Building a hardware watchdog timer for a kiosk or other system that needs to run 24x7 - version 2.0

My previous post covered a first version of a watchdog timer that I used in the past for another project. 

You may check it here.

As I mentioned there, I suspected that a somewhat different design would be necessary, because the target device could not have either GPIO pins available for allowing a keep-alive signal to be sent to the watchdog timer, or even if it had, it would be unlikely that the underlying linux OS on the Android system could not have the necessary drivers or support for changing the output of such pins.

Building a hardware watchdog timer for a kiosk or other system that needs to run 24x7

It was proven by Alan Turing back in 1936 that the halting problem applies for computing in general, and our contemporary computing machines are no exception.

Would predicting the crashing of an algorithm or program be a possible function, and we would be able to know the edge cases that cause an application to fail or enter a loop, without having to explore the actual scenarios to find these edge cases. To put it simply we would only have to ask the algorithm in which conditions it would enter a loop or end unexpectedly, and by not providing these inputs we would with absolute certainty not enter these scenarios.

Building a kiosk for Home Assistant from scrap parts - Part 2

With a project of this type, the hardware preparation is just the tip of the iceberg. It was thoroughly explained in the last post, despite one last change still being pending. What lacks is basically the addition of a resistive touch panel to the front of the screen, in order not to depend on the mouse as a pointer/input device. The panel is still somewhere between China and my location..

The first aspect that I found important to cover, now that I had this Android based kiosk up and running, was the ability to remote control it and launch arbitrary applications and services on startup.

Building a kiosk for Home Assistant from scrap parts

It is great to have automation in the house providing increments of comfort such as eliminating manual tasks like cleaning the floor, or to aid in managing the energy consumption by turning off lights and appliances which are not in use, or in the safety side, by providing intrusion detection or monitoring the presence of gas leaks or other hazards, and executing the adequate actions.

Tasmota-based multi-channel air quality sensor station

The sense of smell is an amazing function in vertebrate animals. Even the human nose, which is not particularly notable in comparison with other animals, is fascinating in its sensitivity to trace amounts of a large variety of substances. It has a level of selectivity and capability of distinguishing between different kinds of smells, which is very difficult to match by even the most sophisticated artificial sensors.

Having as the main motivation the enrichment of the IoT gadgetry sitting around in my house (and eventually fill up an entire 192.168.1.1/24 network address range), I found that (after the motion and entrance detection device), an interesting device to invest time on would be something capable of sensing multiple air quality parameters at the same time.

Trying to make the most out of Home Assistant + rooted Xiaomi vacuum cleaner + Valetudo

After some time using HA (Hass.io), and even longer using the Xiaomi Roborock (first generation) vacuum cleaner, I kind of felt a certain discomfort in keeping this robot in a stock setup. Sticking to the original firmware meant having a device that is permanently connected to a chinese cloud service, and without the user awareness it sends many megabytes of data daily to this service. Also it meant that integration and features via a platform such as Home Assistant, are limited.

One feature that I fancied for some time was the ability to define zones, and instuct the robot to go to these predefined zones on demand.

Ghost switching can be a bitch if your switch is your main circuit breaker

On my way to eat my own dog food, I learned the hard way that ghost switching is kind of the default problem most people will stumble upon when setting up their MQTT switch for the first time.This is not a big deal when you are configuring a single light switch or some other not so critical appliance. But when your switch is in series with your main circuit breaker, ghost switching suddenly gains a whole different level of importance.