home assistant wall mounted tablet

Home Assistant Wall Mounted Tablet Update

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This is an update to my previous post on my wall mounted Home Assistant tablet. There have been quite a few changes, so I thought it was worth another post on the subject. Let’s get into it…

Power Failure

I’ll start with the big issue which has plagued this project – power. Since the battery in the original tablet was completely exhausted I had built a wired power supply to replace it. Unfortunately, this wasn’t powerful enough and the tablet would power off sometimes under high load. This problem seemed to get worse until the tablet would power off after just a few minutes, thus becoming pretty much useless.

home assistant wall mounted tablet
The new PSU all wired up (difficult to capture in a photo!)

I mentioned previously that I had ordered a 5A power supply to fix this problem, but even that didn’t work. The tablet must pull transient currents of more than 5A, which a battery can supply quite easily. Unfortunately the fixed power supply cannot. This is a real shame because I put a lot of effort into the new power supply – I even printed a case for it based on a modified version of the parametric PCB case I used in my recent MySensors build.

Even with the failure of the new power supply, the exercise in building this has demonstrated the utility of a wall mounted tablet in our household. The decision was therefore taken to replace the old broken tablet with a new one.

The New Tablet

The new tablet is the Lenovo Tab E8 (link is to Amazon, but ours came from a local retailer), chosen solely because it was the cheapest 8 inch tablet available!

home assistant wall mounted tablet
The new tablet mounted on the wall, complete with new brackets

The tablet seems pretty good overall, at least for the price. The build quality is fine, although the case is very plastic-y. It’s a little slow after boot up as it loads up everything, but in normal usage as a wall mounted dashboard it performs perfectly well. The shipped operating system is Android 7.0, which is up to date enough to not present any problems with app support.

The biggest issue with this device is that it charges really slowly, even from the provided charger. I even had cases when setting it up that the battery would still drain when plugged in to the charger. I was a little concerned that the tablet battery would become discharged over time during normal use, due to wake ups from the motion sensing. However, once the tablet was mounted on the wall and left overnight it charged to 100% and has remained there since.

Fixing the Brackets

I printed new brackets for the tablet with a reduced front lip. This removes the issue with the brackets obscuring the screen. The right bracket (left from the point of view of the tablet and in the STL files) also has a cut out in it’s side to allow the USB cable to pass through. I made these edits in OpenSCAD, by first importing the original STL files. I then created an object which represents the material I wanted to remove. Then a difference operation between the two gives the final object. I’m pretty pleased with them. The only thing I wasn’t able to reproduce was the rounded internal edges on the cut out sections.

Wall Panel MQTT Integration

With the power issues solved, I can integrate the tablet fully with Home Assistant (without fear that the extra load will cause it to power off). I’ve integrated in the sensors available on this device (pretty much just the power status). The full YAML code for this is available on GitLab. This pretty much went according to the WallPanel documentation. However, I did find that I needed to specify a value_template in order to extract the battery value:

sensor:
  - platform: mqtt
    state_topic: "wallpanel/kitchen/sensor/battery"
    name: "Kitchen WallPanel Battery Level"
    unit_of_measurement: "%"
    value_template: '{{value_json.value}}'
    device_class: battery

To extract the boolean status for the charging state sensors, the template gets a little more complex:

binary_sensor:
  - platform: mqtt
    state_topic: "wallpanel/kitchen/sensor/battery"
    name: "Kitchen WallPanel Charge State"
    value_template: '{% if value_json.charging %}ON{% else %}OFF{% endif %}'
    device_class: power

  - platform: mqtt
    state_topic: "wallpanel/kitchen/sensor/battery"
    name: "Kitchen WallPanel AC State"
    value_template: '{% if value_json.acPlugged %}ON{% else %}OFF{% endif %}'
    device_class: plug

I also integrated in the motion, face detection and QR code sensors, although I’m not using the face detection or QR code sensors and have since disabled them in WallPanel.

