imaginator

I currently have Habpanel running on a 7″ RPi display test rig in my current apartment. It’s nice to get stats and control things. But… the panel is too small, has a crappy viewing angle and HUGE bezel.

I’d like to build touch panels for each room that are flush with the wall, and have a small bezel. And are larger and…

Sorting out specs, I’m thinking of around a 12″ panel (~27cm × 15cm). Driven by a RPi or similar single board computer. Everything hidden away in the wall so that it’s literally just a panel built into the wall. Ideally the panel will sleep when not in use. Or show photos or… But we’re still on the hardware layer today. The fun software bits come later.

I found a supplier and received a quote for 10 touch panels for around $1000.

They look half decent:

Panel Model	LP125WF1-SPA3
Panel Brand	LG Display
Descrition	a-Si TFT-LCD ,12.5 inch, 1920×1080
Panel Type	a-Si TFT-LCD
Active Area	276.48×155.52 mm
Outline	301.4×192.5×6.18 mm
Shape Style	Slim (PCBA Flat, Depth ≤3.2mm)
Surface	Anti Fingerprint
Contrast Ratio	700:1 (Typ.)
Display Colors	262K (6-bit) , CIE1931 50%
Viewing Angle	80/80/80/80 (Min.)(CR≥10) (L/R/U/D)
Frequency	60Hz
Signal Interface	eDP (2 Lanes) , 40 pins
Input Voltage	3.3V (Typ.)

Then I started researching the Signal Interface part of the problem. Most modern panels come with eEP (Embedded DisplayPort). I had been thinking of driving the panels off netbooted Raspberry Pi Compute Modules. Both the compute modules and the Regular Pi’s come with the following display ports:

I had thought that DPI would be a way to go – but this only puts out analogue to a display, and I’d still need to convert it.

Serial Display Interface would be nice but it turns out the RPi uses a proprietary driver and setup that will only work with their official 7″ Panel.

And on the other end, eDP – quoted by someone far smarter than me as

‘while electrically identical to Displayport, does not use the standardized Displayport connector. every manufacturer has their own favorite connector which can vary from panel to panel. this is why all eDP hobby projects boil down to ‘how do i connect these super-high-speed RF signals from my Displayport connector to this crazy LCD panel connector?’
So at this point I’ve been looking at a rather janky HDMI to eDP converter and trying not to shudder. It does “2 lanes 30 pins” and the panel above is rated at 40 pins. Don’t ask me what that means, but I’d rather not be twiddling super-high-speed RF pins hoping for the right phase of the moon and for everything to work.

Then Rene mentioned Olimex and their single board products. It looks like they have some sensible display interfaces.

Next stop – investigate what Olimex can do.

Update:

Stuart Nelson suggested that I look at the Amazon Fire 10″ Tablet. They currently go for around $100 each and come with a decent spec. For this to work I’d also need a special cable that connects at right angles and is ribbon so that it can be routed behind the tablet holder on the wall.

I’m imagining the tablets being Ethernet connected (although probably will be on wifi (something I’m not wild about for HA control). But running power from the Ubiquiti ES/24/250W switch will help minimise cable mania. That then implies needing to get a POE > USB adapter.

For the moment I’ll order a used tablet to test on and also a ribbon cable from Alibaba. There’s still a few months to test all of this. :).

Then I just have to ask Rene for help 3D printing a test wallmount.

Update to the Update:

The new RockPro64 comes with a [modern] eDP connector. I’m excited… This would be much more fun than sticking Android tablets on the wall.