Axon - how to do brightness control - hdmi lcd

Tmd · August 4, 2026, 8:11am

lcd getting detected. but we can change brightness we got DDC fail

log -
root@vicharak:~# ddcutil detect
Invalid display
I2C bus: /dev/i2c-10
DRM connector: card0-HDMI-A-2
EDID synopsis:
Mfg id: YDK - UNK
Model: YD-Monitor
Product code: 10811 (0x2a3b)
Serial number: J257M96B00FL
Binary serial number: 16843009 (0x01010101)
Manufacture year: 2024, Week: 3
DDC communication failed

root@vicharak:~# ls /sys/class/backlight/
root@vicharak:~#

Avi_Shihora · August 4, 2026, 12:38pm

@Tmd, Could you send the output of below command !?

i2cdetect -y 10

Meanwhile, you can use xrandr.

xrandr adjusts display brightness software-side by altering color levels in your graphics card’s framebuffer—making it an effective tool for external monitors or displays without direct hardware backlight control.

Your command breaks down as follows:

--output HDMI-2: Targets the display connected to HDMI-2.
--brightness 0.7: Sets software brightness to 70% (scale is 0.0 to 1.0).
--gamma 0.45:0.34:4: Sets RGB color curves individually (Red = 0.45, Green = 0.34, Blue = 4.0). Note: High blue values will tint the screen heavily blue.

 xrandr --output HDMI-2 --brightness 0.7 --gamma 0.45:0.34:4

Tmd · August 4, 2026, 1:48pm


root@vicharak:~# i2cdetect -y 10
[  291.071407] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
[  291.071505] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
00:                         -- -- -- -- -- -- -- -- 
[  291.071559] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
[  291.071612] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
[  291.071661] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
30: 30 [  291.071710] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.071760] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.071809] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.071872] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.071922] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.071972] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.072021] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.072070] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.072118] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.072166] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.072214] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.072263] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.072313] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.072363] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.072412] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.072460] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.072509] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.072557] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.072606] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.072661] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.072677] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.072693] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.072708] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.072724] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.072742] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.072761] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.072778] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.072795] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.072811] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.072829] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.072846] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.072866] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.072884] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.072901] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.072918] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.073185] dwhdmi-rockchip fdea0000.hdmi: i2c read err!
[  291.187484] dwhdmi-rockchip fdea0000.hdmi: i2c read time out!
31 [  291.188212] dwhdmi-rockchip fdea0000.hdmi: i2c read err!
[  291.303488] dwhdmi-rockchip fdea0000.hdmi: i2c read time out!
32 [  291.304291] dwhdmi-rockchip fdea0000.hdmi: i2c read err!
[  291.419522] dwhdmi-rockchip fdea0000.hdmi: i2c read time out!
33 [  291.420333] dwhdmi-rockchip fdea0000.hdmi: i2c read err!
[  291.539335] dwhdmi-rockchip fdea0000.hdmi: i2c read time out!
[  291.539912] dwhdmi-rockchip fdea0000.hdmi: i2c read err!
34 [  291.651487] dwhdmi-rockchip fdea0000.hdmi: i2c read time out!
35 [  291.652342] dwhdmi-rockchip fdea0000.hdmi: i2c read err!
[  291.767492] dwhdmi-rockchip fdea0000.hdmi: i2c read time out!
[  291.767994] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
36 -- -- -- -- -- -- -- -- -- 
[  291.768062] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
[  291.768115] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
50: 50 [  291.768167] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.768218] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.768267] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.768319] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.768368] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.768438] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.768487] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.768537] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.768586] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.768635] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.768686] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.768736] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.768787] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.768837] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.768886] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.768935] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.768984] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.769033] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.769082] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.769131] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.769181] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  291.770192] dwhdmi-rockchip fdea0000.hdmi: i2c read err!
[  291.883527] dwhdmi-rockchip fdea0000.hdmi: i2c read time out!
51 [  291.884341] dwhdmi-rockchip fdea0000.hdmi: i2c read err!
[  291.999515] dwhdmi-rockchip fdea0000.hdmi: i2c read time out!
52 [  292.000327] dwhdmi-rockchip fdea0000.hdmi: i2c read err!
[  292.115509] dwhdmi-rockchip fdea0000.hdmi: i2c read time out!
53 [  292.116292] dwhdmi-rockchip fdea0000.hdmi: i2c read err!
[  292.231715] dwhdmi-rockchip fdea0000.hdmi: i2c read time out!
[  292.232300] dwhdmi-rockchip fdea0000.hdmi: i2c read err!
54 [  292.347614] dwhdmi-rockchip fdea0000.hdmi: i2c read time out!
[  292.348219] dwhdmi-rockchip fdea0000.hdmi: i2c read err!
55 [  292.459529] dwhdmi-rockchip fdea0000.hdmi: i2c read time out!
[  292.460103] dwhdmi-rockchip fdea0000.hdmi: i2c read err!
56 [  292.579480] dwhdmi-rockchip fdea0000.hdmi: i2c read time out!
[  292.580102] dwhdmi-rockchip fdea0000.hdmi: i2c read err!
57 [  292.691451] dwhdmi-rockchip fdea0000.hdmi: i2c read time out!
58 [  292.692248] dwhdmi-rockchip fdea0000.hdmi: i2c read err!
[  292.807568] dwhdmi-rockchip fdea0000.hdmi: i2c read time out!
59 [  292.808354] dwhdmi-rockchip fdea0000.hdmi: i2c read err!
[  292.923430] dwhdmi-rockchip fdea0000.hdmi: i2c read time out!
5a [  292.924205] dwhdmi-rockchip fdea0000.hdmi: i2c read err!
[  293.039463] dwhdmi-rockchip fdea0000.hdmi: i2c read time out!
5b [  293.040232] dwhdmi-rockchip fdea0000.hdmi: i2c read err!
[  293.151444] dwhdmi-rockchip fdea0000.hdmi: i2c read time out!
5c 5d 5e [  293.152795] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
5f 
[  293.152862] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
[  293.152915] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
70: -- -- -- -- -- -- -- --                         
[  293.152965] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
root@vicharak:~# [  293.153015] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  293.153064] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  293.153115] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  293.153163] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  293.153212] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  293.153261] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  293.153310] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  293.153358] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  293.153406] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  293.153453] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  293.153501] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  293.153548] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  293.153609] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  293.153662] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  293.153712] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  293.153762] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  293.153810] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  293.153860] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  293.153909] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data
[  293.153957] dwhdmi-rockchip fdea0000.hdmi: unsupported transfer 1/1, no data

we tried changing the brightness using xrandr but when we set to low brightness screen look more greeny…

when we run qt application then xrandr won’t be useful it showing can’t open display

root@vicharak:~# xrandr --output HDMI-2 --brightness 0.7 --gamma 0.45:0.34:4 
Can't open display :0
root@vicharak:~#