HyperPixel no backlight?


#1

Hi, I have fresh retropie installation on Rpi2.
installed using script HyperPixel, and I can see text but hardly (backlight is not turned on)

tried this:

root@retropie:/home/pi# echo “0” > /sys/class/backlight/rpi_backlight/brightness
root@retropie:/home/pi# cat /sys/class/backlight/rpi_backlight/brightness
0
root@retropie:/home/pi# echo “1” > /sys/class/backlight/rpi_backlight/brightness
root@retropie:/home/pi# cat /sys/class/backlight/rpi_backlight/brightness
1

but no luck :(

chould I somehow additionally enable backlight?


#2

Just double check to make sure that "# Use a basic GPIO backlight driver with on/off support dtoverlay=hyperpixel-gpio-backlight"is definitely in your config.txt file.
You can find it in /boot.

This line should enable the generic backlight driver, so it’s possible that in your case it’s never being enabled.
Also, double check your GPIO connections to make sure they’re all making good contact!


#3

Thank you for the tip, it is enabled already :(

Is it possible that backlight is dead?

Here are the last lines of config:

Enable audio (loads snd_bcm2835)

#dtparam=audio=on
#gpu_mem_256=128
#gpu_mem_512=256
#gpu_mem_1024=256
#overscan_scale=1

HyperPixel LCD Settings

dtoverlay=hyperpixel
overscan_left=0
overscan_right=0
overscan_top=0
overscan_bottom=0
framebuffer_width=800
framebuffer_height=480
enable_dpi_lcd=1
display_default_lcd=1
dpi_group=2
dpi_mode=87
dpi_output_format=0x6f016
display_rotate=2
hdmi_timings=800 0 50 20 50 480 1 3 2 3 0 0 0 60 0 32000000 6

Use a basic GPIO backlight driver with on/off support

dtoverlay=hyperpixel-gpio-backlight


#4

That should be working fine!

I’d recommend checking you GPIO connections first, and if that doesn’t work, contact support@pimoroni.com to get a replacement unit sorted out.

It’s possible it got damaged during transport or instillation due to it being so fragile!


#5

it was packed nice, and installed carefully … maybe factory dead backlight :((


#6

Possibly!

Of course, there’s always the chance of a software fix.

Mr @Gadgetoid , I summon thee!


#7

I will check backlight pin on my Rigol scope…


#8

I’ve seen a couple with non-functioning backlights, but I’m not sure how they slip through since we’re testing the displays very thoroughly before shipping and the backlight isn’t particularly delicate. I have a display that I’ve removed from its metal shielding and separated into layers and the backlight still works.

Still, do double check that there isn’t something wrong with your backlight pin (BCM 19 iirc) and also verify you don’t have any other software which could be running and claiming this pin for its own purposes. If all else fails, let us know and we’ll sort out a replacement.


#9

Hey Gadgetoid, thank you for your answer! Just tell me, logic level should be high on BCM19 in order for backlight to be ON? I’ll check with scope, so I will eliminate “software” problems for sure…


#10

Hi Gadgetoid, I have just checked with scope,

if I type:
echo “0” > /sys/class/backlight/rpi_backlight/brightness
Voltage on BCM19 (pin 35) goes to logic low 0v

if I type:
echo “1” > /sys/class/backlight/rpi_backlight/brightness
Voltage on BCM19 (pin 35) goes to logic high 3v

TFT stays dark :( backlight is DOA

what should I do? Who to contact? Thank you


#11

Just tested with different OS (Raspbian) / different Raspberry (v3 instead of v2)… backight is dead :(


#12

Hi there Povezi!

Sorry to see that your screen is broken. :/

If you send an email to support@pimoroni.com asking for a replacement unit and give a link to this thread they’ll get you sorted out. :)

I hope your next one fares better!


#13

Thank you! I have just sent email…