I have a ton of unnecessary home automation, but I'm lacking some kind of house board: a quick way of getting info before leaving (like weather, or transport conditions), leaving messages (don't forget to pick up kids from school) or just a shopping list. Sensible people would look at readily available digital signage solutions. Of course I didn't do that, instead decided to build my own.
I settled for a quick list of requirements to guide the project: Linux based, running off power-over-ethernet, with net-boot and 100% locally hosted. How hard can that be?
The first step to design my houseboard was searching for a panel. Here is a capture of the moment it failed:
Turns out that scoring a random replacement panel for a laptop and trying to pair that with a random controller board works well in theory but needs a lot of luck. Starting with a cheapish £40 LCD panel with an eDP connector, I got an HDMI-to-eDP board. My panel and my board didn't like each other, so all I got was backlight, and that is not very useful unless you only need to display binary information.
Since ordering and shipping a different panel controller board would take a few weeks, I decided to change my strategy: my P0 would be changed to a Prototype-Prototype-0 (PP0), using a similar platform to let me start working on the software and sensors, while I figured the way to control a panel. Here is Houseboard PP0, in all it's glory:
I got a USB-powered touchscreen, which is powered by a RaspberryPi 4. The RPI itself is powered over PoE, and there is an HDMI connection between the Rpi and the screen, and a secondary USB connection to get touch screen support. The PoE adapter is barely capable of powering the screen AND the Rpi: if I turn the brightness of the screen to 100%, the system will reset.
And with a few sensors (a PIR + mmWave):
It's not going to win any design prizes, but it works
While eventually I did end up solving my LCD panel woes, Houseboard PP0 let me start building some software for the houseboard quickly:
- A Wayland based image display built on top of Swayimage; to show a gallery of pictures when there is no other info to show
- A presence service (to determine when there are humans nearby, based on PIR and mmWave sensors).
BoM for Houseboard PP0
- A RaspberryPi 4 (any Pi will do, but having a bunch of USB ports makes this project a lot simpler)
- A USB powered screen. I went for a 14'' 1080p 1920x1080, and with the PoE constrain that's probably as big as it's feasible. My browsing history says I got this one: https://www.amazon.co.uk/dp/B0CB5FWGT8
- PoE splitter (USBC + ETH out, 5v 4A) - Look for the adapter with largest power rating you can, a cheap one won't work. I went for this one: https://www.amazon.co.uk/dp/B0CHW5K5F4
- PIR sensor (NB VCC=5v, connect to Pin4, GND Pin6, OUT Pin17)
- Smaller PIR sensor (VCC=5v Pin4, GND Pin6, OUT Pin17)
