Backlight BL_ON signal at power-on doesn't wait for stable pixel data

Shouldn’t the BL_ON wait until pixel data and clock signals are stable, before going active?
It appears to go active immediately at power on, resulting in a brief (100-200ms) flash of white on my LCD before splash screen is displayed.

Just as on Colibri Ev Board 3.2B, I wired BL_ON to drive the PWRDWN pin on the LVDS driver, as well as the enable pin on my backlight driver.
Same components as your ref design.

I use the default BL_ON pin SODIMM-71.

Colibri VF61 1.2A,
CE6 image 1.5

Bootloader is from same package
(how can I tell bootloader version after it’s installed???)


We are looking into it. Could you please wait for sometime. We will get back you soon.

If this is problematic to detect in the driver, a configurable delay after power-on would be a huge help, as I think the time for valid data to appear is pretty constant.


Thanks Andy, I added a pulldown for good measure. I look forward to that feature being implemented.

I’d like to mark the question as answered, but didn’t see the option.

Thanks for your help.

We created a feature request and will discuss next week, whether we can implement this option into the bootloader.

Please be aware that there is still a time between power-up and executing the bootloader code, when we don’t have software control over the backlight pin. It is probably floating and should be pulled to inactive state on your carrier board.

This option can be somehow useful;

I see that for “Display On/Off Gpio”, bootloader already has a “Display On Delay (ms)” setting (ss.dispondelay).

It’s only an idea, but mabe a ss.blondelay parameter could be a solution.

Dear @ebbe
We decided to implement a configurable delay for the BL_ON signal, as we have done it already on other platforms. We didn’t decide on a schedule yet.
Regards, Andy

That’s great news. Kudos to your dev team!

Thank you.

Dear Ebbe,

We implemented this feature and will be released in next version.

You can use early release to test it.

You can use ss.dispondelay parameter to delay backlight and display on pins. Setting is in milliseconds.

Have a nice day.