 and 127).

l2_bright_dim

Ambient Light Zone Bright: Backlight DIM Intensity (an integer between 0 and 127, typically set to 0)

l2_bright_max

Ambient Light Zone Bright: Backlight Intensity (an integer between 0 and 127)

l3_office_dim

Ambient Light Zone Office: Backlight DIM Intensity (an integer between 0 and 127, typically set to 0)

l3_office_max

Ambient Light Zone Office: Backlight Intensity (an integer between 0 and 127)

l4_indoor_dim

Ambient Light Zone Indoor: Backlight DIM Intensity (an integer between 0 and 127, typically set to 0)

l4_indoor_max

Ambient Light Zone Indoor: Backlight Intensity (an integer between 0 and 127)

l5_dark_dim

Ambient Light Zone Dark: Backlight DIM Intensity (an integer between 0 and 127, typically set to 0)

l5_dark_max

Ambient Light Zone Dark: Backlight Intensity (an integer between 0 and 127)

ambient_light_level

Get conversion value of the first light sensor. This value is updated every 80 ms
(when the light sensor is enabled). Returns integer between 0 (dark) and 8000 (max ambient brightness)

ambient_light_zone

Get/Set current Ambient Light Zone. Reading returns integer between 1..5
(1 = Daylight, 2 = bright, …, 5 = dark). Writing a value between 1..5 forces the Backlight controller
to enter the corresponding Ambient Light Zone. Writing 0 returns to normal operation.

LEDs not assigned to the Backlight are optionally exposed to the Linux LEDs Class.

The LED class allows control of LEDs from userspace. LEDs appear in /sys/class/leds/. The brightness file will set the brightness of the LED (taking a value 0-255). The LEDS class also introduces the optional concept of an LED trigger. A trigger is a kernel based source of led events, such as ide-disk or backlight control.
For more information read linux/Documentaion/leds-class.txt

brightness

get/set LED brightness (an integer between 0 and 255)

max_brightness

the maximum brightness value.

#include 

static struct i2c_board_info __initdata bfin_i2c_board_info[] = {
#if defined(CONFIG_BACKLIGHT_ADP8870) || defined(CONFIG_BACKLIGHT_ADP8870_MODULE)
	{
		I2C_BOARD_INFO("adp8870", 0x2B),
		.platform_data = (void *)&adp8870_pdata,
	},
#endif
}

Configure kernel with “make menuconfig” (alternatively use “make xconfig” or “make qconfig”)

Device Drivers  --->
	Graphics support  --->
		[*] Backlight & LCD device support  --->
			<*>   Lowlevel Backlight controls
			   Backlight Driver for ADP8870 using WLED

There is no dedicated Blackfin STAMP evaluation board for the ADP8870. During test and driver development we used the ADP8870 Evaluation Mother/Daughter Board.

It can be easily wired to the Blackfin STAMP TWI/I2C header.

Leave J31 and J32 open (these jumpers connect the SCL and SDA to the cypress chip used as USB bridge). Then apply your own SCL, SDA, and GND to the big J30 connector on the left edge of the board.

The ADP8870 chip still needs Vin (to power the chip), Vddio (to pull nRST and nINT high), and Vboard (to power the ALS sensor on the daughter card). These are provided through the USB port and then get regulated down (Vin becomes 3.6V, Vddio is 2.7V, and Vboard is around 4 V). So even though you won't be using the USB to program the part, it would still be easiest to plug the board into a USB port just to power Vin, Vddio, and Vboard. Of course, if you want, you can power these supplies from a lab bench power supply. In that case, move LK1, 2, and 3 to the “EXT” position and apply the signals to J29.