sensor:
  - platform: mqtt
    state_topic: "wallpanel/kitchen/sensor/qrcode"
    name: "Kitchen QR Code"
    value_template: '{{value_json.value}}'

binary_sensor:
  - platform: mqtt
    state_topic: "wallpanel/kitchen/sensor/motion"
    name: "Kitchen Motion"
    payload_on: '{"value":true}'
    payload_off: '{"value":false}'
    device_class: motion

  - platform: mqtt
    state_topic: "wallpanel/kitchen/sensor/face"
    name: "Kitchen Face Detected"
    payload_on: '{"value":true}'
    payload_off: '{"value":false}'
    device_class: motion

The final integration I did was to add a switch to turn on and off the camera streaming. However, in general usage this seems a bit flakey, with the camera stream not usually becoming available until after a WallPanel restart. Here’s the YAML used for the switch anyway:

switch:
  - platform: mqtt
    command_topic: "wallpanel/kitchen/command"
    name: "Kitchen Camera State"
    payload_on: '{"camera": true}'
    payload_off: '{"camera": false}'
    optimistic: true
    retain: true

Dashboard Improvements

home assistant wall mounted tablet
My Current Dashboard

I’ve improved my dashboard somewhat since my last post. However, it’s still a long way from some of the awesome dashboards I’ve seen posted. It’s still a work in progress!

The main changes have been to switch to the animated weather custom card for the weather forecast and to add Custom Header to my install to compact the header. I then added more buttons, some media controls and a gauge showing the progress of my 3D prints. The vacuum buttons call some custom scripts to start the vacuum with our preferred settings. This is necessary to work around a bug in HASS with the Botvac D3:

script:
  spot_clean:
    alias: "Spot Clean"
    sequence:
      - alias: "Start spot clean"
        service: vacuum.neato_custom_cleaning
        data:
          entity_id: vacuum.marvin
          mode: 2
          category: 3

  house_clean:
    alias: "House Clean"
    sequence:
      - alias: "Start house clean"
        service: vacuum.neato_custom_cleaning
        data:
          entity_id: vacuum.marvin
          mode: 1
          category: 2

It should be noted that I’m running a slightly older version of HASS at the moment. In newer versions the service name changed to neato.custom_cleaning. Also, using a category value of 3 for spot cleaning appears to be undocumented, but if you look at the library, that’s what it’s doing.

Conclusions

This setup is now working perfectly and all the problems with the previous iteration have been resolved. It’s unfortunate that this was done by throwing money at the problems, but sometimes things just don’t work out as we hope!

Overall, I’m really happy with the finished product. The dashboard will be continually developing as I come up with ideas and work out what’s useful and what isn’t. Feel free to share your ideas again via the feedback channels.

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power supply connected

Salvaging a Broken Tablet for a Smarthome Dashboard

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I’ve never been massively convinced in the utility of a wall mounted smarthome dashboard. It’s always seemed like there are easier ways of controlling the smart home, for example Zigbee buttons. I guess one advantage could be their use as an information radiator for your home. However, I tend to have a good eye on what’s going on around the home and have notifications set up for all the important non-obvious stuff.

Basically, I was never convinced enough to go out and buy a tablet for this purpose. Especially as the decent tablets in NZ are pretty expensive, we don’t seem to get the cheap Amazon Fire ones which are popular for this application. However, the opportunity arose to use a defunct tablet for this purpose. So I thought I would give it a try – if I could get it to work.

Powering The Tablet

The tablet in question is a Samsung Galaxy Tab Pro 8.4, which is several years old and would not power on due to a completely exhausted battery. After doing a bit of research on YouTube, I was able to determine that it should be possible to disconnect the old battery and use the connector to power the tablet from the wall, with the cable running out through the back of the device.

Once I had the correct tools to pry apart the case without damaging the screen I was able to remove the battery without any problems. I then snipped off the connector on the battery, leaving enough cable to solder some new cables to the positive and negative terminals.

Then I built up a power supply to provide the required 3.8-4.2V via the battery connector. I used a small adjustable voltage regulator to provide power. As it turned out this wasn’t enough to power the tablet by itself. However it did power up when the USB cable was additionally attached.

power supply during testing
The power supply during testing
power supply finished
Power supply once finished off with tape and heatshrink
power supply connected
The power supply sitting in the battery cavity
cutting a hole in the back of the tablet
Since the power supply wouldn’t fit flush, I needed a larger hole than I originally intended in the back of the tablet!
taped up hole
There I fixed it!

