For a modular system, the architecture is critically important, as it determines the platform's functionality and modularity. From the earliest conceptualisation of the project, I envisioned a system similar to the Adafruit Feather and SparkFun Qwiic ecosystems, which offer excellent modularity for prototyping. However, different systems come with their own pros and cons. The deeper I delve into various connector options, the more I realise it's challenging to find a generic connector that suits all purposes. That said, the discussion of connectors will be saved for another time.

While conducting research, I came across a Reddit post that caught my attention. One comment stated that Arduino PLCs combine the worst aspects of both the Arduino and PLC worlds, and I somewhat agree. Here's the link:

https://www.reddit.com/r/PLC/comments/145ukb4/arduino_opta_good_or_garbage/

Therefore, some of the most important features I want to incorporate are as follows:

- Modularity down to the HMI, IO, and MCU levels
- Expandability with multiple modules
- Form factor compatible with DIN rail casing for easy deployment, with potential for other mounting methods

In fact, it may resemble an Arduino Opta, but that's not the main focus. The emphasis is on hosting various modules with multiple functions within a unified casing. With that in mind, the following designs have been developed.