ADP8870 driver is build as a module

root:/> modprobe adp8870_bl
adp8870_bl 0-002b: Rev.0 Backlight
Registered led device: adp8870-led7
root:/>

root:/> cd sys/class/backlight/adp8870_bl/
root:/sys/devices/platform/i2c-bfin-twi.0/i2c-adapter/i2c-0/0-002b/backlight/adp8870_bl> ls -l
-r--r--r--    1 root     root         4096 Jan  1 03:29 actual_brightness
-r--r--r--    1 root     root         4096 Jan  1 03:29 ambient_light_level
-rw-rw-r--    1 root     root         4096 Jan  1 03:29 ambient_light_zone
-rw-r--r--    1 root     root         4096 Jan  1 03:31 bl_power
-rw-r--r--    1 root     root         4096 Jan  1 04:55 brightness
lrwxrwxrwx    1 root     root            0 Jan  1 03:29 device -> ../../../0-002b
-rw-rw-r--    1 root     root         4096 Jan  1 03:29 l1_daylight_dim
-rw-rw-r--    1 root     root         4096 Jan  1 03:29 l1_daylight_max
-rw-rw-r--    1 root     root         4096 Jan  1 03:30 l2_bright_dim
-rw-rw-r--    1 root     root         4096 Jan  1 03:29 l2_bright_max
-rw-rw-r--    1 root     root         4096 Jan  1 03:30 l3_office_dim
-rw-rw-r--    1 root     root         4096 Jan  1 03:29 l3_office_max
-rw-rw-r--    1 root     root         4096 Jan  1 03:31 l4_indoor_dim
-rw-rw-r--    1 root     root         4096 Jan  1 03:29 l4_indoor_max
-rw-rw-r--    1 root     root         4096 Jan  1 03:31 l5_dark_dim
-rw-rw-r--    1 root     root         4096 Jan  1 03:29 l5_dark_max
-r--r--r--    1 root     root         4096 Jan  1 03:29 max_brightness
drwxr-xr-x    2 root     root            0 Jan  1 03:29 power
lrwxrwxrwx    1 root     root            0 Jan  1 03:29 subsystem -> ../../../../../../../../class/backlight
-rw-r--r--    1 root     root         4096 Jan  1 03:29 uevent
root:/sys/devices/platform/i2c-bfin-twi.0/i2c-adapter/i2c-0/0-002b/backlight/adp8870_bl>

root:/sys/devices/platform/i2c-bfin-twi.0/i2c-adapter/i2c-0/0-002b/backlight/adp8870_bl> echo 42 > brightness

root:/sys/devices/platform/i2c-bfin-twi.0/i2c-adapter/i2c-0/0-002b/backlight/adp8870_bl> cat brightness
42

root:/sys/devices/platform/i2c-bfin-twi.0/i2c-adapter/i2c-0/0-002b/backlight/adp8870_bl> echo 127 > brightness

root:/sys/devices/platform/i2c-bfin-twi.0/i2c-adapter/i2c-0/0-002b/backlight/adp8870_bl> cat ambient_light_level
1276

root:/sys/devices/platform/i2c-bfin-twi.0/i2c-adapter/i2c-0/0-002b/backlight/adp8870_bl> cat ambient_light_zone
4

root:/sys/devices/platform/i2c-bfin-twi.0/i2c-adapter/i2c-0/0-002b/backlight/adp8870_bl> echo 22 > l4_indoor_max
22

root:/sys/devices/platform/i2c-bfin-twi.0/i2c-adapter/i2c-0/0-002b/backlight/adp8870_bl> cat l4_indoor_max
22

root:/> cd /sys/class/leds/adp8870-led7/
root:/sys/devices/platform/i2c-bfin-twi.0/i2c-adapter/i2c-0/0-002b/leds/adp8870-led7> ls -l
-rw-r--r--    1 root     root         4096 Jan  1 03:29 brightness
lrwxrwxrwx    1 root     root            0 Jan  1 03:29 device -> ../../../0-002b
-r--r--r--    1 root     root         4096 Jan  1 03:29 max_brightness
drwxr-xr-x    2 root     root            0 Jan  1 03:29 power
lrwxrwxrwx    1 root     root            0 Jan  1 03:29 subsystem -> ../../../../../../../../class/leds

root:/sys/devices/platform/i2c-bfin-twi.0/i2c-adapter/i2c-0/0-002b/leds/adp8870-led7>echo 99 > brightness

root:/sys/devices/platform/i2c-bfin-twi.0/i2c-adapter/i2c-0/0-002b/leds/adp8870-led7> echo 0 > brightness

root:/sys/devices/platform/i2c-bfin-twi.0/i2c-adapter/i2c-0/0-002b/leds/adp8870-led7> cat max_brightness
255
root:/sys/devices/platform/i2c-bfin-twi.0/i2c-adapter/i2c-0/0-002b/leds/adp8870-led7>