April 3, 2023

GCP Ubuntu VM Freezing on Auto Updates

Upon migrating my blog to a Google Cloud Compute Engine VM (this very blog) I had a strange issue where it would freeze and become unresponsive. Only “Resetting” the VM would bring the blog back.

The findings were so interesting I thought I would share them.

Issue

It’s worth noting what the instance is (and importantly what resources it has been allocated) as it probably would not be an issue with a larger (and more expensive) instance. As of writing the instance is set to a “e2-micro” instance located in “us-central1”. The reason for this is you get one free instance in this region when using Google Cloud.

March 31, 2023

Pi Garage Relay Lock Up

After initial release with the Home Assistant mobile app performing the opening and closing it was observed that quick button presses (from my daughter pressing the button rapidly🤣) that this could cause a lock up of the hardware in a weird way.

You could see the lights on the relay change to show that the control signal to change the relay state was working however you could not hear the “click” of the relay. Other relays worked as expected, it was as though the relays themselves or something got “latched” in the changed state.

March 31, 2023

Open Source Repository Challenges

Making the project Open Source is a good thing as it allows others to learn from it but also to so that people can be assured that there is no nasty other software that is installed with the application.

However as anyone on the internet can view the source code this introduces complexities that you do not have with a private repository.

One main issue is that you cannot store configuration or credentials in the repository. Every configuration item (say an app store identifier) and credential item (Google Play Store publish token or API key) MUST come from repository secrets.

March 30, 2023

Pi Garage Realtime Communication

Pi Garage worked well for a while, however there was one thing that bugged me. When you would have 2 devices open on the home screen (in the mobile app) and you would open the door on one device the state would change from “closed” to “opening” to “open” but on the other phone it would still say “closed”.

This annoyed me as to get the latest state you constantly had to “swipe to refresh” to ensure that you had the latest state of the garage door. Not a big deal in the scheme of things but it was a good problem to solve.

March 30, 2023

Pi Garage Mobile App

Along with the backend part of Pi Garage I really wanted to have a mobile app (both iOS and Android) so that it would be easy for users to use Pi Garage without having to configure a 3rd party app (like Home Assistant) or via an API page (like Swagger).

I have had experience with React Native and found the experience akin to fingernails on chalkboard. I wanted to use something that had a better developer (and maintainer) experience.

March 30, 2023

Pi Garage Deployment

The next decision to make was how to deploy the backend application. I had many different ways that I could release the application. However there were some key considerations to make.

Ease of deployment (especially for target audience)
Versioned releases
Ease of rollback?

This lead me to consider the following.

NPM Package

As the backend is built in Node.JS it would be easy to just push the built packages to npm. Although this would get versioning and rollback I thought that this would be a pretty 💩 experience to deploy and run it.

March 30, 2023

Pi Garage Backend App Framework

As I had chosen to use a Raspberry Pi for the hardware this allows me to use any language and framework that I want as long as the Raspberry Pi supports it. To view the current Open Source code can see it here on GitHub.

I new that I wanted to write the app in Node.JS (my favourite) and to make my life easier I commonly use the application framework NestJS. This opinionated framework which is heavily inspired by Angular and it’s structure (and cli) allows you to build all sorts of applications quickly and easily.

March 30, 2023

Pi Garage Interface Board

For interfacing with the garage door I knew (from my one) that there was the ability to add a wired push switch to the garage door to “toggle” it. However I had no idea what voltage/current this used as it was not listed in the manual. I also knew that other garage doors would potentially have varying specifications regarding this. This meant I needed to find someway of using a relay with the Raspberry Pi instead of just using the GPIO straight to the garage door (in case of blowing up the Raspberry Pi).

March 30, 2023

Pi Garage Base Hardware

For the hardware I made it my mission to use as much common off the shelf components as I could that had a long supply life.

I recall an Open Source touch rotary switch that had a small LCD screen in the centre of it. I thought it looked like something that Tony Stark would have built. However there was one part (a major part at that) that was bought of Alibaba or something, I think it was the motor. This part was “off the back of a truck” so you couldn’t buy a replacement and other people couldn’t make one as well.