Increasing HDMI Boot Time

[sjunkie]

Hello,

I’m trying to create a delay (2 seconds) in starting the HDMI as it seems that our monitor is not ready when the board sends the initial signal (see the post below for details).

Dragon board 410c hdmi startup on win iot

We have a dragon board 410c running win IOT with the default app running. It is connected to an HDMI touch screen. We notice the following behavior: If the HDMI screen is powered up first; when the dragon board powers up windows boots up and displays on the screen just fine. However if both are powered up simultaneously, or if the dragon board is powered up first, then the dragon board does not show any output on the screen. Is this a known behavior? If so, is there a software level switc…

We are using Windows IoT - any thoughts as to how to accomplish this?

Regards,
Tina

[ljking]

The DragonBoard 410c does not generate the Hot Plug Detect signal. The DragonBoard generates a +5V signal that is sent to the monitor. The Monitor then responds by asserting the Hop Plug detect signal. The hot plug detect signal is generated by your monitor. The monitor should not generate the Hot Plug detect signal until it is ready.

I think you need to attach an Oscilloscope to the +5V, HPD, and DDC signals to determine why your monitor is generating a Hot Plug Detect signal before it is ready.

Full Disclosure: I am an employee of Qualcomm Canada, any opinions I may have expressed in this or any other post may not reflect the opinions of my employer.

[sjunkie]

Thanks @ljking

I had mistyped that - we want to find a way to delay the +5V signal that is sent by the board to the monitor until the monitor is ready to receive it.

My understanding is that if the monitor is not ready to respond when the 410c makes the query, so the 410c thinks there is no monitor attached.

A couple of other tests we ran:

• works fine if we apply power to the 410c (even by 1-2 seconds delay) after applying power to monitor
• does not work when powered at the same time. Tried several different brands of HDMI cables with same results

[ljking]

Hi @sjunkie

Unfortunately the hardware is not capable of delaying the HDMI_5V out signal. If you look at the Schematic for the 410c, on page 27 you will see that the main 5V power supply (SYS_5P0 which is used to boot the 410E processor) is routed into U14 (TPD13S523RSVR) and out to the HDMI connector. U14 is simply a current limiter, and ESD protection chip, it is not capable of switching the HDMI_5V signal on/off. This is fully in compliance with the HDMI specification, I believe it is your monitor that is non-compliant. Have you tried different monitors?

Full Disclosure: I am an employee of Qualcomm Canada, any opinions I may have expressed in this or any other post may not reflect the opinions of my employer.

[nigelman]

Yes. I have the same problem. I tested it with lots of monitors. I think it’s what sjunkie sais. Really, this is a big problem to build an embedded device.