Unfortunately, it’s still a bit flakey and will sometimes power off due to a brown out. It’s OK in normal (very light) use as a dashboard, but can’t cope with much more. I’ve ordered a power supply which can supply more current (up to 5A). Hopefully once I have that installed I can drop the USB cable and only need a single connection.

Mounting

I 3D printed the mounting brackets for the tablet from a ready made model. These brackets are nice and easy to print, however I found on installing the tablet that they obscure the bottom corners of the screen quite a bit. I also can’t rotate them so the short sides are along the bottom due to the USB connection. I’m hoping I’ll be able to modify the design in order to reduce the size of the bottom tabs, but I haven’t got around to this yet.

mounting brackets
The mounting brackets once mounted to the wall (they are level, I just can’t hold the camera straight!)

Updating the OS

Aside from the power issue, the main issue with this tablet being so old is the version of Android it was running – 4.4.2! This is pretty ancient and means a lot of apps aren’t available any more. Also the browser app which I wanted to use (WallPanel) uses Android WebView and the version available won’t render Home Assistant’s Lovelace UI. Unfortunately WebView isn’t upgradable in this version of Android either.

With all this in mind I set out to upgrade the tablet. I knew that it was supported by Lineage OS at some point in the past. With a bit of fiddling (and compiling Heimdall from source), I was able to get TWRP running on it. I then installed an old version of Lineage OS (13), OpenGApps Nano and Magisk on it. This gave me Android 6.0 and full root access. Not great, but not awful. I wouldn’t recommend this setup on a device your going to use as a daily driver, since it hasn’t had any security updates in a while.

Smarthome Dashboard and Other Apps

tablet smarthome dashboard
The tablet showing my smarthome dashboard so far

On that base, WallPanel (with an upgraded WebView) works great with HASS. I’ve also installed the prime version of Nova Launcher to give me a nice home screen for launching other apps from (I needed to prime version to scale up the icons for easier casual use). A secondary purpose of this tablet will be for firing things off to the Chromecast quickly without having to use one of our phones, so launching of Netflix and other streaming apps are required.

tablet launcher
The launcher with quick access to other apps

I really like WallPanel, especially the MQTT and camera integrations. However, I’ve currently got most of the advanced features turned off to save power and prevent brown outs! I really need to fix that power supply! I am making use of the motion detection to wake the tablet up though. Tasker and Termux are also installed, but I’m so far not doing much with them.

As you can see from the photos, I’ve begun work on a smarthome dashboard view in Lovelace for this, but I haven’t got too far. Part of the reason for this post is to get others to share their dashboards and give me some inspiration.

Conclusion

It seems like this project has had more than it’s fair share of issues and road blocks. I definitely wouldn’t call it finished, but the proof of concept is there and there is a clear path for what needs to be improved.

So far the tablet has been on the wall for a couple of days and I’m already finding it useful. Since the tablet will wake up as you walk past it will generally catch your eye and convey some useful information (such as when it’s going to stop raining!). I think I’ll focus on the informational/status aspect in my dashboard design going forward.

Next Steps

I’ve documented most of the next steps above, but as a recap:

  1. Replace the power supply with one that can provide more current;
  2. Modify the mounting bracket design to not obscure the tablet screen;
  3. Turn on the advanced features of WallPanel and integrate into HASS;
  4. Finish the Lovelace dashboard.

I’ll also probably do some more integration/automation using Tasker. One feature I would like would be to re-launch the dashboard when the tablet becomes idle, in case someone left it on a different screen.

I hope you’ve enjoyed following this journey of me giving new life to some old hardware. It’s always nice to do that rather than making yet more e-waste! Please feel free to share your own smarthome dashboard projects in the comments and feedback channels, I definitely need more inspiration.

If you liked this post and want to see more, please consider subscribing to the mailing list (below) or the RSS feed. You can also follow me on Twitter. If you want to show your appreciation, feel free to buy me a coffee.

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