Re: FACE module hardware design questions (LVDS, eDP and oth
Posted: Wed Oct 31, 2012 9:16 pm
I'm sorry, I've made a mistake and parts of my last post are no longer true.
The mistake was that I was measuring the DDC lines relative to GND which of course does not work because DDC is I²C and therefore open-collector based.
If I measure them from the 5V rail (for example) I can see that they have their 3.3V pull-up.
I've managed to get the LVDS display detected at boot by adding pull-ups to 3.3V to the DDC lines.
When I pull them down to GND or let them float the LVDS output is not activated.
This is what I needed.
It seems to only work at boot, so it is not "hot-plugging" but that's no problem for me.
What I haven't tested today is if there are actual signals on the DDC and LVDS lines but I will do that in a few days.
Thank you again for the good support!
-- Florian
The mistake was that I was measuring the DDC lines relative to GND which of course does not work because DDC is I²C and therefore open-collector based.
If I measure them from the 5V rail (for example) I can see that they have their 3.3V pull-up.
I've managed to get the LVDS display detected at boot by adding pull-ups to 3.3V to the DDC lines.
When I pull them down to GND or let them float the LVDS output is not activated.
This is what I needed.
It seems to only work at boot, so it is not "hot-plugging" but that's no problem for me.
What I haven't tested today is if there are actual signals on the DDC and LVDS lines but I will do that in a few days.
Thank you again for the good support!
-- Florian