LVDS Backlight when module in OFF state

Technical Support
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1

Hi,

I’m trying to power off backlight when Verdin module goes to “Module Off” state. After I issue a “shutdown” command in Linux and keep power to the Mallow carrier, the module goes to off state but backlight is still active on the LCD. Even if I manually turn of backlight (echo 1 > /sys/class/…/bl_power), it will turn on again after reaching final state.

System:

  • SoM: Verdin iMX8 MP 2GB QC WB IT
  • Carrier: Mallow
  • Display: Toradex LVDS 10.1" + cap touch

Any ideas?

BR,
Diego

2

Hello @d.moimas ,
Which SoM and carrier board version are you using?
Also, which version of Torizon OS or reference image have you installed?

Best regards,
Josep

3

Dear @josep.tx ,

the hardware is the one described above (Mallow + iMX8MP QC 2GB WB IT).

The image:

  • with Torizon core built from Yocto, then customized with tcbuilder (attached yaml file), it works great.
  • with Yocto minimal (tdx-reference-minimal-image) from “latest” sources, with same device tree (mallow, wifi) and same overlay (panel touch lvds): it doesn’t work. even if i turn it off by running a script in “/lib/systemd/system-shutdown” it will turn on again just after last line on debug serial port. I can connect an oscilloscope anche check BL_EN signal compared to power control signals, if needed.

BR,
Diego
torizon_build.txt (1.6 KB)
tcbuild.yaml (4.7 KB)

4

Uhm,
I just had the same issue with Torizon. I’ll investigate it at let you know after Jan, 6th.

Thanks in advance and happy holidays

BR,
Diego

5

Hello @d.moimas ,
Do you have any updates on this topic?

Best regards,
Josep

6

Dear @josep.tx ,

sorry, I was out of office for longer than expected. I returned this week but I’ll resume testing on our Mallow next week.
BR,
Diego