Data Sheet

ManualsBrands4D Systems ManualsRaspberry Pi Accessories / HATs3.5" Primary Display for Raspberry Pi A+/B+/2

4D SYSTEMS 4DPi-35 Primary Display – Raspberry Pi Compatible

4DPi

-35

Primary Display

– Raspberry Pi

To turn the backlight off:

sudo echo 0 > /sys/class/backlight/4dpi-35-

pwm/brightness

To turn the backlight on (scale of 1 to 255):

sudo echo 255 > /sys/class/backlight/4dpi-

35-pwm/brightness

The same brightness parameter controls the

backlight for both on/off control and PWM

control. If the cmdline.txt file has PWM enabled

and the value of the brightness variable is set to be

1 or higher, the PWM on the Raspberry Pi

activates, 1 being very dim and 255 being full

brightness.

If the cmdline.txt file has PWM disabled and the

value of the brightness variable is set to 1 or

higher, the backlight will simply be on full

brightness.

Setting the brightness parameter to 0 in either

case will disable the backlight.

If GPIO18 is desired to be used for other purposes

(such as analog Audio), be sure to set the

cmdline.txt file to disable the PWM, and it will not

be used by the brightness parameter and

backlight.

Parameters Listing

The following is a list of all the custom parameters

used by the 4DPi-35.

rotate: Screen rotation 0/90/180/270 (int)

compress: SPI compression 0/1/2/3/4/5/6/7 (int)

pwm: PWM backlight control on GPIO18 1/0 (int)

product_code: Force product code (int)

sclk: SPI clock frequency (long)

Valid product codes are:

0xab - 4DPi-35 (3.5” 4D Systems Pi Display)

0xac - 4DPi-35 (3.5” 4D Systems Pi Display)

Valid SPI Frequency values (4dpi.sclk):

Values can be almost anything. This has been

tested up to 64Mhz. Common values would

include 64000000 (64MHz), 48000000 (Default),

32000000, 24000000 etc.

Valid Compression values (4dpi.compress):

0 (compression off)

1 (compression on, auto set based on sclk value)

2 (lowest), 3, 4, 5, 6, 7 (highest compression)

These parameters can be set or read from the

/boot/cmdline.txt file, and they can be read from

the /sys/modules/4dpi/parameters directory.

For example:

cat /sys/modules/4dpi/parameters/rotate

Will display the current value of the screen

rotation parameter.