jasona99 wrote:2. I have no way to test this right now, but I have switched the HDMI cables with that of my monitor after the Pi boots with power from the Lapdock. The Pi fully boots and displays the login prompt, so the Pi has power. Side note: I plugged the Pi into my wall outlet and managed to get my Lapdock to start, and the same thing happened to the screen, it came on, then turned off after a few seconds.
3. The Pi is powered continuously.
4. Yes, the Pi works with other HDMI monitors.
I noticed that it sometimes takes a few tries before my Lapdock actually turns on, as if nothing is plugged in to the HDMI, so that could be a problem as well, or maybe a factor causing my problem. I also noticed that before it dies, my Lapdock's screen gets significantly brighter, this could be another thing contributing to the problem.
It could be something flaky with the Micro HDMI cable or more likely the adapter. Those things are really tiny and don't give a me lot of confidence. I'm puzzled about #2: the way an Atrix Lapdock detects that a phone (or RasPi) is plugged in is using the DDC/CEC ground line. [Gory details here.
] If it's pulled low (e.g., shorted to the other grounds by the phone or RasPi), then Atrix Lapdock powers on the Micro USB plug, and if Lapdock is open it also powers on the screen and Lapdock USB A ports. If you unplug the HDMI cable from RasPi so you can plug in a different HDMI cable to it, this should cause Lapdock to power off assuming it works the same as an Atrix Lapdock.
You might try skewing the Micro HDMI connectors a little and see if that makes a difference. There may be poor alignment somewhere.
The changing brightness behavior is a poser.
Another thing you might try is setting config_hdmi_boost
to a higher value, e.g., 4. This shouldn't make a difference since if it were too low HDMI shouldn't work at all, but it's an easy thing to try and does make a difference if the voltage is a little low.